nock

A small Nock interpreter written in TypeScript. Use it either:

• as an interactive REPL, or
• as a module for evaluating Nock formulas from your own code.

Install

As a library

yarn add @tdjsnelling/nock

To try the REPL

git clone https://github.com/tdjsnelling/nock
yarn install
yarn build
yarn start:repl

What you can do in the REPL

• Paste/type a Nock expression in the bracketed, space-separated form.
• The REPL will parse it and evaluate it, printing the result.

Using as a module

The package entry point exports:

• parse(input: string) to turn a string into a Nock cell (AST/noun structure)
• the public types from types
• the interpreter functionality as default

Basic pattern

import Nock, { parse } from "nock";

const formula = parse("[42 0 1]");
const subject = formula[0];  // 42
const argument = formula[1]; // [0, 1]

const interpreter = new Nock();

const result = interpreter.nock(subject, argument);

console.log(result);

Interpreter options

The interpreter constructor can take some extra options:

• onHint: the function to call for the 'hint' opcode (11). Must return a noun (in which case this noun is the result of the evaluation), or null (in which case the hint acts as a side effect and normal evaluation of the operation proceeds).
• debug: enable debugging features.
• customDebug: by default, if debug is enabled, console.log is used to print helpful info during evaluation. This default behaviour can be replaced by providing a customDebug function which receives the parameters that would ordinarily be logged to the console.

const interpreter = new Nock({
  onHint: (tag: Noun, clue: Noun | null, subject: Noun, argument: Cell) => Noun | null,
  debug: boolean,
  customDebug: (data: DebugPayload) => void,
})

Parsing only

If you only need parsing (e.g., to validate or transform input), you can do:

import { parse } from "nock";

const cell = parse("[[1 2] [3 4]]");

console.log(cell);

Utility functions

import { checkAtom, checkCell } from "nock";

checkAtom(42);     // Ok
checkAtom([0, 1]); // Exception

checkCell(42);     // Exception
checkCell([0, 1]); // Ok

TypeScript types

The package ships some TypeScript types:

• Atom: a natural number
• Cell: an ordered pair of nouns
• Noun: atom or cell

import type { Atom, Cell, Noun } from "nock";