@thi.ng/pointfree/cond.js

Pointfree functional composition / Forth style stack execution engine

import { illegalState } from "@thi.ng/errors/illegal-state";
import { $ } from "./safe.js";
import { nop } from "./stack.js";
import { $stackFn } from "./word.js";
const defCond = (_then, _else = nop) => (ctx) => {
  $(ctx[0], 1);
  return $stackFn(ctx[0].pop() ? _then : _else)(ctx);
};
const condq = (ctx) => {
  const stack = ctx[0];
  $(stack, 3);
  const _else = stack.pop();
  const _then = stack.pop();
  return $stackFn(stack.pop() ? _then : _else)(ctx);
};
const whenq = (ctx) => {
  const stack = ctx[0];
  $(stack, 2);
  const _then = stack.pop();
  return stack.pop() ? $stackFn(_then)(ctx) : ctx;
};
const defCases = (cases) => (ctx) => {
  $(ctx[0], 1);
  const stack = ctx[0];
  const tos = stack.pop();
  const cas = cases[tos];
  if (cas !== void 0) {
    return $stackFn(cas)(ctx);
  }
  if (cases.default) {
    stack.push(tos);
    return $stackFn(cases.default)(ctx);
  }
  return illegalState(`no matching case for: ${tos}`);
};
const casesq = (ctx) => {
  const stack = ctx[0];
  $(stack, 2);
  return defCases(stack.pop())(ctx);
};
export {
  casesq,
  condq,
  defCases,
  defCond,
  whenq
};