Provided by: yodl_2.13.2-1_i386 bug

NAME

       yodlbuiltins - Builtins for the Yodl converters

SYNOPSIS

       This manual page lists the standard builtins of the Yodl package.

DESCRIPTION

       The  following  list  shows the builtins defined by the Yodl converters
       define and which can be used in Yodl documents. Refer to the Yodl  user
       guide, distributed with the Yodl package, for a full description.

       The  following  list  shows all builtins of the package in alphabetical
       order.

       Yodl’s builtin commands
              As mentioned previously, YODL’s input consists of  text  and  of
              commands.  YODL supports a number of built-in commands which may
              either be used in a YODL document,  or  which  can  be  used  to
              create a macro package.

              Don’t  despair  if you find that the description of this section
              is too technical. Exactly for this  reason,  YODL  supports  the
              macro  packages  to  make  the  life  of  a documentation writer
              easier. E.g., see chapter [MACROPACKAGE] that describes a  macro
              package for YODL.

              Most  built-in  functions and macros expand the information they
              receive  the  way  they  receive  the  information.  I.e.,   the
              information   itself  is  only  evaluated  by  the  time  it  is
              eventually inserted into an  output  medium  (usually  a  file).
              However,  some builtin functions will evaluate their argument(s)
              once the argument is processed. They are:

       o      The ERROR() built-in function (see section [ERROR]);

       o      The EVAL() built-in function (see section [EVAL]);

       o      The FPUTS() built-in function (see section [FPUTS]);

       o      The   INTERNALINDEX()    built-in    function    (see    section
              [INTERNALINDEX]);

       o      The TYPEOUT() built-in function (see section [TYPEOUT]);

       o      The UPPERCASE() built-in function (see section [UPPERCASE]);

       o      The  WARNING()  built-in  function  (see section [WARNING]); All
              other built-in functions will not evaluate their arguments.  See
              the  mentioned  functions  for details, and in particular EVAL()
              for a description of this evaluation process.

       ADDTOCOUNTER
              The ADDTOCOUNTER function adds a given value to  a  counter.  It
              expects  two parameter lists: the counter name, and the value to
              add. The counter must be previously created with  DEFINECOUNTER.

              The  value  to  add can be negative; in that case, a value is of
              course subtracted from the counter.

              See further section [COUNTERS].

       ADDTOSYMBOL
              Since Yodl version 2.00 symbols can be manipulated. To add  text
              to  an  existing symbol the builtin ADDTOSYMBOL is available. It
              expects two parameter lists: the symbol’s name, and the text  to
              add  to  the  symbol.  The symbol must have been created earlier
              using DEFINECOUNTER (see section [DEFINECOUNTER]).  The  macro’s
              second argument is not evaluated while ADDTOSYMBOL is processed.
              Therefore, it is easy to add the text of another symbol  or  the
              expansion of a macro to a symbol value. E.g.,

                  ADDTOSYMBOL(one)(SYMBOLVALUE(two)XXnl())

              This will add the text of symbol two, followed by a new line, to
              the contents of symbol one only when symbol  one  is  evaluated,
              not when ADDTOSYMBOL is evaluated.

              Example:

                  ADDTOSYMBOL(LOCATION)(this is appended to LOCATION)

       ATEXIT ATEXIT  takes  one  parameter  list as argument. The text of the
              parameter list is appended to the output file.  Note  that  this
              text is subject to character table translations etc..

              An  example  using this function is the following. A document in
              the LaTeX typesetting language requires \end{document} to  occur
              at  the end of the document. To automatically append this string
              to the output file, the following specification can be used:

                  ATEXIT(NOEXPAND(\end{document}))

              Several ATEXIT lists can be defined. They are  appended  to  the
              output  file  in  the  reverse order of specification; i.e., the
              first ATEXIT list is appended to  the  output  file  last.  That
              means that in general the ATEXIT text should be specified when a
              ‘matching’ starting command is sent to the output file; as in:

                  COMMENT(Start the LaTeX document.)
                  NOEXPAND(\begin{document})

                  COMMENT(Ensure its proper ending.)
                  ATEXIT(NOEXPAND(\end{document}))

       CHAR   The command CHAR takes one argument, a number  or  a  character,
              and  outputs  its  corresponding  ASCII  character  to the final
              output file.  This command is built for ‘emergency  situations’,
              where  you  need to typeset a character despite the fact that it
              may  be  redefined  in  the  current  character  table  (for   a
              discussion  of  character  tables,  see [CHARTABLES]). Also, the
              CHAR function can be used to circumvent Yodl’s way  of  matching
              parentheses in a parameter list.

              The following arguments may be specified with CHAR (attempted in
              this order):

       o      A decimal number indicating the number of the character  in  the
              ascii-table (for example CHAR(41));

       o      A plain, single character  (for example CHAR(#)).

              So, when you’re sure that you want to send a printable character
              that is not a closing parenthesis to the output  file,  you  can
              use  the  form  CHAR(c), c being the character (as in, CHAR(;)).
              To send a non-printable character or a  closing  parenthesis  to
              the  output file, look up the ASCII number of the character, and
              supply that number as argument to the CHAR command.

              Example: The following two statements send an A  to  the  output
              file.

                  CHAR(65)
                  CHAR(A)

              The following statement sends a closing parenthesis:

                  CHAR(41)

              Another  way  to  send  a  string  to  the  output  file without
              expansion by character tables or by macro interpretation, is  by
              using  the function NOTRANS (see section [NOTRANS]). If you want
              to send a string to the output without macro interpretation, but
              with  character  table  translation,  use  NOEXPAND (see section
              [NOEXPAND]).

       CHDIR  The command CHDIR takes one argument, a directory to change  to.
              This  command  is  implemented  to  simplify  the  working  with
              includefile  (see   includefile   in   yodlmacros(7)).    As   a
              demonstration by example, consider the following fragment:

                  includefile(subdir/onefile)
                  includefile(subdir/anotherfile)
                  includefile(subdir/yetanotherfile)

              This fragment can be changed to:

                  CHDIR(subdir)
                  includefile(onefile)
                  includefile(anotherfile)
                  includefile(yetanotherfile)
                  CHDIR(..)

              The  current  directory,  as  given  to  CHDIR, only affects how
              includefile will search for its files.

              Note  that  this  example  assumes  that  the  current   working
              directory is a member of Yodl’s include-path specification (cf.,
              Yodl’s --include option).

       COMMENT
              The COMMENT function takes one parameter list. The text  in  the
              list is treated as comment. I.e., it is ignored. The text is not
              copied to the final output file.

       COUNTERVALUE
              COUNTERVALUE expands to the  value  of  a  counter.  Its  single
              parameter  list must contain the name of a counter.  The counter
              must have been created earlier using the builtin  DEFINECOUNTER.
              Example:

                  The counter has value COUNTERVALUE(MYCOUNTER).

              See also section [COUNTERS].

       DECWSLEVEL
              DECWSLEVEL  requires one (empty) parameter list.  It reduces the
              current white-space level. The white-space  level  typically  is
              used  in  files  that  only  define  Yodl macros. When no output
              should be generated while processing  these  files,  the  white-
              space  level  can  be used to check for this. If the white-space
              level exceeds zero, a warning will  be  generated  if  the  file
              produces  non-whitespace output. The builtin function DECWSLEVEL
              is used to reduce the whitespace level following a previous call
              of INCWSLEVEL.

              Once  the  white  space  level  exceeds  zero, no output will be
              generated. White space, therefore will effectively  be  ignored.
              The  white  space  level cannot be reduced to negative values. A
              warning is issued  if  that  would  have  happened  if  it  were
              allowed.

              Example:

                  INCWSLEVEL()
                  DEFINESYMBOL(....)
                  DEFINEMACRO(...)(...)(...)
                  DECWSLEVEL()

              Without   the   INCWSLEVEL  and  DECWSLEVEL,  calls,  the  above
              definition would generate four empty lines to the output stream.

              The  INCWSLEVEL  and  DECWSLEVEL  calls  may be nested. The best
              approach is to put an INCWSLEVEL at the first line of  a  macro-
              defining  Yodl-file,  and a matching DECWSLEVEL call at the very
              last line.

       DEFINECHARTABLE
              DEFINECHARTABLE is used to define a character translation table.
              The  function expects two parameterlists, containing the name of
              the character table and character table translations on separate
              lines. These character table  translations are of the form

                  character = quoted-string

              Here,  character  is always a value within single quotes. It may
              be a single character, an octal character value or a hexadecimal
              character  value.  The  single  character  may  be prefixed by a
              \-character (e.g., ’\\’). The octal character value  must  start
              with  a backslash, followed by three octal digits (e.g., ’\045’.
              The hexadecimal character value starts with 0x, followed by  two
              hexadecimal  characters.  E.g., ’0xbe’. The double quoted string
              may contain anything (but the  string  must  be  on  one  line),
              possibly containing escape-sequences too.

              Example:

                  DEFINECHARTABLE(demotable)(
                      ’&’     = "&"
                      ’\\’    = "\\backslash"
                      ’\045’  = "oct(45)"
                      ’0xa4’  = "hex(a4)"
                  )

              The  builtin  function  DEFINECHARTABLE  does  not  activate the
              table. The table is merely defined. To  activate  the  character
              translation table, use USECHARTABLE. The discussion of character
              tables is postponed to section [CHARTABLES].

       DEFINECOUNTER
              DEFINECOUNTER creates a new counter, to be subsequently used by,
              e.g,   the   USECOUNTER   function.  DEFINECOUNTER  expects  two
              parameter list: the  name  of  the  counter  to  create  and  an
              optional   initial   value.  By  default  the  counter  will  be
              initialized to zero.

              Examples:

                  DEFINECOUNTER(YEAR)(1950)
                  DEFINECOUNTER(NTIMES)()

              See also section [COUNTERS].

       DEFINEMACRO
              DEFINEMACRO is used to define new macros. This function requires
              three parameter lists:

       o      An  identifier,  being  the  name  of  the macro to define. This
              identifier  may  only  consist   of   uppercase   or   lowercase
              characters. Note that it can not contain numbers, nor underscore
              characters.

       o      A number, stating the number of arguments that  the  macro  will
              require once used. The number must be in the range 0 to 61.

       o      The text that the macro will expand to, once used. This text may
              contain the strings ARGx, x being 1, 2, etc..  At  these  places
              the  arguments  to the macro will be pasted in. The numbers that
              identify the arguments are 1 to 9, then A to Z and finally a  to
              z.  This  gives  a  range  of  61 expandable arguments, which is
              enough  for  all  real-life  applications.   For  example,   the
              following fragment defines a macro bookref, which can be used to
              typeset a reference to a book. It requires three arguments; say,
              an author, a title and the name of a publisher:

                  DEFINEMACRO(bookref)(3)(
                      Author(s):           ARG1
                      Book title:          ARG2
                      Published by:        ARG3
                  )

              Such a macro could be used as follows:

                  bookref(Sobotta/Becher)
                         (Atlas der Anatomie des Menschen)
                         (Urban und Schwarzenberg, Berlin, 1972)

              When called, it would produce the following output:

                      Author(s):           Sobotta/Becher
                      Book title:          Atlas der Anatomie des Menschen
                      Published by:        Urban und Schwarzenberg, Berlin, 1972

              While  applying a macro, the three parameter lists are pasted to
              the places where ARG1, ARG2 etc. occur in the definition.

              Note the following when defining new macros:

       o      The parameter  list  containing  the  name  of  the  new  macro,
              (bookref)   in   the  above  example,  must  occur  right  after
              DEFINEMACRO. No spaces are allowed in between. Space  characters
              and  newlines  may  however occur following this first parameter
              list.

              This behavior of the yodl program is similar to the usage of the
              defined   macro:   the  author  information  must,  enclosed  in
              parentheses,  follow  right  after  the  bookref  identifier.  I
              implemented  this  feature to improve the distinguishing between
              macros and real text. E.g., a macro me might be defined, but the
              text

                  I like me (but so do you)

              still  is  simple  text;  the  macro me only is activated when a
              parenthesis immediately follows it.

       o      Be careful when placing newlines or spaces in the definition  of
              a new macro. E.g., the definition, as given:

                  DEFINEMACRO(bookref)(3)(
                      Author(s):           ARG1
                      Book title:          ARG2
                      Published by:        ARG3
                  )

              introduces  extra  newlines  at  the beginning and ending of the
              macro, which will be copied to the output each time the macro is
              used.  The  extra  newline  occurs,  of course, right before the
              sequence Author(s): and following  the  evaluation  of  ARG3.  A
              simple  backslash  character  at the end of the DEFINEMACRO line
              would prevent the insertion of extra newline characters:

                  DEFINEMACRO(bookref)(3)(\
                      Author(s):           ARG1
                      Book title:          ARG2
                      Published by:        ARG3
                  )

       o      Note that when a macro is used which requires  no  arguments  at
              all,  one empty parameter list still must be specified. E.g., my
              macro package (see chapter [MACROPACKAGE]) defines  a  macro  it
              that  starts  a  bullet  item  in  a  list.  The  macro takes no
              arguments, but still must be typed as it().

              This  behavior  is  consistent:  it  helps   distinguish   which
              identifiers are macros and which are simple text.

       o      Macro  arguments  may  evaluate to text. When a \ is appended to
              the macro-argument, or in the default input  handling  within  a
              non-zero  white-space  level (see section [INCWSLEVEL]) this may
              invalidate a subsequent macro call. E.g., the macro

                  DEFINEMACRO(oops)(1)(
                      ARG1
                      XXnl()
                  )

              will, when called as oops(hello world), produce the output:

                  hello worldXXnl()

              To prevent this gluing to  arguments  to  subsequent  macros,  a
              single + should be prepended to the macro call:

                  DEFINEMACRO(oops)(1)(
                      ARG1
                      +XXnl()
                  )

              See also section [PLUSIDENT] obout the ‘+identifier’-sequence.

       o      Note  the preferred layout of macro definitions and macro calls.
              Adhere  to  this  form,  to  prevent  drowning   in   too   many
              parentheses. In particular:

       o      Put all elements of the macro definition on one line, except for
              the macro-expansion itself. Each expansion element should be  on
              a line by itself.

       o      When  calling  macros  put  the macro parameter lists underneath
              each other. If the macrolists  themselves  contain  macro-calls,
              put  each  call  again  on a line of its own, indenting one tab-
              position beyond the location of the opening parenthesis  of  the
              argument.

       o      No  continnuation  backslashes  are  required  between parameter
              lists. So, do not use them there to prevent unnecessary clutter.

       o      With  complex  calls,  indent  just  the  arguments, and put the
              parentheses in their required of logical locations.  Example  of
              a complex call:

                      complex(
                          first(
                              ARG1
                          )(
                              ARG2
                              +XXnl()
                          )
                          ARG3
                          +nop()
                          ARG4
                          +XXnl()
                      )

       o      Macro expansion proceeds as follows:

       o      The parameter lists are read from the input

       o      The   contents   of  the  parameters  then  replace  their  ARGx
              references in the macro’s definition (in some exceptional cases,
              clearly  indicated  as  such when applicable, the arguments will
              themselves  be  evaluated  first,  and  then   these   evaluated
              arguments  are used as replacements for their corresponding ARGx
              references).

       o      The now modified macro is read by Yodl’s lexical  scanner.  This
              may  result  in  yet another macro expansion, which will then be
              evaluated recursively.

       o      Eventually, all expansion is completed (well,  should  complete,
              since  Yodl  doesn’t test for eternal recursion) and scanning of
              the  input  continues  beyond  the  original  macro  call.   For
              example, assume we have the following two macros:

                  DEFINEMACRO(First)(1)(
                      Hello ARG1
                      +XXnl()
                  )
                  DEFINEMACRO(Second)(1)(
                      First(ARG1)
                      First(ARG1)
                  )

              and the following call is issued:

                  Second(Yodl)

              then the following will happen:

       o      Second(Yodl) is read as encountered.

       o      ARG1 in Second is replaced by YODL, and the resulting macro body
              is sent to the lexical scanner for evaluation: It will see:

                  First(Yodl)First(Yodl)

       o      The first call to First() is now evaluated. This will put (after
              replacing ARG1 by YODL) the following on the scanner’s input:

                  Hello Yodl+XXnl()First(Yodl)

       o      Hello  Yodl  contains  no  macro  call,  so it is written to the
              output stream. Remains:

                  +XXnl()First(Yodl)

       o      Assume XXnl() merely contains  a  newline  (represented  by  \n,
              here),  so  +XXnl()  is  now replaced by \n. This results in the
              following input for the lexical scanner:

                  \nFirst(Yodl)

       o      The \n is now written to the  output  stream,  and  the  scanner
              sees:

                  First(Yodl)

       o      The  second  call to First() is now evaluated. This will put the
              following on the scanner’s input:

                  Hello Yodl+XXnl()

       o      Hello Yodl is written to the output stream. Remains:

                  +XXnl()

       o      +XXnl() is now replaced by \n. The lexical scanner sees:

                  \n

       o      The newline is printed and we’re done.

       DEFINESYMBOL
              NOTE: this function has changed at the release of Yodl 2.00.  It
              now expects two parameter lists, rather than one

              DEFINESYMBOL  expects two arguments. An identifier, which is the
              name of the symbol to define,  and  the  textual  value  of  the
              symbol.  If the second argument is empty, the symbol is defined,
              but has an empty value.

              The earlier interpretation of a Yodl symbol as  a  logical  flag
              can  still  be  used,  but  allowing it to obtain textual values
              greatly simplifies various Yodl macros.

              Example:

                  DEFINESYMBOL(Yodl)(Your own document language)
                  DEFINESYMBOL(Options)()

       DELETECHARTABLE
              DELETECHARTABLE removes a definition of a character  table  that
              was  defined  by  DEFINECHARTABLE.  This  function  expects  one
              argument: the name of the character table remove.

              It’s an error to attempt to delete a  character  table  that  is
              currently  in  use  or  to  attempt  to  delete  a  non-existing
              character table.

              Example:

                  DELETECHARTABLE(mytable)

       DELETECOUNTER
              DELETECOUNTER removes a definition of a counter that was defined
              by  DEFINECOUNTER.  This function expects one argument: the name
              of the counter to remove.

              If the counter does not exist, a warning is issued.  It  is  not
              considered an error to try to delete a counter that has not been
              defined earlier.

              Example:

                  DELETECOUNTER(mycounter)

       DELETEMACRO
              DELETEMACRO removes a definition of a macro that was defined  by
              DEFINEMACRO. This function takes one argument: the macro name to
              remove.

              There is no error condition (except for syntax errors): when  no
              macro  with a matching name was previously defined, no action is
              taken.

              For example, the  safe  way  to  define  a  macro  is  by  first
              undefining  it.  This ensures that possible previous definitions
              are removed first:

              Example:
              DELETEMACRO(mymacro)

       DELETENOUSERMACRO
              DELETENOUSERMACRO  removes  a  ‘nousermacro’   definition.   The
              function  expects  one  argument:  the name of the ‘nousermacro’
              identifier to be removed from the nousermacro-set.

              There is no error condition (except for syntax errors): when the
              identifier  wasn’t stored as a ‘nousermacro’ no action is taken.

              Example:
              DELETENOUSERMACRO(mymacro)

       DELETESYMBOL
              DELETESYMBOL removes the definition of  a  symbol  variable.  It
              expects  one parameter list, holding the name of the variable to
              deleted.

              This macro has no error condition (except  for  syntax  errors):
              the  symbol  in  question may be previously defined, but that is
              not necessary.

              Example:

                  DELETESYMBOL(Options)

       DUMMY  This function is obsolete. It does nothing, and may  be  removed
              in future versions of Yodl.

       ENDDEF ENDDEF  is  obsolete,  and should be replaced by DECWSLEVEL.  It
              may be removed in future versions of Yodl.

       ERROR  The ERROR function takes one argument: text to  display  to  the
              standard  error  stream.  The current input file and line number
              are also displayed. After displaying the text, the yodl  program
              aborts with an exit status of 1.

              The  text  passed  to  the  function  is expanded first. See the
              example.

              The ERROR function is an example of a  function  that  evaluates
              its parameter list itself.

              This  command  can  be  used,  e.g.,  in a macro package when an
              incorrect macro is expanded. In my macro  package  (see  chapter
              [MACROPACKAGE])  the  ERROR function is used when the sectioning
              command chapter()  is  used  in  an  article  document  (in  the
              package, chapter’s are only available in books or reports).

              An  analogous  builtin  function is WARNING, which also prints a
              message but does not exit (see section [WARNING]).

              Example: In the following call, COUNTERVALUE(NTRIES) is replaced
              by its actual value:

                  ERROR(Stopping after COUNTERVALUE(NTRIES) attempts)

       EVAL   The  EVAL function takes one argument: the text to be evaluated.
              This function allows you to perform an  indirect  evaluation  of
              Yodl  commands.  Assume that there is a symbol varnam containing
              the name of a counter variable, then the following will  display
              the value of the counter, incrementing it first:

                  EVAL(NOTRANS(USECOUNTER)(SYMBOLVALUE(varnam)))

              The actions of the EVAL function can be described as follows:

       o      First,   the   NOTRANS(USECOUNTER)   is   evaluated,   producing
              USECOUNTER.

       o      Next, the open parentheses  is  processed,  producing  the  open
              parenthesis itself

       o      Then,  SYMBOLVALUE(varnam) is evaluated, producing the name of a
              counter, e.g. ‘counter’.

       o      Eventually the closing parentheis is  processed,  producing  the
              closing parenthesis itself.

       o      All this results in the text

                  USECOUNTER(counter)

       o      This  text is now presented to Yodl’s lexical scanner, resulting
              in incrementing the  counter,  and  displaying  its  incremented
              value.   It  should  be realized that macro arguments themselves
              are usually not evaluated. So, a construction like

                  USECOUNTER(EVAL(SYMBOLVALUE(varnam)))

              will fail, since EVAL(SYMBOLVALUE(varnam)) is not a  legal  name
              for  a  counter:  the  EVAL()  call is used here as an argument,
              which is not expanded. The distinction is subtle, and is  caused
              by   the   fact   that  builtin  functions  receive  unprocessed
              arguments, and may impose certain  requirements  on  them  (like
              USECOUNTER requiring the name of a counter).

              Summarizing: EVAL acts as follows:

       o      Its argument is presented to Yodl’s lexical scanner

       o      The  output  produced  by the processing of the argument is then
              inserted into the input stream in  lieu  of  the  original  EVAL
              call.

              Mosy  built-in  functions  will not evaluate their arguments. In
              fact, only ERROR, EVAL, FPUTS, INTERNALINDEX, TYPEOUT, UPPERCASE
              and WARNING() will evaluate their arguments.

              Postponing evaluations allows you to write:

                  DEFINESYMBOL(later)(SYMBOLVALUE(earlier))

              Eventually, and not when later is defined, a statement like

                  SYMBOLVALUE(later)

              will    produce   the   value   of   earlier   at   the   moment
              SYMBOLVALUE(later) is processed. This is,  in  all  its  complex
              consequences, what would be expected in most cases. It allows us
              to write general macros producing output that is only  evaluated
              when  the  text  of  symbols  and  values  of  arguments  become
              eventually, rather than when the macro is defined, available.

              Decisions like these invariably result in questions  like  ‘what
              if  I  have to keep original values in some situation?’ In those
              situations EVAL() must be used. The following example shows  the
              definition  of three symbols: one receives an initial value, two
              will return one’s actual value when two’s  value  is  displayed,
              three will, using EVAL(), store one’s initial value. The example
              also shows yet another way to suppress macro  calls. It uses the
              macro  nop()  which  is  defined  in the all standard conversion
              types.

                  DEFINESYMBOL(one)(This is one, before)
                  DEFINESYMBOL(two)(SYMBOLVALUE(one))
                  EVAL(DEFINESYMBOL+nop()(three)(SYMBOLVALUE(one)))
                  SETSYMBOL(one)(this is one, after)
                  SYMBOLVALUE(two)
                  SYMBOLVALUE(three)

       FILENAME
              The  function  FILENAME()  produces  an  absolute  path  to  the
              currently  processed  Yodl  file.  This  is  not necessarily the
              canonical path name, as it may contain current- and  parent-path
              directories.

       FPUTS  The  function  FPUTS expects two arguments: the first argment is
              information to be appended to a file, whose name is given as the
              second  argument. The first argument is processed by Yodl before
              it is appended to the requested  filename,  so  it  may  contain
              macro calls.

              For  example, the following statement will append a countervalue
              to the mentioned file:

                  FPUTS(There have been COUNTERVALUE(attempts) attempts)(/tmp/logfile)

              The second argument (name of the file) is not evaluated, but  is
              used as received.

       IFBUILTIN
              The  IFBUILTIN  function tests whether its first argument is the
              name of a builtin function. If so, the second parameter list  is
              evaluated,  else,  the  third  parameter  list is evaluated. All
              three parameter lists  (the  variable,  the  true-list  and  the
              false-list)  must  be  present;  though the true-list and/or the
              false-list may be empty parameter lists.

              Example:

                  IFBUILTIN(IFBUILTIN)(\
                      ‘BUILTIN’ is a builtin - function
                  )(\
                      ‘BUILTIN’ is NOT a builtin - function
                  )

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFCHARTABLE
              The IFCHARTABLE function tests whether its first argument is the
              name  of  a  character  table.  The character table needs not be
              active.  If the name is the  name  of  a  character  table,  the
              second  parameter  list  is evaluated, else, the third parameter
              list is evaluated. All three parameter lists (the name, the true
              list  and  the false list) must be present; though the true list
              and/or the false list may be empty parameter lists.

              Example:

                  IFCHARTABLE(standard)(\
                      ‘standard’ is a character tablebuiltin - function
                  )(\
                      ‘standard’ is NOT a character tablebuiltin - function
                  )

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFDEF  The IFDEF function  tests  for  the  definition  status  of  the
              argument in its first parameter list. If it is a defined entity,
              the  second  parameter  list  is  evaluated,  else,  the   third
              parameter  list  is  evaluated.  All  three parameter lists (the
              entity, the true list and  the  false  list)  must  be  present;
              though  the  true  list  and/or  the  false  list  may  be empty
              parameter lists.

              The true list is evaluated if the first argument is the name of:

       o      a built-in function, or

       o      a character table, or

       o      a counter, or

       o      a no-user-macro symbol, or

       o      a symbol, or

       o      a user-defined macro, or Example:

                  IFDEF(someName)(\
                      ‘someName’ is a defined entity
                  )(\
                      ‘someName is not defined.
                  )

              Please note the preferred layout: The first argument immediately
              follows the function name, then the second  argument  (the  true
              list)  is  indented,  as  is  the false list. The layout closely
              follows the preferred  layout  of  if-else  statements  of  many
              programming languages.

       IFEMPTY
              IFEMPTY  expects  three  arguments:  a symbol, a true-list and a
              false-list. IFEMPTY evaluates to the true-list if the symbol  is
              an empty string; otherwise, it evaluates to the false-list.

              The  function does not further evaluate its argument. Its use is
              primarily to test whether a macro has received  an  argument  or
              not. If the intent is to check whether a symbol’s value is empty
              or not, IFSTREQUAL [IFSTREQUAL] should be used, where the  first
              argument  is  the  name  of a symbol, and the second argument is
              empty.

              Example:

                  IFEMPTY(something)(\
                      ‘something’ is empty...
                  )(\
                      ‘something’ is not an empty string
                  )

              In the same way, IFEMPTY can be used to test whether an argument
              expands  to a non-empty string. A more elaborate example follows
              below. Say you  want  to  define  a  bookref  macro  to  typeset
              information  about  an  author,  a  book  title  and  about  the
              publisher. The publisher information may be  absent,  the  macro
              then typesets unknown:
              \
                  DEFINEMACRO(bookref)(3)(\
                      Author(s):      ARG1
                      Title:          ARG2
                      Published by:   \
                      IFEMPTY(ARG3)
                      (\
                          Unknown\
                      )(\
                          ARG3\
                      )
                  )

              Using the macro, as in:
              \
                  bookref(Helmut Leonhardt)
                         (Histologie, Zytologie und Microanatomie des Menschen)
                         ()

              would  now  result  in the text Unknown behind the Published by:
              line.

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFEQUAL
              IFEQUAL expects four argument lists. It tests whether its  first
              argument  is  equal  to  its  second  argument. If so, the third
              parameter list is evaluated, else, the fourth parameter list  is
              evaluated.  All  four argument lists must be present, though all
              can be empty lists.

              The first two arguments of IFEQUAL should be integral  numerical
              arguments. In order to determine whether the first two arguments
              are equal, their values are determined:

       o      If the argument starts with an integral  numerical  value,  that
              value is the value of the argument.

       o      If the argument is the name of a counter, the counter’s value is
              the value of the argument

       o      If the values of the  first  two  arguments  van  be  determined
              accordingly, their equality will determine whether the true list
              (when the values are equal) or the false list (when  the  values
              are unequal) will be evaluated.

       o      Otherwise, IFEQUAL will evaluate the false list.

              Example:

                  IFEQUAL(0)()(\
                      0 and an empty string are equal
                  )(\
                      0 and an empty string are not equal
                  )

              Please note the preferred layout: The first argument immediately
              follows the function name, then the second  argument  (the  true
              list)  is  indented,  as  is  the false list. The layout closely
              follows the preferred  layout  of  if-else  statements  of  many
              programming languages.

       IFGREATER
              IFGREATER  expects  four  argument  lists.  It tests whether its
              first argument is greater to its second  argument.  If  so,  the
              third  parameter  list  is evaluated, else, the fourth parameter
              list is evaluated. All four  argument  lists  must  be  present,
              though all can be empty lists.

              The   first  two  arguments  of  IFGREATER  should  be  integral
              numerical arguments. In order to determine whether the first two
              arguments are equal, their values are determined:

       o      If  the  argument  starts with an integral numerical value, that
              value is the value of the argument.

       o      If the argument is the name of a counter, the counter’s value is
              the value of the argument

       o      If  the  values  of  the  first  two arguments van be determined
              accordingly, their order relation  will  determine  whether  the
              true  list  (when  the  first  value  is greater than the second
              value) or the false list (when the first  value  is  smaller  or
              equal than the second value) will be evaluated.

       o      Otherwise, IFGREATER will evaluate the false list.

              Example:

                  IFGREATER(counter)(5)(\
                      counter exceeds the value 5
                  )(\
                      counter does not exceeds the value 5, or counter is no Yodl-counter.
                  )

              Please note the preferred layout: The first argument immediately
              follows the function name, then the second  argument  (the  true
              list)  is  indented,  as  is  the false list. The layout closely
              follows the preferred  layout  of  if-else  statements  of  many
              programming languages.

       IFMACRO
              The  IFMACRO  function  tests  whether its first argument is the
              name of a macro. If the name is the name of a macro, the  second
              parameter  list  is evaluated, else, the third parameter list is
              evaluated. All three parameter lists (the name,  the  true  list
              and the false list) must be present; though the true list and/or
              the false list may be empty parameter lists.

              Example:

                  IFMACRO(nested)(\
                      ‘nested’ is the name of a macro
                  )(\
                      There is no macro named ‘nested’
                  )

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFSMALLER
              IFSMALLER expects four argument  lists.  It  tests  whether  its
              first  argument  is  smaller  to its second argument. If so, the
              third parameter list is evaluated, else,  the  fourth  parameter
              list  is  evaluated.  All  four  argument lists must be present,
              though all can be empty lists.

              The  first  two  arguments  of  IFSMALLER  should  be   integral
              numerical arguments. In order to determine whether the first two
              arguments are equal, their values are determined:

       o      If the argument starts with an integral  numerical  value,  that
              value is the value of the argument.

       o      If the argument is the name of a counter, the counter’s value is
              the value of the argument

       o      If the values of the  first  two  arguments  van  be  determined
              accordingly,  their  order  relation  will determine whether the
              true list (when the first  value  is  smaller  than  the  second
              value)  or  the false list (when the first value is greater than
              or equal to the second value) will be evaluated.

       o      Otherwise, IFSMALLER will evaluate the false list.

              Example:

                  IFSMALLER(counter)(5)(\
                      counter is smaller than the value 5, or counter is no Yodl-counter
                  )(\
                      counter exceeds the value 5
                  )

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFSTREQUAL
              IFSTREQUAL tests for the equality of  two  strings.  It  expects
              four  arguments:  two  strings to match, a true list and a false
              list. The true list is only evaluated when the contents  of  the
              two string arguments exactly match.

              The first two arguments of IFSTREQUAL are partially evaluated:

       o      If  the  argument is the name of a symbol, the symbol’s value is
              the value of the argument

       o      Otherwise, the argument itself is used.

              In the degenerate case  where  the  string  to  be  compared  is
              actually  the  name of a SYMBOL, use a temporary SYMBOL variable
              containing the name of that symbol, and compare it  to  whatever
              you  want to compare it with. Alternatively, write a blank space
              behind the arguments, since the arguments are  then  interpreted
              ‘as  is’.  In practice, the need for these constructions seem to
              arise seldomly, however.

              Example:

                  IFSTREQUAL(MYSYMBOL)(Hello world)(
                      The symbol ‘MYSYMBOL’ holds the value ‘Hello world’
                  )(
                      The symbol ‘MYSYMBOL’ doesn’t hold the value ‘Hello world’
                  )

       IFSTRSUB
              IFSTRSUB tests whether a  string  is  a  sub-string  of  another
              string.  It acts similar to IFSTREQUAL, but it tests whether the
              second string is part of the first one.

              The first two arguments of IFSTREQULA are partially evaluated:

       o      If the argument is the name of a symbol, the symbol’s  value  is
              the value of the argument

       o      Otherwise, the argument itself is used.

              In  the  degenerate  case  where  the  string  to be compared is
              actually the name of a SYMBOL, use a temporary  SYMBOL  variable
              containing  the  name of that symbol, and compare it to whatever
              you want to compare it with. Alternatively, write a blank  space
              behind  the  arguments, since the arguments are then interpreted
              ‘as is’. In practice, the need for these constructions  seem  to
              arise seldomly, however.

              Example:

                      IFSTRSUB(haystack)(needle)(
                          ‘needle’ was found in ‘haystack’
                      )(
                          ‘needle’ was not found in ‘haystack’
                      )

              Note  that  both  ‘haystack’  and  ‘needle’  may be the names of
              symbols. If they are, their contents  are  is  compared,  rather
              than the literal names ‘haystack’ and ‘needle’

       IFSYMBOL
              The  IFSYMBOL  function  tests whether its first argument is the
              name of a symbol. If it is the name  of  a  symbol,  the  second
              parameter  list  is evaluated, else, the third parameter list is
              evaluated. All three parameter lists (the name,  the  true  list
              and the false list) must be present; though the true list and/or
              the false list may be empty parameter lists.

              Example:

                  IFSYMBOL(nested)(\
                      ‘nested’ is the name of a symbol
                  )(\
                      There is no symbol named ‘nested’
                  )

              Please note the preferred layout: The first argument immediately
              follows  the  function  name, then the second argument (the true
              list) is indented, as is the  false  list.  The  layout  closely
              follows  the  preferred  layout  of  if-else  statements of many
              programming languages.

       IFZERO IFZERO expects three parameter lists. The first argument defines
              whether  the  whole  function expands to the true list or to the
              false list.

              The first argument of IFZERO should  be  an  integral  numerical
              value. Its value is determined as follows:

       o      If  the  argument  starts with an integral numerical value, that
              value is the value of the argument.

       o      If the argument is the name of a counter, the counter’s value is
              the value of the argument

       o      Otherwise, IFZERO will evaluate the false list.

              Note that, starting with Yodl version 2.00 the first argument is
              not evaluated any further.  So,  COUNTERVALUE(somecounter)  will
              always be evaluated as 0. If the value of a counter is required,
              simply provide its name as the  first  argument  of  the  IFZERO
              function.

              Example:

                  DEFINEMACRO(environment)(2)(\
                      IFZERO(ARG2)(\
                          NOEXPAND(\end{ARG1})\
                      )(\
                          NOEXPAND(\begin{ARG1})\
                      )\
                  )

              Such a macro may be used as follows:

                  environment(center)(1)
                      Now comes centered text.
                  environment(center)(0)

              which  would  of  course  lead  to  \begin and \end{center}. The
              numeric second argument is used here as a on/off switch.

       INCLUDEFILE
              INCLUDEFILE  takes  one  argument,  a  filename.  The  file   is
              processed  by  Yodl.  If  a  file  should  be  inserted  without
              processing     the     builtin     function      NOEXPANDINCLUDE
              [NOEXPANDINCLUDE]  or  NOEXPANDPATHINCLUDE [NOEXPANDPATHINCLUDE]
              should be used.

              The yodl program supplies, when necessary, an extension  to  the
              filename.    The  supplied  extension  is  .yo,  unless  defined
              otherwise during the compilation of the program.

              Furthermore, Yodl tries to locate the file in the Yodl’s include
              path  (which  may be set using the --include option). The actual
              value of the include path is shown  in  the  usage  information,
              displayed when Yodl is started without arguments.

              Example:

                  INCLUDEFILE(latex)

              will  try to include the file latex or latex.yo from the current
              include parth. When the file is not found, Yodl aborts.

       INCLUDELIT, INCLUDELITERAL
              INCLUDELIT and  INCLUDELITERAL  are  obsolete.   NOEXPANDINCLUDE
              [NOEXPANDINCLUDE]  or  NOEXPANDPATHINCLUDE [NOEXPANDPATHINCLUDE]
              should be used instead.

       INCWSLEVEL
              INCWSLEVEL requires one (empty) parameter  list.   It  increases
              the  current  white-space level. The white-space level typically
              is used in files that only define Yodl macros.  When  no  output
              should  be  generated  while  processing these files, the white-
              space level can be used to check for this.  If  the  white-space
              level  exceeds  zero,  a  warning  will be generated if the file
              produces non-whitespace output. The builtin function  DECWSLEVEL
              is used to reduce the whitespace level following a previous call
              of INCWSLEVEL.

              Once the white space level  exceeds  zero,  no  output  will  be
              generated.  White  space, therefore will effectively be ignored.
              The white space level cannot be reduced to  negative  values.  A
              warning  is  issued  if  that  would  have  happened  if it were
              allowed.

              Example:

                  INCWSLEVEL()
                  DEFINESYMBOL(....)
                  DEFINEMACRO(...)(...)(...)
                  DECWSLEVEL()

              Without  the  INCWSLEVEL  and  DECWSLEVEL,  calls,   the   above
              definition would generate four empty lines to the output stream.

              The INCWSLEVEL and DECWSLEVEL calls  may  be  nested.  The  best
              approach  is  to put an INCWSLEVEL at the first line of a macro-
              defining Yodl-file, and a matching DECWSLEVEL call at  the  very
              last line.

       INTERNALINDEX
              INTERNALINDEX  expects  one  argument list. The argument list is
              evaluated and written to the index file.

              The index file is defined since Yodl version 2.00, and  contains
              the  fixup  information  which  was previously written to Yodl’s
              output as the .YODLTAGSTART.  ... .YODLTAGEND. sequence.

              The index file allows  for  greated  processing  speed,  at  the
              expense   of   an   additional  file.  The  associated  yodlpost
              postprocessing program will read and process the index file, and
              will fixup the corresponding yodl-output accordingly.

              The  index  file  is  not  created when output is written to the
              standard output name, since Yodl is unable to request the system
              for the current file offset.

              The   entries  of  the  index  file  always  fit  on  one  line.
              INTERNALINDEX will alter newline characters in its argument into
              single blank spaces. Each line starts with the current offset of
              Yodl’s output file, thus indicating the exact location  where  a
              fixup is requested. An example of a produced fixup line could be

                  3004 ref MACROPACKAGE

              indicating that at offset 3004 in the  produced  output  file  a
              reference  to  the  label  MACROPACKAGE is requested. Assuming a
              html  conversion,  The  postprocessor   will   thereupon   write
              something like

                  <a href="outfile04.html#MACROPACKAGE">4.3.2.</a>

              into the actual output file while processing Yodl’s output up to
              offset location 3004.

              Consequently, producing Yodl-output  normally  consists  of  two
              steps:

       o      First,  Yodl  itself  is  started, producing, e.g., out.idx (the
              index file) and out.yodl (Yodl’s raw output).

       o      Then, Yodl’s  post-processor  processes  out.idx  and  out.yodl,
              producing  one or more final output files, in which the elements
              of the index file have been properly handled. This may result in
              multiple   output   file,   like   report.html,   report01.html,
              report02.html etc.

       NEWCOUNTER
              NEWCOUNTER is obsolete. DEFINECOUNTER [DEFINECOUNTER] should  be
              used instead.

       NOEXPAND
              NOEXPAND  is  used to send text to the final output file without
              being expanded by Yodl (the other methods are  the  CHAR  macro,
              see   section   [CHAR],  and  the  NOTRANS  macro,  see  section
              [NOTRANS]).  NOEXPAND takes one  parameter  list,  the  text  in
              question.  Whatever  occurs  in  the  argument is not subject to
              parsing or expansion by Yodl, but is simply copied to the output
              file  (except  for  CHAR  functions  in  the argument, which are
              expanded. If  CHAR-expansion  is  not  required  either  NOTRANS
              [NOTRANS] can be used).

              Furthermore, the contents of the parameter list are also subject
              to character table  translations,  using  the  currently  active
              table.  This  should  come  as  no  surprise. Ignoring character
              tables would make both the processing  of  CHAR  calls  and  the
              NOTRANS function superfluous.

              So, the following situations are recognized:

              ----------------------------------------------
                                    support chartables
                                         and CHAR
                              ------------------------------
              Macro expansion   yes          no
              ----------------------------------------------
              Yes               (standard)   Push chartable
                                             (standard)
                                             Pop chartable
              No                NOEXPAND     NOTRANS
              ----------------------------------------------

              E.g.,  let’s  assume that you need to write in your document the
              following text:

                  INCLUDEFILE(something or the other)
                  IFDEF(onething)(
                      ...
                  )(
                      ....
                  )
                  NOEXPAND(whatever)

              The way to accomplish this is by prefixing the text by  NOEXPAND
              followed  by  an  open  parenthesis,  and  by postfixing it by a
              closing parenthesis.  Otherwise, the text would be  expanded  by
              Yodl while processing it (and would lead to syntax errors, since
              the text isn’t correct in the sence of the Yodl language).

              For this function, keep the following caveats in mind:

       o      There is only one thing that  a  NOEXPAND  cannot  protect  from
              expansion: an ARGx in a macro definition. The argument specifier
              is always processed. E.g., after

                  DEFINEMACRO(thatsit)(1)(
                      That is --> NOEXPAND(ARG1) <-- it!
                  )
                  thatsit(after all)

              the ARG1 inside the NOEXPAND statement is  replaced  with  after
              all.

       o      The  NOEXPAND  function must, as all functions, be followed by a
              parameter list. The parentheses of the list  must  therefore  be
              ‘balanced’.   For  unbalanced lists, use CHAR(40) to set an open
              parenthesis, or CHAR(41) to typeset a closing parenthesis.

       NOEXPANDINCLUDE
              NOEXPANDINCLUDE takes one argument,  a  filename.  The  file  is
              included.

              The  filename is uses ‘as is’. The include path is not used when
              locating this file.

              The argument to NOEXPANDINCLUDE is partially evaluated:

       o      If the argument is the name of a symbol, the symbol’s  value  is
              the value of the argument

       o      Otherwise,  the argument itself is used.  The thus obtained file
              name is not further evaluated: in particular,  it  will  not  be
              subject to character translations.

              The  contents of the file are included literally, not subject to
              macro expansion. Character translations are  performed,  though.
              If character translations are not appropriate, PUSHCHARTABLE can
              be used to suppress character table translations temporarily.

              The  purpose  of  NOEXPANDINCLUDE  is  to  include  source  code
              literally in the document, as in:

                  NOEXPANDINCLUDE(literal.c)

              The  function  NOEXPANDPATHINCLUDE  can be used to insert a file
              which is located in one of the directories specified  in  Yodl’s
              include path.

       NOEXPANDPATHINCLUDE
              NOEXPANDPATHINCLUDE  takes one argument, a filename. The file is
              included. The file is searched for in the directories  specified
              in Yodl’s includepath.

              The argument to NOEXPANDPATHINCLUDE is partially evaluated:

       o      If  the  argument is the name of a symbol, the symbol’s value is
              the value of the argument

       o      Otherwise, the argument itself is used.  The thus obtained  file
              name  is  not  further  evaluated: in particular, it will not be
              subject to character translations.

              Like the NOEXPANDINCLUDE function, the contents of the file  are
              included  literally,  not  subject to macro expansion. Character
              translations are performed, though.  If  character  translations
              are  not  appropriate, PUSHCHARTABLE [PUSHCHARTABLE] can be used
              to suppress character table translations temporarily.

              The purpose of NOEXPANDPATHINCLUDE is to include source code  as
              defined in a macro package literally into the document, as in:

                  NOEXPANDPATHINCLUDE(rug-menubegin.xml)

       NOTRANS
              NOTRANS  copies  its  one argument literally to the output file,
              without expanding macros  in  it  and  without  translating  the
              characters  with  the  current  translation  table.  The NOTRANS
              function is typically used  to  send  commands  for  the  output
              format to the output file.

              For example, consider the following code fragment:

                  COMMENT(--- Define character translations for \, { and } in LaTeX. ---)
                  DEFINECHARTABLE(standard)(
                      ’\\’    =    "$\\backslash$"
                      ’{’     =    "\\verb+{+"
                      ’}’     =    "\\verb+}+"
                  )

                  COMMENT(--- Activate the translation table. ---)
                  USECHARTABLE(standard)

                  COMMENT(--- Now two tests: ---)

                  NOEXPAND(\input{epsf.tex})
                  NOTRANS(\input{epsf.tex})

              NOEXPAND will send

                  $\backslash$input\verb+{+epsf.tex\verb+}+

              since  the  characters  in  its argument are translated with the
              standard translation  table.  In  contrast,  NOTRANS  will  send
              \input{epsf.tex}.

              The  parameter  list of NOTRANS must be balanced with respect to
              its parentheses. When using an unbalanced  set  of  parentheses,
              use CHAR(40) to send a literal (, or CHAR(41) to send a ).

              The   NOEXPAND   description   summarizes  all  combinations  of
              character translations and/or macro expansion, and how they  are
              handled and realized by Yodl.

       NOUSERMACRO
              NOUSERMACRO  controls yodl’s warnings in the following way: When
              Yodl is started with the -w  flag  on  the  command  line,  then
              warnings  are  generated  when  Yodl encounters a possible macro
              name, followed by a parameter list, without finding a  macro  by
              that  name.   Yodl  then  prints  something  like  cannot expand
              possible user macro.

              Examples of such sequences are, The  necessary  file(s)  are  in
              /usr/local/lib/yodl,  or  see  the  manual  page for sed(1). The
              candidate macros are file and sed; these  names  could  just  as
              well be ‘valid’ user macros followed by their parameter list.

              When  a  corresponding NOUSERMACRO statement appears before yodl
              encounters the candidate macros,  no  warning  is  generated.  A
              fragment might therefore be:

                  NOUSERMACRO(file sed)
                  The necessary file(s) are in ...
                  See the manual page for sed(1).

              The  NOUSERMACRO  accepts  one  or  more  names in its argument,
              separated by white space, commas, colons, or semi-colons.

       OUTBASE
              OUTBASE inserts the current basename of the output file into the
              output  file.  The basename is the name of the file of which the
              directory components and extension were stripped.

              If the output file is the standard output file, - is inserted.

       OUTDIR OUTDIR inserts the current path name of the output file into the
              output  file.  The  path  name  is  a, not necessarily absolute,
              designator of the directory in which the output file is located.
              If  the  output  file is indicated as, e.g., -o out, then OUTDIR
              simply inserts a dot.

              If the output file  is  the  standard  output  file,  a  dot  is
              inserted too.

       OUTFILENAME
              OUTFILENAME inserts the current filename of the output file into
              the output file. The filename is the name of the file  of  which
              the directory components  were stripped.

              If the output file is the standard output file, - is inserted.

       PARAGRAPH
              PARAGRAPH  isn’t really a builtin function, but as it is handled
              especially by Yodl, it is described here nonetheless.   Starting
              with Yodl 2.00  PARAGRAPH operates as follows:

              If  the  macro is not defined, new paragraphs, defined as series
              of consecutive empty lines written to the output stream, are not
              handled  different  from  any other series of characters sent to
              the output stream. I.e., they are inserted into that stream.

              However, if the macro  has  been  defined,  Yodl  will  call  it
              whenever  a  new  paragraph (defined as a series of at least two
              blank lines) was recognized.

              The empty lines that were actually recognized  may  be  obtained
              inside  the PARAGRAPH macro from the XXparagraph symbol, if this
              symbol has been be defined by that time.  If  defined,  it  will
              contain  the  white space that caused Yodl to call the PARAGRAPH
              macro.

              Note that, in order to inspect XXparagraph  it  must  have  been
              defined first. Yodl itself will not define this symbol itself.

              The  PARAGRAPH macro should be  defined as a macro not expecting
              arguments.  The macro is thus given  a  chance  to  process  the
              paragraph  in a way that’s fitting for the particular conversion
              type. If the PARAGRAPH macro  produces  series  of  empty  lines
              itself,  then  those empty lines will not cause Yodl to activate
              PARAGRAPH. So, Yodl itself will not recursively call  PARAGRAPH,
              although  the  macro  could  call itself recursively. Of course,
              such  recursive  activcation  of  PARAGRAPH  is  then  the  sole
              responsibility of the macro’s author, and not Yodl’s.

              Some  document  languages  do  not  need paragraph starts; e.g.,
              LaTeX handles its own paragraphs. Other  document  languages  do
              need it: typically, PARAGRAPH is then defined in a macro file to
              trigger some special action. E.g., a HTML converter might define
              a paragraph as:

                  DEFINEMACRO(PARAGRAPH)(0)(
                      XXnl()
                      NOTRANS(<p>)
                  )

              A  sytem  like xml has more strict requirements. Paragraphs here
              must be opened and closed using pairs of <p> and </p>  tags.  In
              those cases an auxiliary counter can be used to indicate whether
              there is an open paragraph or not.  The  PARAGRAPH  macro  could
              check  for  this  as  follows,  assuming  the  availability of a
              counter XXp:

                  DEFINEMACRO(PARAGRAPH)(0)(
                      XXnl()
                      IFZERO(XXp)(
                      )(
                          NOTRANS(</p>)
                      )
                      NOTRANS(<p>)
                      SETCOUNTER(XXp)(1)
                  )

              Note that  the  above  fragment  exemplifies  an  approach,  not
              necessarily  the  implementation  of  the PARAGRAPH macro for an
              xml-convertor.

       PIPETHROUGH
              The builtin function PIPETHROUGH is, besides SYSTEM, the  second
              function  with which a Yodl document can affect its environment.
              Therefore, the danger  of  ‘live  data’  exists  which  is  also
              described  in  the  section about SYSTEM (see section [SYSTEM]).
              Nevertheless, PIPETHROUGH can be very useful. It is intended  to
              use  external  programs to accomplish special features. The idea
              is that an external command is started, to which a block of text
              from within a Yodl document is ‘piped’. The output of that child
              program is piped back into the Yodl document; hence, a block  of
              text  is  ‘piped  through’  an  external  program.   Whatever is
              received again in the Yodl run, is further processed.

              The PIPETHROUGH function takes two arguments:

       o      the command to run, and

       o      the text to send to that command.

              Functionally, the occurrence of the PIPETHROUGH function and  of
              its  two  arguments  is  replaced  by whatever the child program
              produces on its standard output.

              An example might be the inclusion of the current date, as in:

              The current date is:
              PIPETHROUGH(date)()

              In this example the command is date and the text to send to that
              program is empty.

              The  main  purpose of this function is to provide a way by which
              external programs can be used to create, e.g., tables or figures
              for a given output format.  Further releases of Yodl may contain
              such dedicated programs for the output formats.

       POPCHARTABLE
              Character tables which are pushed onto  the  table  stack  using
              PUSHCHARTABLE()  are restored (popped) using POPCHARTABLE(). For
              a  description  of  this  mechanism  please  refer  to   section
              [PUSHINGTABLES].

       POPCOUNTER
              POPCOUNTER  is  used  to  remove  the  topmost  counter from the
              counter stack.  The values of counters may be pushed on a  stack
              using  PUSHCOUNTER  [PUSHCOUNTER]. To remove the topmost element
              of a counter’s stack POPCOUNTER is available. POPCOUNTER expects
              one  argument:  the  name  of the counter to pop. The previously
              pushed value then becomes  the  new  value  of  the  counter.  A
              counter’s  value may be popped after defining it, whereafter the
              stack will be empty, but the counter will still be  defined.  In
              that case, using the counter’s value is considered an error.

              Examples:

                  DEFINECOUNTER(YEAR)(1950)
                  POPCOUNTER(YEAR)
                  COMMENT(YEAR now has an undefined value)

              See also section [COUNTERS].

       POPMACRO
              POPMACRO   is  used  to  remove  the  actual  macro  definition,
              restoring a previously pushed definition.  The values of  macros
              may  be pushed on a stack using PUSHMACRO. To remove the topmost
              element of a  macro’s  stack  POPMACRO  is  available.  POPMACRO
              expects  one  argument:  the  name  of  the  macro  to  pop. The
              previously pushed value then becomes the new value of the macro.

              A  macro’s value may be popped after defining it, whereafter the
              stack will be empty, but the macro will  still  be  defined.  In
              that case, using the macro is considered an error.

              Example:

                  DEFINEMACRO(Hello)(1)(Hello, ARG1, this is a macro definition)
                  Hello(Karel)
                  PUSHMACRO(Hello)(1)(Hello, ARG1, this is the new definition)
                  Hello(Karel)
                  POPMACRO(Hello)
                  Hello(Karel)
                  COMMENT(The third activation of Hello() produces the same output
                          as the first activation)

       POPSYMBOL
              POPSYMBOL  is  used to remove the topmost symbol from the symbol
              stack.  The values of symbols may be pushed  on  a  stack  using
              PUSHSYMBOL  [PUSHSYMBOL].  To  remove  the  topmost element of a
              symbol’s stack POPSYMBOL is available.

              POPSYMBOL expects one argument: the name of the symbol  to  pop.
              The  previously  pushed  value then becomes the new value of the
              symbol. A symbol’s  value  may  be  popped  after  defining  it,
              whereafter the stack will be empty, but the symbol will still be
              defined. In that case, using the symbol’s value is considered an
              error.

              Example:

                  DEFINESYMBOL(YEAR)(This happened in 1950)
                  POPSYMBOL(YEAR)
                  COMMENT(YEAR now has an undefined value)

       POPWSLEVEL
              POPWSLEVEL  is  used  to  remove  the  topmost  wslevel from the
              wslevel stack.  The values of wslevels may be pushed on a  stack
              using  PUSHWSLEVEL  [PUSHWSLEVEL].  See  also section DECWSLEVEL
              [DECWSLEVEL]

              To remove the topmost element of a wslevel’s stack POPWSLEVEL is
              available.  POPWSLEVEL  expects  one  argument:  the name of the
              wslevel to pop. The previously pushed value then becomes the new
              value  of  the  wslevel.  A  wslevel’s value may be popped after
              defining it, whereafter the stack will be empty, but the wslevel
              will  still  be defined. In that case, using the wslevel’s value
              is considered an error.

              Example:

                  COMMENT(Assume WS level is zero)

                  PUSHWSLEVEL(1)
                  COMMENT(WS level now equals 1)

                  POPWSLEVEL()
                  COMMENT(WS level now equals 0 again)

       PUSHCHARTABLE
              Once a character table has been defined, it can be pushed onto a
              stack  using  PUSHCHARTABLE.  The pushed chartable may be popped
              later. PUSHCHARTABLE is described  in  more  detail  in  section
              [PUSHINGTABLES].

       PUSHCOUNTER
              PUSHCOUNTER  is  used  to  start another lifetime for a counter,
              pushing its current value on a stack. A stack is  available  for
              each individual counter.

              PUSHCOUNTER  expects  two  arguments: the name of the counter to
              push and its new value after pushing. When the  second  argument
              is  an empty parameter list, the new value will be zero. The new
              value may be specified as a numerical value, or as the  name  of
              an  existing  counter.  Specify the name of the counter twice to
              merely push its value, without modifying its current value.

              Examples:

                  DEFINECOUNTER(YEAR)(1950)
                  PUSHCOUNTER(YEAR)(1962)
                  COMMENT(YEAR now has the value 1962, and a pushed value of 1950)

              See also section [COUNTERS].

       PUSHMACRO
              PUSHMACRO is used to start another lifetime for a macro, pushing
              its current definition on a stack. A stack is available for each
              individual macro.

              PUSHMACRO expects three arguments: the  name  of  the  macro  to
              push,  the  number  of its arguments after pushing (which may be
              different from the number of arguments interpreted by the pushed
              macro)  and its new definition.

              So,  PUSHMACRO  is  used  exactly  like  DEFINEMACRO,  but  will
              redefine a current macro (or define a new macro if no macro  was
              defined by the name specified as its first argument.

              Example:

                  DEFINEMACRO(Hello)(1)(Hello, ARG1, this is a macro definition)
                  Hello(Karel)
                  PUSHMACRO(Hello)(1)(Hello, ARG1, this is the new definition)
                  Hello(Karel)
                  POPMACRO(Hello)
                  Hello(Karel)
                  COMMENT(The third activation of Hello() produces the same output
                          as the first activation)

       PUSHSYMBOL
              PUSHSYMBOL  is  used  to  start  another  lifetime for a symbol,
              pushing its current value on a stack. A stack is  available  for
              each individual symbol.

              PUSHSYMBOL expects two arguments: the name of the symbol to push
              and its new value after pushing. When the second argument is  an
              empty  parameter list, the new value will be zero. The new value
              may be specified as a numerical value, or  as  the  name  of  an
              existing  symbol. Specify the name of the symbol twice to merely
              push its value, without modifying its current value.

              Examples:

                  DEFINESYMBOL(YEAR)(This happened in 1950)
                  PUSHSYMBOL(YEAR)(This happended in 1962)
                  COMMENT(YEAR now has the value ‘This happended in 1962’ and a
                          pushed value of ‘This happened in 1950’)

       PUSHWSLEVEL
              PUSHWSLEVEL is used to start another lifetime of the white-space
              level  pushing  the  level’s  current value on a stack. See also
              section INCWSLEVEL [INCWSLEVEL]

              PUSHWSLEVEL expects one argument, the new value  of  the  white-
              space level. This value may be specified as a numerical value or
              as the name of a counter. The argument may be  empty,  in  which
              the new value will be zero.

              Example:

                  COMMENT(Assume WS level is zero)

                  PUSHWSLEVEL(1)
                  COMMENT(WS level now equals 1)

                  POPWSLEVEL()
                  COMMENT(WS level now equals 0 again)

       RENAMEMACRO
              RENAMEMACRO  takes  two  arguments: the name of a built-in macro
              (such as INCLUDEFILE) and its new name.

              E.g., after

                  RENAMEMACRO(INCLUDEFILE)(include)

              a file must be included by include(file).   INCLUDEFILE  can  no
              longer  be  used for this: following the RENAMEMACRO action, the
              old name can no longer be used; it becomes an undefined  symbol.

              If  you want to make an alias for a built-in command, do it with
              DEFINEMACRO. E.g., after:

                  DEFINEMACRO(include)(1)(INCLUDEFILE(ARG1))

              both INCLUDEFILE and include can be used to include a file.

       SETCOUNTER
              SETCOUNTER expects two parameter lists: the name of  a  counter,
              and a numeric value or the name of another counter.

              The corresponding counter (which must be previously created with
              NEWCOUNTER) is set to, respectively, the numeric  value  or  the
              value of the other counter.

              See also section [COUNTERS].

       SETSYMBOL
              SETSYMBOL expects two parameter lists: the name of a symbol, and
              the text to assign to the named symbol.

       STARTDEF
              STARTDEF is obsolete. Instead, INCWSLEVEL [INCWSLEVEL] should be
              used.

       SUBST  SUBST is a general-purpose substitution mechanism for strings in
              the input. SUBST takes two arguments:  a  search  string  and  a
              substitution string.  E.g., after

                  SUBST(VERSION)(1.00)

              YODL  will transorm all occurrences of VERSION in its input into
              1.00.

              SUBST  is  also  useful  in  situations  where   multi-character
              sequences  should  be  converted  to  accent characters. E.g., a
              LaTeX converter might define:

                  SUBST(’e)(NOTRANS(\’{e}))

              Each ’e in the input will then be converted to e.

              SUBST may be useed in combination with the command line flag -P,
              as in a invocation

                  yodl2html -P’SUBST(VERSION)(1.00)’ myfile.yo

              Another useful substitution might be:

                  SUBST(_OP_)(CHAR(40))
                  SUBST(_CP_)(CHAR(41))

              which  defines  an  opening  parenthesis  (_OP_)  and  a closing
              parenthesis (_CP_) as mapped to the CHAR function.  The  strings
              _OP_ and _CP_ might then be used to produce unbalanced parameter
              lists.

              Note that:

       o      The first argument of the SUBST command, the search  string,  is
              taken  literally.  Yodl  does  not expand it; the string must be
              literally matched in the input.

       o      The second argument, the replacement, is  further  processed  by
              Yodl.    Protect   this   text  by  NOTRANS  or  NOEXPAND  where
              appropriate.

              Substitutions occur extremely early  while  YODL  processes  its
              input  files.  In  order to processs its input files, YODL takes
              the following basic steps:

       1.     It requests input from its lexical scanner (so-called tokens)

       2.     Its parser processes the tokens produced by the lexical scanner

       3.     Its parser may send text  to  an  output  ‘object’,  which  will
              eventually  appear  in  the output file generated by YODL.  YODL
              will  perform  all  macro  substitutions  in  step  2,  and  all
              character  table  conversions  in  step  3. However, the lexical
              scanner has access to the SUBST  definitions:  as  soon  as  its
              lexical  analyzer  detects  a  series of characters matching the
              defining sequence of a SUBST definition, it  will  replace  that
              defining  sequence  by  its  definition. That definition is then
              again read by the lexical scanner. Of  course,  this  definition
              may,   in  turn,  contain  defining  sequences  of  other  SUBST
              definitions: these will then be replaced by their definitions as
              well. This implies:

       o      Circular  definitions may cause the lexical scanner to get stuck
              in a replacement loop. It is the responsibility  of  the  author
              defining  SUBST  definitions  to  make  sure  that  this doesn’t
              happen.

       o      Neither the parser, nor the output object ever  sees  the  SUBST
              defining   character   sequences:   they  will  only  see  their
              definitions.

       SYMBOLVALUE
              SYMBOLVALUE expands  to  the  value  of  a  symbol.  Its  single
              parameter  list  must  contain the name of a symbol.  The symbol
              must have been created earlier using the builtin DEFINESYMBOL.
              Example:

                  The symbol has value SYMBOLVALUE(MYSYMBOL).

       SYSTEM SYSTEM takes one argument: a command to execute. The command  is
              run  via  the  standard  C function system. The presence of this
              function in the Yodl language  introduces  the  danger  of  live
              data. Imagine someone sending you a document containing

                  SYSTEM(rm *)

              To  avoid  such  malevolent  side effects, YODL has a flag -l to
              define the ‘live data policy’. By default, -l0 is implied  which
              suppresses  the  SYSTEM  function  and  the  related PIPETHROUGH
              function. See also section [USING].

              Despite the potential danger, SYSTEM can be useful in many ways.
              E.g.,  you  might  want  to  log  when  someone  processes  your
              document, as in:

                  SYSTEM(echo Document processed! | mail myself@my.host)

              Note that SYSTEM merely performs an system-related task. It’s  a
              process  that  is separated from the YODL process itself. One of
              the consequences of this is that any output generated by  SYSTEM
              will  not normally appear into YODL’s output file. If the output
              of a subprocess should be  inserted  into  YODL’s  output  file,
              either use PIPETHROUGH [PIPETHROUGH], or insert a temporary file
              as shown in the following example:

                  SYSTEM(date > datefile)
                  The current date is:
                  INCLUDEFILE(datefile)
                  SYSTEM(rm datefile)

       TYPEOUT
              TYPEOUT requires one parameter list. The text  of  the  list  is
              sent  to  the standard error stream, followed by a newline. This
              feature can be handy to show, e.g.,  messages  such  as  version
              numbers in macro package files.

              Example:  The  following macro includes a file and writes to the
              screen that this file is currently processed.

                  DEFINEMACRO(includefile)(1)(
                      TYPEOUT(About to process document: ARG1)
                      INCLUDEFILE(ARG1)
                  )

       UNDEFINEMACRO
              UNDEFINEMACRO  is  deprecated.  Use  DELETEMACRO   [DELETEMACRO]
              instead.

       UPPERCASE
              UPPERCASE  converts  a  string or a part of it to upper case. It
              has two arguments:

       o      The string to convert;

       o      A length, indicating how  many  characters  (starting  from  the
              beginning  of  the  string)  should  be  converted.   The length
              indicator can be smaller than one or larger than the  length  of
              the string; in that case, the whole string is convertered.

              Example:

                  UPPERCASE(hello world)(1)
                  UPPERCASE(hello world)(5)
                  UPPERCASE(hello world)(0)

              This code sample expands to:

                  Hello world
                  HELLO world
                  HELLO WORLD

       USECHARTABLE
              USECHARTABLE takes one parameter list: the name of a translation
              table to activate. The table must previously have  been  defined
              using   DEFINECHARTABLE.   See   section   [CHARTABLES]   for  a
              description of character translation tables.

              Alternatively, the name may be empty in which case  the  default
              character mapping is restored.

       USECOUNTER
              USECOUNTER is a combination of ADDTOCOUNTER and COUNTERVALUE. It
              expects one parameter list: the name of an defined counter  (see
              DEFINECOUNTER [DEFINECOUNTER]).

              The counter is first incremented by 1. Then the function expands
              to the counter’s value.

              See also section [COUNTERS].

       VERBOSITY
              VERBOSITY expects two arguments, and may be used to  change  the
              verbosity  level  inside  YODL  files.  The function may be used
              profitably for debugging purposes, to debug the expansion  of  a
              macro or the processing of a YODL input file.

              The  first  argument  indicates the procesing mode of the second
              argument, and it may be:

       o      Empty, in which case the  message-level  is  set  to  the  value
              specified in the second argument;

       o      +,  in  which  case  the  value specified in the second argument
              augments the current message level;

       o      -, in which case the value  specified  in  the  second  argument
              augments is removed from the current message level

              The  second argument specifies one or more, separated by blanks,
              message level names or it may be  set  to  a  hexadecimal  value
              (starting  with  0x),  using  hexadecimal  values  to  represent
              message levels. Also, NONE may be used, to  specify  no  message
              level, or ALL can be used to specify all message levels.

              The following message levels are defined:

       o      ALERT  (0x40). When an alert-error occurs, Yodl terminates. Here
              Yodl requests something of the system (like  a  get_cwd()),  but
              the system fails.

       o      CRITICAL  (0x20). When a critical error occurs, Yodl terminates.
              The message itself can  be  suppressed,  but  exiting  can’t.  A
              critical condition is, e.g., the omission of an open parenthesis
              at a location where a parameter list should appear,  or  a  non-
              existing  file  in  an  INCLUDEFILE  specification (as this file
              should be parsed). A non-existing file  with  a  NOEXPANDINCLUDE
              specification is a plain (non-critical) error.

       o      DEBUG  (0x01).  Probably too much info, like getting information
              about each character that was read by Yodl.

       o      ERROR (0x10). An error  (like  doubly  defined  symbols).  Error
              messages will not stop the parsing of the input (up to a maximum
              number of errors), but no output is generated.

       o      INFO (0x02). Not as detailed as ‘debug’,  but  still  very  much
              info, like information about media switches.

       o      NOTICE  (0x04).  Information  about,  e.g., calls to the builtin
              function calls.

       o      WARNING (0x08). Something you should know  about,  but  probably
              not affecting Yodl’s proper functioning

              There   also  exists  a  level  EMERG  (0x80)  which  cannot  be
              suppressed.

              The value 0x00 represents NONE, the value 0xff represents ALL.

              When specifying multiple message levels  using  the  hexadecimal
              form,  their  hexadecimal  values should be binary-or-ed: adding
              them is ok, as long as you don’t specify ALL:

                  VERBOSITY()(0x06)
                  COMMENT(this specifies ‘INFO’ and ‘NOTICE’)

              When specifying message levels by their names, the names may  be
              truncated  at  a  unique point. However, the message level names
              are interpreted case sensitively, so INF for INFO is  recognized
              as  such,  but  info  for INFO isn’t. The following examples all
              specify verbosity levels INFO and NOTICE:

                  VERBOSITY()(I N)
                  VERBOSITY()(N I)
                  VERBOSITY()(NOT IN)
                  VERBOSITY()(INFO NOTICE)

       WARNING
              WARNING takes one argument: text to display as  a  warning.  The
              yodl  program  makes  sure  that  before  showing  the text, the
              current file and line  number  are  printed.  Other  than  this,
              WARNING works just as TYPEOUT (see section [TYPEOUT]).

              Note  that  an  analogous  function ERROR exists, which prints a
              message and then terminates the program (see section [ERROR]).

       WRITEOUT
              WRITEOUT is deprecated, use FPUTS [FPUTS] instead.

OPTIONS

       --

FILES

       The files in /usr/share/yodl define the converter’s macro packages. The
       scripts yodl2tex, yodl2html, yodl2man etc. perform the conversions.

SEE ALSO

       yodl(1), yodlmanpage(7), yodlconverters(1)

DIAGNOSTICS

       Error  messages  and warnings are printed to stderr. There are too many
       warnings or error messages to  enumerate,  but  they  should  be  self-
       explanatory.

BUGS

       --

AUTHOR

           Frank B. Brokken (f.b.brokken@rug.nl),