code: function unless(pred, f) {
    if(!isPredOrFunc(pred)) {
      throw new TypeError(
        'unless: Pred or predicate function required for first argument'
      )
    }
  
    if(!isFunction(f)) {
      throw new TypeError(
        'unless: Function required for second argument'
      )
    }
  
    return x =>
      !predOrFunc(pred, x) ? f(x) : x
  }
docs: unless : (a -> Boolean) | Pred -> (a -> b) -> a | b