定义列表中的数字是否小于参数 - Scala

Question

Write a function which at the input takes two parameters: a list of integers and a number. The output returns a logical value. The function returns "true" if all numbers in the list are smaller than the number given in the second parameter. Otherwise, the function returns "false".

My code:

def less [A](list:List[A], number:Int):Boolean =
  if (list == Nil) false
  else ((List.head < number) && less[A](list:List.tail, number:Int))


less(List(1, 2, 3, 4), 5)
less(List(6,1,2,3),6)

Error message in IntelliJ:

On line 3: error: value head is not a member of object List

else (List.head < number) && less[A](list:List.tail, number:Int) //2

^

On line 3: error: type tail is not a member of object List

My question: What should I improve in this code to have it working?

Answer 1

Seems an awful lot like home work...

Scala has a forall function that can test a predicate against all values in the collection and returns a Boolean .

def less(xs: List[Int], number: Int) = xs.forall(x =>???)

Answer 2

I think you want something like this:

def less (list:List[Int], number:Int):Boolean =
  if (list == Nil) true
  else ((list.head < number) && less(list.tail, number))


less(List(1, 2, 3, 4), 5)//true
less(List(6,1,2,3),6)//false

But you should just use forall like @Brian said