validator.js

function or(...ps) {
  return (x) => {
    for(var i = 0; i< ps.length;i++)
      if (ps[i](x)) return true
    return false
  }
}
function i(x) {
  return Number.isInteger(x)
}
function s(x) {
  return (i) => i == x
}
function a(...ps) {
  return (is) => {
    if (is.length != ps.length) return false;
    for(var i=0; i< is.length; i++)
      if(!ps[i](is[i])) return false;
    return true;
  }
}
function o(os) {
  return (is) => {
    for(var i in os) {
      if(!os[i](is[i])) return false
    }
    return true
  }
}
function delay(f) {
  return (i) => f()(i)
}
function assert(a) {
  if(!a) throw a;
}

var e = delay(()=>or(i,a(s("add"),e,e),a(s("mul"),e,e)))
assert(e(1));
assert(e(["add",1,["mul",2,3]]));
var t = delay(()=>or(i,o({tag:s("add"),l:t,r:t}),o({tag:s("mul"),l:t,r:t})))
assert(t(1));
assert(t({tag:"add",l:1,r:{tag:"mul",l:2,r:3}}))