tom-weatherhead/thaw-interpreter

// src/languages/lambda-calculus-augmented-syntax/script-executor.ts

// Execute LCAug scripts via e.g. $ intrprtr lcaug file.lca

import { createReadStream } from 'fs';
import { createInterface } from 'readline';

import { LanguageSelector } from 'thaw-interpreter-types';

import { createTokenizer } from 'thaw-lexical-analyzer';

import { createParser } from 'thaw-parser';

// BetaReductionStrategy,
import { churchNumeralToInteger, createGrammar, ILCExpression, reduce } from 'thaw-grammar';

export async function scriptExecutorLCAug(filename: string): Promise<void> {
    // console.log('filename is:', filename);

    const fileStream = createReadStream(filename);

    const rl = createInterface({
        input: fileStream,
        crlfDelay: Infinity
    });
    // Note: we use the crlfDelay option to recognize all instances of CR LF
    // ('\r\n') in input.txt as a single line break.

    let expressionAsString = '';

    for await (const line of rl) {
        // Each line in input.txt will be successively available here as `line`.
        // console.log(`Line from file: ${line}`);

        if (line.length === 0 || line.match(/^\s*$/) || line.match(/^\s*#/)) {
            continue;
            // } else if (line.match(/^+β([A-Z]+)/)) { // Specify a Beta-reduction strategy
            // ...
            //     continue;
            // }
        }

        expressionAsString = expressionAsString + line + ' ';
    }

    console.log(`\nExpression as string: ${expressionAsString}\n`);

    const ls = LanguageSelector.LambdaCalculusWithAugmentedSyntax;
    const grammar = createGrammar(ls);
    const tokenizer = createTokenizer(grammar.defaultLexicalAnalyzer, ls);
    const parser = createParser(grammar.defaultParser, grammar);
    const expr = parser.parse(tokenizer.tokenize(expressionAsString)) as ILCExpression;

    console.log(`Parsed expression: ${expr}\n`);

    const result = reduce(
        expr
        // , options: {
        //     readonly strategy?: BetaReductionStrategy;
        //     readonly generateNewVariableName?: () => string;
        //     readonly maxDepth?: number;
        // } = {}
    );
    const resultAsInteger = churchNumeralToInteger(result);
    let resultAsString: string;

    if (!Number.isNaN(resultAsInteger)) {
        resultAsString = `Integer ${resultAsInteger}`;
    } else {
        resultAsString = `${result}`;
    }

    console.log(`Reduced expression: ${resultAsString}`);
}