XYACC(1)

NAME
xyacc - SPP modified yacc compiler compiler [IRAF]

SYNOPSIS
xyacc [options] file

DESCRIPTION
This is a version of yacc that has been modified to produce SPP language parsers. For the most part, it should follow the operation of standard yacc, with the differences noted below. See the man page for yacc for options.

DIFFERENCES

(1) The Yacc input syntax is unmodified, except that the comment convention is now as in SPP, rather than C (i.e., use #, rather than /*..*/). All defines, actions, etc. are of course given in the SPP language.

(2) The Yacc output file is "ytab.x", rather than "y.tab.c". The token defs file "y.tab.h" now contains SPP defines, rather than C #defines. The states file "y.output" is completely unmodified.

(3) The global declarations section %{ .. %} had to be changed somewhat because SPP does not have global variables. The section is now divided into two subsections. The first is for global defines, includes, etc. which go into the header area of the ytab.x file. Then follows a %L, telling Yacc that the local declarations for the parser procedure follow. This second section should contain variable and function declarations required for the user supplied actions (code fragments to be executed when a rule of the grammar is recognized) in the yyparse procedure.

(4) The global declarations section MUST contain the following two defines:
    YYMAXDEPTH   Depth of the parser stacks; determines
                 the maximum complexity of a language
                 construct which can be parsed.  A
                 typical value is 150.
    YYOPLEN      The length, in struct units, of a token
                 operand value structure.  You define the
                 operand structure to be whatever you wish;
                 all the parser needs to know is how big an
                 element is.  The lexical analyzer and the
                 actions, both of which are supplied by the
                 user, use the operand structure for
                 communications.  Operand structures are
                 always referred to by a Mem pointer.

SEE ALSO
yacc(1), xpp(1), rpp(1).

AUTHOR
This manual page was written by Zed Pobre <zed@debian.org>, for the Debian GNU/Linux system (but may be used by others). It includes text from the README file for xyacc in the IRAF sources.