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|
#! /usr/local/bin/perl -sw
# DELETABLE PRODUCTIONS
use Parse::RecDescent;
$grammar =
q{
commands : command(s)
command : directive
| evaluation
directive: 'only prefix'
{ $thisparser->{deleted} = {infix=>1,postfix=>1} }
| 'not prefix'
{ $thisparser->{deleted}{prefix} = 1 }
evaluation: <reject: $thisparser->{deleted}{prefix}> op var var
{ print "prefix $item[3] $item[2] $item[4]\n" }
| <reject: $thisparser->{deleted}{infix}> var op var
{ print "infix $item[2] $item[3] $item[4]\n" }
| <reject: $thisparser->{deleted}{postfix}> var var op
{ print "postfix $item[2] $item[4] $item[3]\n" }
op : '+' | '-'
var : /(?!\d)\w+/
};
$parse = new Parse::RecDescent ($grammar);
while (<DATA>)
{
$parse->commands($_);
}
__DATA__
a + b
+ a b
a b +
not prefix
a + b
+ a b
a b +
only prefix
a + b
+ a b
a b +
not prefix
a + b
+ a b
a b +
|
