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December 21, 2015 09:59
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| # Given an expression, computes its "complexity". | |
| use strict; | |
| use warnings; | |
| use feature 'say'; | |
| use Data::Dumper; | |
| use Perlito5::Compiler; | |
| use Perlito5::Perl5::Emitter; | |
| use Perlito5::Perl5::PrettyPrinter; | |
| use Data::Dumper; | |
| use Perlito5::AST; | |
| use Perlito5::Dumper; | |
| $Perlito5::PKG_NAME = 'main'; | |
| $Perlito5::PROTO = {}; | |
| sub traverse_breadth_first { | |
| my ($ast, $callback) = @_; | |
| my @queue = ($ast); | |
| while (@queue) { | |
| my $node = shift @queue; | |
| if (exists $node->{arguments}) { | |
| push @queue, $_ for @{ $node->{arguments} }; | |
| } | |
| $callback->($node); | |
| } | |
| } | |
| sub lg { | |
| my $x = shift // die 'undef value in lg'; | |
| log($x) / log(2.0); | |
| } | |
| sub symbols { | |
| my $ast = shift; | |
| my @symbols; | |
| traverse_breadth_first($ast, sub { | |
| my ($node) = @_; | |
| if (ref $node eq 'Perlito5::AST::Apply') { | |
| push @symbols, $node->{code} | |
| } else { | |
| push @symbols, ref $node; | |
| } | |
| }); | |
| return @symbols; | |
| } | |
| sub entropy { | |
| my (@symbols) = @_; | |
| my %dist; | |
| my $inc = 1.0 / (scalar @symbols); | |
| for (@symbols) { | |
| $dist{$_} //= 0.0; | |
| $dist{$_} += $inc; | |
| } | |
| my $ret = 0.0; | |
| for (values %dist) { | |
| $ret += $_ * lg($_); | |
| } | |
| return -$ret; | |
| } | |
| sub get_ast { | |
| my $source = shift; | |
| my $statements = Perlito5::Grammar::exp_stmts($source, 0); | |
| my $ast = Perlito5::Match::flat($statements)->[0]; | |
| } | |
| sub compare_expressions { | |
| my (@strings) = @_; | |
| my @asts = map { get_ast($_) } @strings; | |
| my @entropies = map { entropy(symbols($_)) } @asts; | |
| my %rev_map; | |
| for (0..$#entropies) { | |
| my ($entropy, $string) = ($entropies[$_], $strings[$_]); | |
| $rev_map{$entropy} //= []; | |
| push @{ $rev_map{$entropy} }, $string; | |
| } | |
| my @ordered = sort keys %rev_map; | |
| say "Expressions ordered by complexity:"; | |
| for (1..@ordered) { | |
| my $e = join "\n\t ", @{ $rev_map{$ordered[$_-1]} }; | |
| say "\t$_: " . $e; | |
| } | |
| } | |
| @ARGV >= 2 || die 'Need at least two args'; | |
| compare_expressions(@ARGV); |
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