Provided by: yodl_3.00.0-6ubuntu1_i386

#### 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.

NOTE: Starting with Yodl version 3.00.0 Yodl’s default  file  inclusion
behavior  has  changed. The current working directory no longer remains
fixed at the directory in  which  Yodl  is  called,  but  is  volatile,
changing to the directory in which a yodl-file is located. This has the
advantage that Yodl’s file inclusion behavior now matches the  way  C’s
#include  directive operates; it has the disadvantage that it may break
some current documents.  Conversion,  however  is  simple  but  can  be
avoided  altogether if Yodl’s -L (--legacy-include) option is used. The
builtins  INCLUDEFILE,  NOEXPANDINCLUDE  and  NOEXPANDPATHINCLUDE   are
affected by this new behavior.

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
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.

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].

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.,

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,

Example:

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, 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).

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  as  well:  in the double
quoted string the standard C escape  sequences  \a  (alert),  \b
(beep),  \f  (formfeed),  \n (newline), \r (carriage return), \t
(tab), and \v (vertical tab) are  recognized  and  automatically
converted  to  their special meanings. Starting with Yodl 2.14.0
octal  and  hexadecimal  constants  may  also  be  used.   E.g.,
character  Y may also be specified using the octal value \131 or
the hexadecimal value \x59.  Any  other  character  following  a
defines itself: \\ represents a single backslash character.

Example:

DEFINECHARTABLE(demotable)(
’&’     = "&amp;"
’\\’    = "\\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)()

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
)

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

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
)

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
)

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()
)

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(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

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
publisher.  The  publisher  information may be absent, the macro
then typesets unknown:
\
DEFINEMACRO(bookref)(3)(\
Author(s):      ARG1
Title:          ARG2
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.

NOTE: Starting with Yodl  version  3.00.0  Yodl’s  default  file
inclusion behavior has changed. The current working directory no
longer remains fixed at the directory in which Yodl  is  called,
but  is volatile, changing to the directory in which a yodl-file
is located. This has the advantage that  Yodl’s  file  inclusion
behavior now matches the way C’s #include directive operates; it
has the disadvantage that it may break some  current  documents.
Conversion,  however  is simple and can be avoided altogether if
Yodl’s -L (--legacy-include) option is used.

Example:

INCLUDEFILE(latex)

will try to include the file latex or latex.yo from the  current

INCLUDELIT, INCLUDELITERAL
INCLUDELIT  and  INCLUDELITERAL  are  obsolete.  NOEXPANDINCLUDE
[NOEXPANDINCLUDE] or  NOEXPANDPATHINCLUDE  [NOEXPANDPATHINCLUDE]

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

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 specified. The include path is not  used
when locating this file.

NOTE:  Starting  with  Yodl  version  3.00.0 Yodl’s default file
inclusion behavior has changed. The current working directory no
longer  remains  fixed at the directory in which Yodl is called,
but is volatile, changing to the directory in which a  yodl-file
is  located.  This  has the advantage that Yodl’s file inclusion
behavior now matches the way C’s #include directive operates; it
has  the  disadvantage that it may break some current documents.
Conversion, however is simple and can be avoided  altogether  if
Yodl’s -L (--legacy-include) option is used.

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.

NOTE: Starting with Yodl  version  3.00.0  Yodl’s  default  file
inclusion behavior has changed. The current working directory no
longer remains fixed at the directory in which Yodl  is  called,
but  is volatile, changing to the directory in which a yodl-file
is located. This has the advantage that  Yodl’s  file  inclusion
behavior now matches the way C’s #include directive operates; it
has the disadvantage that it may break some  current  documents.
Conversion,  however  is simple and can be avoided altogether if
Yodl’s -L (--legacy-include) option is used.

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:

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)

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)

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
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.

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

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)(
INCLUDEFILE(ARG1)
)

UNDEFINEMACRO
UNDEFINEMACRO   is  deprecated.  Use  DELETEMACRO  [DELETEMACRO]

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.

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:

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

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
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.



#### FILES

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



#### SEEALSO

       yodlstriproff(1),    yodl(1),     yodlconverters(1),     yodlletter(7),
yodlmacros(7), yodlmanpage(7), yodlpost(1), yodlverbinsert(1).



#### BUGS

       --



#### AUTHOR

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