#!/usr/bin/perl -w
use strict;
use Data::Dumper;
use Parse::Eyapp;
my $translationscheme = q{
%{
# head code is available at tree construction time
use Data::Dumper;
%}
%metatree
%left '-' '+'
%left '*'
%left NEG
%%
line: %name EXP
$exp { $lhs->{n} = $exp->{n} }
;
exp:
%name PLUS
exp.left '+' exp.right
{ $lhs->{n} .= $left->{n} + $right->{n} }
| %name TIMES
exp.left '*' exp.right
{ $lhs->{n} = $left->{n} * $right->{n} }
| %name NUM $NUM
{ $lhs->{n} = $NUM->{attr} }
| '(' $exp ')' %begin { $exp }
| exp.left '-' exp.right
{ $lhs->{n} = $left->{n} - $right->{n} }
| '-' $exp %prec NEG
{ $lhs->{n} = -$exp->{n} }
;
%%
# tail code is available at tree construction time
sub _Error {
exists $_[0]->YYData->{ERRMSG}
and do {
print $_[0]->YYData->{ERRMSG};
delete $_[0]->YYData->{ERRMSG};
return;
};
print "Syntax error.\n";
}
sub _Lexer {
my($parser)=shift;
$parser->YYData->{INPUT}
or return('',undef);
$parser->YYData->{INPUT}=~s/^\s*//;
for ($parser->YYData->{INPUT}) {
s/^([0-9]+(?:\.[0-9]+)?)//
and return('NUM',$1);
s/^([A-Za-z][A-Za-z0-9_]*)//
and return('VAR',$1);
s/^(.)//
and return($1,$1);
s/^\s*//;
}
}
sub Run {
my($self)=shift;
return $self->YYParse( yylex => \&_Lexer, yyerror => \&_Error );
}
}; # end translation scheme
$Data::Dumper::Indent = 1;
$Data::Dumper::Terse = 1;
$Data::Dumper::Deepcopy = 1;
Parse::Eyapp->new_grammar(
input=>$translationscheme,
classname=>'main',
firstline => 7,
outputfile => 'main.pm');
my $parser = main->new();
$parser->YYData->{INPUT} = "2+(3)";
my $t = $parser->Run() or die "Syntax Error analyzing input";
$t->translation_scheme;
print "$t->{n}\n";
print Dumper($t);