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@rns
Created May 18, 2016 11:03
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ECMAScript::AST traversal example
# 1: Program
# 2: Statement
# 3: VariableStatement
# 3: VAR: 'var' @0:3
# 3: IDENTIFIER: 'i' @4:5
# 3: ASSIGN: '=' @6:7
# 3: DECIMALLITERAL: '0' @8:9
# 2: Statement
# 3: ExpressionStatement
# 3: IDENTIFIER: 'i' @11:12
# 3: ASSIGN: '=' @13:14
# 3: IDENTIFIER: 'i' @15:16
# 3: PLUS: '+' @17:18
# 3: DECIMALLITERAL: '1' @19:20
#!/usr/bin/env perl
use 5.010;
use strict;
use warnings FATAL => 'all';
use MarpaX::Languages::ECMAScript::AST;
use Data::Dumper;
$Data::Dumper::Deepcopy = 1;
$Data::Dumper::Indent = 0;
$Data::Dumper::Terse = 1;
$Data::Dumper::Sortkeys = 1;
my $ecmaSourceCode = 'var i = 0; i = i + 1;';
my $ecmaAstObject = MarpaX::Languages::ECMAScript::AST->new();
my $ast = $ecmaAstObject->parse($ecmaSourceCode);
my %semantic = map{ $_ => 1 } qw{
Program Statement VariableStatement ExpressionStatement
VAR IDENTIFIER ASSIGN DECIMALLITERAL PLUS
};
sub traverse{
my ($node) = @_;
state $level = 0;
# unpack node
my ($lhs, $rhs, $values) = map { $node->{$_} } qw { lhs rhs values };
# print debug info: uncomment to see what you may need to distill
# say "$level:", ' ' x $level, Dumper $node;
$level++ if $semantic{$lhs};
# process node based on its LHS -- node id -- unless it's just syntax
say qq{# $level:}, ' ' x $level, $lhs
if $semantic{$lhs}; # skip syntactic nodes
# process node RHS -- node children
for my $i (0..@$values-1){
# name & value -- node child
my $name = $rhs->[$i];
my $value = $values->[$i];
# process child as literal
if (ref $value eq "ARRAY"){
my ($start, $length, $literal) = @$value;
if (exists $semantic{$name}){
say qq{# $level:}, ' ' x $level, qq{$name: '$literal'}, ' @', $start, ':', $start + $length;
}
}
# process child recursively
elsif (ref $value eq "HASH"){
traverse($value);
$level--
if $semantic{$lhs}; # skip syntactic nodes
}
}
}
traverse($ast);
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rns commented May 18, 2016

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