NAME

       xyacc - SPP modified yacc compiler compiler [IRAF]

SYNOPSIS

       xyacc [options] file

OPTIONS

       -b file_prefix
              Specify a file_prefix for output files

       -d     Also produce a header file y.tab.h.

       -l     Don't generate '#line' directives

       -P parser
              Specify parser file (default boot$xyacc/yaccpar.x)

       -Q(y/n)
              Flag  for version stamping. The -Qy option puts the version stamping information in
              y.tab.c. This allows you to know what version of  yacc  built  the  file.  The  -Qn
              option (the default) writes no version information.

       -t     Compiles runtime debugging code by default.

       -v     Prepares  the file y.output, which contains a description of the parsing tables and
              a report on conflicts generated by ambiguities in the grammar.

       -V     Output version information and exit

       -Y dir Specify location of yaccpar.x (default boot$xyacc).

DESCRIPTION

       The yacc command converts a context-free grammar  into  a  set  of  tables  for  a  simple
       automaton  that  executes  an  LALR(1)  parsing  algorithm.  The grammar can be ambiguous.
       Specified precedence rules are used to break ambiguities.

       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.

       Input files should follow the yacc convention of ending in .y.

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.