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.