@fauton/cfg/dist/generateParseTreeFromDerivations.js

A package to work with context free grammars and LL1 parsers

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.generateParseTreeFromDerivations = void 0;
/**
 * Generate parse tree from derivations
 * @param variables Array of variables string
 * @param derivations Array of production variable and tokens tuple
 * @returns Parse tree
 */
function generateParseTreeFromDerivations(variables, derivations) {
    const rootTree = [];
    const variablesSet = new Set(variables);
    // Global state to keep track of which derivation we are currently at
    let derivationNumber = 0;
    function recurse(derivation, childContainer) {
        const [productionVariable, productionRuleTokens] = derivation;
        // Create the parent node
        const parentNode = {
            [productionVariable]: []
        };
        // Loop through all the tokens
        for (let index = 0; index < productionRuleTokens.length; index += 1) {
            const token = productionRuleTokens[index];
            // Check if the token is a variable
            if (variablesSet.has(token)) {
                // Move to the next derivation
                derivationNumber += 1;
                // Make sure we haven't exhausted the derivations
                if (derivationNumber < derivations.length) {
                    recurse(derivations[derivationNumber], parentNode[productionVariable]);
                }
                else {
                    break;
                }
            }
            else {
                // Always push terminals as is
                parentNode[productionVariable].push(token);
            }
        }
        childContainer.push(parentNode);
    }
    recurse(derivations[0], rootTree);
    return rootTree[0];
}
exports.generateParseTreeFromDerivations = generateParseTreeFromDerivations;