@fauton/cfg/dist/generateVariableReferenceRecord.js

A package to work with context free grammars and LL1 parsers

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
/**
 * Return a record providing details of the location of each variable of the cfg
 * @param cfg Input context free grammar
 * @returns A record which provides info regarding the location of a variable
 */
function generateVariableReferenceRecord(cfg) {
    const { variables, productionRules } = cfg;
    const variableReferenceLocationRecord = {};
    // Loop through all variables
    variables.forEach(targetVariable => {
        // Array to keep track of all the locations outer variable is being referenced
        const variableReferences = [];
        // Loop though all variables again
        variables.forEach(productionVariable => {
            // Get the rules of the inner variable
            const rules = productionRules[productionVariable];
            // Loop through each rule
            rules.forEach((rule, ruleNumber) => {
                // Get the tokens of the rule
                const tokens = rule.split(" ");
                // Loop through all token 
                tokens.forEach((token, tokenNumber) => {
                    // Check if the token is the same as outer variable
                    if (token === targetVariable) {
                        variableReferences.push({
                            variable: productionVariable,
                            ruleNumber,
                            tokenNumber
                        });
                    }
                });
            });
        });
        variableReferenceLocationRecord[targetVariable] = variableReferences;
    });
    return variableReferenceLocationRecord;
}
exports.default = generateVariableReferenceRecord;