const reduce_op = (op, def) => {
  let fn = ''
  + 'function () {'
  + '  return Array.from(arguments)'
  + '  .reduce((a, n) => typeof n === "undefined" ? a : (a ' + op + ' n), '+ def +')'
  return eval(fn)
}
// every programmer should implement a lisp interpreter once in their life
const fns = '+,0:-,0:*,1:/,1'.split(':').map(p => p.split(',')).map(reduce_op.apply.bind(null))