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.