Ubuntu Manpage: yodlbuiltins - Builtins for the Yodl converters

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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 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,
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 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)()

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:

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
)

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.
)

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.

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
)

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.
)

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’
)

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
)

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.

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’
)

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 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.

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

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 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:

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()
)

A system like xml has more strict requirements. Paragraphs here must be opened and closed using
pairs of and 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()
)
NOTRANS()
SETCOUNTER(XXp)(1)
)

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

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 redefines a current macro (or define a new
macro if no macro was defined by the name specified as its first argument.

Example:

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.

FILES

       The files in tmp/wip/macros define the converter’s  macro  packages.  The  scripts  yodl2tex,  yodl2html,
       yodl2man etc. perform the conversions.

BUGS

--

AUTHOR

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

NAME

SYNOPSIS

DESCRIPTION

FILES

SEE ALSO

BUGS

AUTHOR