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62 lines
1.4 KiB
JavaScript

var arrays = require("../utils/arrays"),
visitor = require("./visitor");
/* AST utilities. */
var asts = {
findRule: function(ast, name) {
return arrays.find(ast.rules, function(r) { return r.name === name; });
},
indexOfRule: function(ast, name) {
return arrays.indexOf(ast.rules, function(r) { return r.name === name; });
},
matchesEmpty: function(ast, node) {
function matchesTrue() { return true; }
function matchesFalse() { return false; }
function matchesExpression(node) {
return matches(node.expression);
}
var matches = visitor.build({
rule: matchesExpression,
choice: function(node) {
return arrays.some(node.alternatives, matches);
},
action: matchesExpression,
sequence: function(node) {
return arrays.every(node.elements, matches);
},
labeled: matchesExpression,
text: matchesExpression,
simple_and: matchesTrue,
simple_not: matchesTrue,
optional: matchesTrue,
zero_or_more: matchesTrue,
one_or_more: matchesExpression,
semantic_and: matchesTrue,
semantic_not: matchesTrue,
rule_ref: function(node) {
return matches(asts.findRule(ast, node.name));
},
literal: function(node) {
return node.value === "";
},
"class": matchesFalse,
any: matchesFalse
});
return matches(node);
}
};
module.exports = asts;