@fauton/cfg/dist/parseWithLL1Table.js

A package to work with context free grammars and LL1 parsers

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.parseWithLL1Table = void 0;
const generateLL1ParsingTable_1 = require("./generateLL1ParsingTable");
const generateParseTreeFromDerivations_1 = require("./generateParseTreeFromDerivations");
const populateCfg_1 = require("./utils/populateCfg");
function parseWithLL1Table(inputCfg, textContent) {
    const derivations = [];
    const cfg = (0, populateCfg_1.populateCfg)(inputCfg);
    const { parseTable } = (0, generateLL1ParsingTable_1.generateLL1ParsingTable)(cfg);
    const ruleStack = ["$", cfg.startVariable];
    let lookAheadPointer = 0;
    let parsed = null;
    while (ruleStack.length !== 1 && lookAheadPointer !== textContent.length) {
        const variableAtStackTop = ruleStack.pop();
        if (variableAtStackTop === textContent[lookAheadPointer]) {
            lookAheadPointer += 1;
        }
        else {
            const char = textContent[lookAheadPointer];
            if (char in parseTable[variableAtStackTop]) {
                const ruleNumber = parseTable[variableAtStackTop][char];
                const productionRule = cfg.productionRules[variableAtStackTop][ruleNumber];
                const productionRuleTokens = productionRule.split(" ");
                ruleStack.push(...[...productionRuleTokens].reverse());
                derivations.push([variableAtStackTop, productionRuleTokens]);
            }
            else {
                parsed = false;
                break;
            }
        }
    }
    return {
        parsed: parsed !== null && parsed !== void 0 ? parsed : (ruleStack.length === 1 && ruleStack[0] === "$"),
        derivations,
        tree: (0, generateParseTreeFromDerivations_1.generateParseTreeFromDerivations)(cfg.variables, derivations)
    };
}
exports.parseWithLL1Table = parseWithLL1Table;