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Re: Parsing Boolean expressions

by tybalt89 (Prior)
on Apr 23, 2017 at 16:08 UTC ( #1188692=note: print w/replies, xml ) Need Help??


in reply to Parsing Boolean expressions

Lacking adequate specs :)

#!/usr/bin/perl # http://perlmonks.org/?node_id=1188650 # Parsing Boolean expressions use strict; use warnings; use Data::Dump 'pp'; my @tests = grep /\S/, split /\n/, <<END; Y = A + (B*C) Y = A + (B' + (C*D)') Y = A*(B*(C'+D)') Y = A # wire Y = (A')' # double negation Y = A' # NOT gate Y = (A + B)' # NOR gate Y = (A * B)' # NAND gate Y = (A' + B')' # AND gate by De Morgan Y = (A' * B')' # OR gate by De Morgan END for ( @tests ) # for each test case { print "\nparsing: $_\n"; for my $input (glob join '', map "$_:\{0,1\}", # for each combinatio +n sort s/.*=|#.*//gr =~ /\w+/g) # of input values { my %dictionary = $input =~ /(\w+):(0|1)/g; Parsing::Boolean::Expressions::parse( $_, \%dictionary ); pp \%dictionary; } } package Parsing::Boolean::Expressions; ######################## my $vars; # variable dictionary hash ref sub err { die s/\G/<* @_ *>/r, "\n" } sub closeparen { /\G\)/gc ? shift : err "missing )" } sub expr { my $p = shift; # precedence /\G(?:\s+|#.*)+/gc; # skip whitespace my $answer = /\G(\w+)\s*/gc ? do { my $name = $1; /\G=/gc ? $vars->{$name} = expr(0) : $vars->{$name} } : /\G\(/gc ? closeparen expr(0) : err "syntax error"; /\G(?:\s+|#.*)+/gc, # skip whitespace $p <= 3 && /\G'/gc ? $answer ^= 1 : # highest precedence $p <= 2 && /\G\*/gc ? $answer &= expr(3) : $p <= 1 && /\G\+/gc ? $answer |= expr(2) : # lowest precedence return $answer while 1; } sub parse # takes expression string and ref to dictionary hash { (local $_, $vars) = @_; expr(0); /\G\z/gc or err "incomplete parse"; } # end of package Parsing::Boolean::Expressions

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