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Re: Parsing Boolean expressions

by choroba (Bishop)
on Apr 23, 2017 at 21:13 UTC ( #1188721=note: print w/replies, xml ) Need Help??


in reply to Parsing Boolean expressions

I like Marpa::R2 for building grammars:
#!/usr/bin/perl use warnings; use strict; use feature qw{ say }; use Marpa::R2; my $dsl = << '__DSL__'; lexeme default = latm => 1 Assignment ::= var ('=') Expression action => ASSIGN Expression ::= var action => VAR | ('(') Expression (')') action => ::first assoc +=> group || Expression (q) action => NOT || Expression ('*') Expression action => AND || Expression ('+') Expression action => OR q ~ ['] var ~ [A-Z]+ :discard ~ whitespace whitespace ~ [\s]+ __DSL__ my %var; sub ASSIGN { $var{ $_[1] } = 0 + $_[2] } sub NOT { ! $_[1] } sub AND { $_[1] && $_[2] } sub OR { $_[1] || $_[2] } sub VAR { $var{ $_[1] } } my @input = ('Y = A + (B*C)', "Y = A + (B' + (C*D)')", "Y = A*(B*(C'+D)')"); my $grammar = 'Marpa::R2::Scanless::G'->new({ source => \$dsl }); for my $line (@input) { %var = map +( $_ => int rand 2 ), 'A' .. 'D'; my $result = $grammar->parse(\$line, { semantics_package => 'main' + }); say join ' ', %var; }
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord }map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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