@fauton/cfg/dist/validateCfg.js

A package to work with context free grammars and LL1 parsers

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.validateCfg = void 0;
/**
 * Validates a cfg
 * @param cfg Input cfg to validate
 */
function validateCfg(cfg) {
    const { startVariable, terminals, productionRules, variables } = cfg;
    // Check if all the variables is present in transition record
    const productionRulesEntries = Object.entries(productionRules);
    if (productionRulesEntries.length !== variables.length) {
        throw new Error('All variables must be present in the transition record');
    }
    const terminalsSet = new Set(terminals);
    const variablesSet = new Set(variables);
    // Validate that all the keys of transition record are variables
    productionRulesEntries.forEach(([productionRuleVariable, productionRuleSubstitutions]) => {
        if (!variablesSet.has(productionRuleVariable)) {
            throw new Error(`Transition record contains a variable ${productionRuleVariable}, that is not present in variables array`);
        }
        // Check if all the substitutions contain either variable or terminal
        productionRuleSubstitutions.forEach((productionRuleSubstitution) => {
            const tokens = productionRuleSubstitution.split(' ');
            for (let index = 0; index < tokens.length; index += 1) {
                const productionRuleSubstitutionToken = tokens[index];
                // Check if the letter is a terminal
                const isTerminal = terminalsSet.has(productionRuleSubstitutionToken);
                // Check if the letter is a variable
                const isVariable = variablesSet.has(productionRuleSubstitutionToken);
                if (!isTerminal && !isVariable) {
                    throw new Error(`Transition record substitution chunk ${productionRuleSubstitutionToken} is neither a variable nor a terminal`);
                }
            }
        });
    });
    // Check if the starting variable is part of variables
    if (!variablesSet.has(startVariable)) {
        throw new Error(`Starting variable must be part of variables array`);
    }
}
exports.validateCfg = validateCfg;