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77 lines
1.5 KiB
JavaScript

"use strict";
let visitor = require("./visitor");
// AST utilities.
let asts = {
findRule(ast, name) {
for (let i = 0; i < ast.rules.length; i++) {
if (ast.rules[i].name === name) {
return ast.rules[i];
}
}
return undefined;
},
indexOfRule(ast, name) {
for (let i = 0; i < ast.rules.length; i++) {
if (ast.rules[i].name === name) {
return i;
}
}
return -1;
},
alwaysConsumesOnSuccess(ast, node) {
function consumesTrue() { return true; }
function consumesFalse() { return false; }
function consumesExpression(node) {
return consumes(node.expression);
}
let consumes = visitor.build({
rule: consumesExpression,
named: consumesExpression,
choice(node) {
return node.alternatives.every(consumes);
},
action: consumesExpression,
sequence(node) {
return node.elements.some(consumes);
},
labeled: consumesExpression,
text: consumesExpression,
simple_and: consumesFalse,
simple_not: consumesFalse,
optional: consumesFalse,
zero_or_more: consumesFalse,
one_or_more: consumesExpression,
group: consumesExpression,
semantic_and: consumesFalse,
semantic_not: consumesFalse,
rule_ref(node) {
return consumes(asts.findRule(ast, node.name));
},
literal(node) {
return node.value !== "";
},
class: consumesTrue,
any: consumesTrue
});
return consumes(node);
}
};
module.exports = asts;