eyapp - A Perl front-end to the Parse::Eyapp module
eyapp [options] grammar[.eyp] eyapp -V eyapp -h grammar The grammar file. If no suffix is given, and the file does not exists, .eyp is added
The eyapp compiler is a front-end to the Parse::Eyapp module, which lets you compile Parse::Eyapp grammar input files into Perl LALR(1) Object Oriented parser modules.
Creates a file grammar.output describing your parser. It will show you a summary of conflicts, rules, the DFA (Deterministic Finite Automaton) states and overall usage of the parser.
Implies option -N. To produce a more detailed description of the states, the LALR tables aren't compacted. Use the combination -vN to produce an .output file corresponding to the compacted tables.
-N
-vN
.output
Create a standalone module in which the parsing driver is included. The modules including the LALR driver (Parse::Eyapp::Driver), those for AST manipulations (Parse::Eyapp::Node and Parse::Eyapp::YATW)) and Parse::Eyapp::Base are included - almost verbatim - inside the generated module.
Note that if you have more than one parser module called from a program, to have it standalone, you need this option only for one of your grammars;
Disable source file line numbering embedded in your parser module. I don't know why one should need it, but it's there.
Gives your parser module the package name (or name space or module name or class name or whatever-you-call-it) of module. It defaults to grammar
The compiled output file will be named outfile for your parser module. It defaults to grammar.pm or, if you specified the option -m A::Module::Name (see below), to Name.pm.
Produces as output (STDOUT) the grammar without the actions. Only the syntactic parts are displayed. Comments will be also stripped if the -v option is added.
-v
The -t filename option allows you to specify a file which should be used as template for generating the parser output. The default is to use the internal template defined in Parse::Eyapp::Output.pm. For how to write your own template and which substitutions are available, have a look to the module Parse::Eyapp::Output.pm : it should be obvious.
If you work on systems that understand so called shebangs, and your generated parser is directly an executable script, you can specify one with the -b option, ie:
eyapp -b '/usr/local/bin/perl -w' -o myscript.pl myscript.yp
This will output a file called myscript.pl whose very first line is:
#!/usr/local/bin/perl -w
The argument is mandatory, but if you specify an empty string, the value of $Config{perlpath} will be used instead.
Adds a modulino call '__PACKAGE->main(<prompt>) unless caller();' as the very last line of the output file. The argument is mandatory.
An abbreviation for the combined use of -b '' and -B ''
Equivalent to %tree.
%tree
Equivalent to the directive %nocompact. Do not compact LALR action tables.
%nocompact
Do not provide a default lexical analyzer. By default eyapp builds a lexical analyzer from your %token = /regexp/ definitions
eyapp
%token = /regexp/
The input grammar file. If no suffix is given, and the file does not exists, an attempt to open the file with a suffix of .eyp is tried before exiting.
Display current version of Parse::Eyapp and gracefully exits.
Display the usage screen.
The following eyapp program translates an infix expression like 2+3*4 to postfix: 2 3 4 * +
2+3*4
2 3 4 * +
%token NUM = /([0-9]+(?:\.[0-9]+)?)/ %token VAR = /([A-Za-z][A-Za-z0-9_]*)/ %right '=' %left '-' '+' %left '*' '/' %left NEG %defaultaction { "$left $right $op"; } %% line: $exp { print "$exp\n" } ; exp: $NUM { $NUM } | $VAR { $VAR } | VAR.left '='.op exp.right | exp.left '+'.op exp.right | exp.left '-'.op exp.right | exp.left '*'.op exp.right | exp.left '/'.op exp.right | '-' $exp %prec NEG { "$exp NEG" } | '(' $exp ')' { $exp } ; %%
Notice that there is no need to write lexer and error report subroutines. First, we compile the grammar:
pl@nereida:~/LEyapp/examples/eyappintro$ eyapp -o postfix.pl -C Postfix.eyp
If we use the -C option and no main() was written one default main sub is provided. We can now execute the resulting program:
-C
main()
main
pl@nereida:~/LEyapp/examples/eyappintro$ ./postfix.pl -c 'a = 2*3 +b' a 2 3 * b + =
When a non conformant input is given, it produces an accurate error message:
pl@nereida:~/LEyapp/examples/eyappintro$ ./postfix.pl -c 'a = 2**3 +b' Syntax error near '*'. Expected one of these terminals: '-' 'NUM' 'VAR' '(' There were 1 errors during parsing
Casiano Rodriguez-Leon
(c) Copyright 2006 Casiano Rodriguez-Leon
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.
Parse::Eyapp,
perldoc vgg,
The tutorial Parsing Strings and Trees with Parse::Eyapp (An Introduction to Compiler Construction in seven pages)> in
Parse::Eyapp
The pdf file in http://nereida.deioc.ull.es/~pl/perlexamples/Eyapp.pdf
http://nereida.deioc.ull.es/~pl/perlexamples/section_eyappts.html (Spanish),
eyapp,
treereg,
Parse::yapp,
yacc(1),
bison(1),
the classic book "Compilers: Principles, Techniques, and Tools" by Alfred V. Aho, Ravi Sethi and
Jeffrey D. Ullman (Addison-Wesley 1986)
Parse::RecDescent.
To install Parse::Eyapp, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Parse::Eyapp
CPAN shell
perl -MCPAN -e shell install Parse::Eyapp
For more information on module installation, please visit the detailed CPAN module installation guide.