lambda-calculus-with-js/examples/list.test.js

Using JS' anonymous functions to perform lambda calculus

import t from 'tape';
import { fI, test } from '..';
import { getLambdaEq } from '../test';
import { I } from './combinatory';
import { deletedHead, deletedMany, deletedTail, deList, getList, head, indexed, l0, pushedHead, pushedTail, reversed, tail, } from './list';
import { deNumber, getNumber } from './number';
import { tuple } from './tuple';
t('list', t => {
    const eqL = getLambdaEq(t);
    eqL(getList([]), l0);
    eqL(getList([fI[1], fI[2], fI[3]]), tuple(F => F(fI[1])(fI[2])(fI[3]))(getNumber(3)));
    eqL(getList([I, pushedHead, deletedTail]), tuple(F => F(I)(pushedHead)(deletedTail))(getNumber(3)));
    t.deepEqual(deList(getList([fI[1], fI[3], fI[5]])), [fI[1], fI[3], fI[5]]);
    const sigTs = [
        [deletedHead, l => getList(l.slice(1))],
        [head, l => l[0]],
        [reversed, l => getList(l.slice().reverse())],
        [tail, l => l[l.length - 1]],
        [deletedTail, l => getList(l.slice(0, -1))],
    ];
    const binTs = [
        [pushedHead, (l, x) => getList([x, ...l])],
        [pushedTail, (l, x) => getList([...l, x])],
        [deletedMany, (l, n) => getList(l.slice(deNumber(n)))],
        [indexed, (l, i) => l[deNumber(i)]],
    ];
    const rand = (n = 50) => Math.ceil(Math.random() * n);
    function randomList() {
        const len = rand() + 1;
        const r = [];
        for (let i = 0; i < len; i++) {
            r.push(fI[rand()]);
        }
        return r;
    }
    const info = (fn, r) => `${fn.name} with ${r.map(n => test(n).toLambda(true))}`;
    for (let i = 0; i < 50; i++) {
        const r = randomList();
        for (const [fn, cm] of sigTs) {
            eqL(fn(getList(r)), cm(r), info(fn, r));
        }
        for (const [fn, cm] of binTs) {
            const n = rand(r.length - 1);
            const x = getNumber(n);
            eqL(fn(getList(r))(x), cm(r, x), info(fn, r) + ` ${n}`);
        }
    }
    t.end();
});