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.