Toy - concatenative, functional, stack-based, truly postfix language.

toy-interpreter.js

const readline = require('readline');
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

let stack = [];
let consts = {
  swapd: '[[swap] dip]',
  popd: '[[pop] dip]',
  dupd: '[[dup] dip]'
};

const eval = (word) => {
  switch (word) {
    case "dup":
      stack.push(stack[stack.length-1]);
      break;
    case "swap":
      var tmp = stack.pop();
      var tmp2 = stack.pop();
      stack.push(tmp);
      stack.push(tmp2);
      break;
    case "dip":
      let prog = stack.pop();
      tmp = stack.pop();
      stack.push(prog);
      eval(".");
      stack.push(tmp);
      break;
    case "p":
    case "print":
      console.log(stack[stack.length-1]);
      break;
    case "pop":
      stack.pop();
      break;
    case "+":
      stack.push(parseFloat(stack.pop()) + parseFloat(stack.pop()));
      break;
    case "-":
      stack.push(parseFloat(stack.pop()) - parseFloat(stack.pop()));
      break;
    case "*":
      stack.push(parseFloat(stack.pop()) * parseFloat(stack.pop()));
      break;
    case "sqrt":
      stack.push(Math.sqrt(parseFloat(stack.pop())));
      break;
    case "/":
      stack.push(parseFloat(stack.pop()) / parseFloat(stack.pop()));
      break;
    case ">":
      stack.push(parseFloat(stack.pop()) > parseFloat(stack.pop()));
      break;
    case ">=":
      stack.push(parseFloat(stack.pop()) > parseFloat(stack.pop()));
      break;
    case "<":
      stack.push(parseFloat(stack.pop()) < parseFloat(stack.pop()));
      break;
    case "<=":
      stack.push(parseFloat(stack.pop()) < parseFloat(stack.pop()));
      break;
    case "!=":
      stack.push(parseFloat(stack.pop()) != parseFloat(stack.pop()));
      break;
    case "==":
      stack.push(parseFloat(stack.pop()) == parseFloat(stack.pop()));
      break;
    case "?":
      var predicate = stack.pop();
      (predicate != '0' && predicate != 'false') ? eval(".") : stack.pop() && eval("."); 
      break;
    case "q":
    case "quit":
      process.exit();
      break;
    case "c":
    case "clear":
      stack = [];
      break;
    case ".":
      let item = stack.pop();
      let lambda = item.match(/^\[(.*)\]$/);
      if (lambda) {
        lambda[1].split(/\s+(?=(?:[^\'"\[\]]*[\'"\[][^\'"\[\]]*[\'"\]])*[^\'"\[\]]*$)/).forEach(word=>eval(word))
      } else {
        stack.push(item);
      }
      break;
    case ":":
      consts[stack.pop()] = stack.pop();
      break;
    case "f":
    case "dump":
      stack.forEach(a => console.log(a));
      break;
    case "head":
      stack.push(stack.pop().match(/^\[([^\[\]]*)\]$/)[1].split(/\s+(?=(?:[^\'"\[\]]*[\'"\[][^\'"\[\]]*[\'"\]])*[^\'"\[\]]*$)/)[0]);
      break;
    case "tail":
      let content = stack.pop().match(/^\[([^\[\]]*)\]$/)[1].split(/\s+(?=(?:[^\'"\[\]]*[\'"\[][^\'"\[\]]*[\'"\]])*[^\'"\[\]]*$)/);
      content.shift();
      stack.push("[" + content.join(" ") + "]");
      break;
    case "cons":
      stack.push("[" + stack.pop() + " " + stack.pop() + "]");
      break;
    case "map":
      let array = stack.pop().match(/^\[([^\[\]]*)\]$/)[1].split(/\s+(?=(?:[^\'"\[\]]*[\'"\[][^\'"\[\]]*[\'"\]])*[^\'"\[\]]*$)/);
      let fn = stack.pop();
      stack.push("[" + array.map(item => {
        stack.push(item);
        stack.push(fn);
        eval(".");
        return stack.pop();}).join(" ") +"]");
      break;
    case "concat": // sezere dve makra a spoji je do jednoho
      stack.push("[" + stack.pop().match(/\[(.*)\]/)[1] + " " + stack.pop().match(/\[(.*)\]/)[1] + "]");
      break;
    case "quote":
      stack.push("[" + stack.pop() + "]");
      break;
    default:
      var isquoted;
      if (isquoted = word.toString().match(/^\[(.*)\]/)) {
        stack.push(word);
      } else {
        if (consts[word]) {
          eval(consts[word]); eval(".");
        } else {
          stack.push(word);
        }          
      }
  }
};

rl.on('line', (input) => {
  let wordlist = input.split(/\s+(?=(?:[^\'"\[\]]*[\'"\[][^\'"\[\]]*[\'"\]])*[^\'"\[\]]*$)/);
  wordlist.forEach(word => eval(word));
});