Cassidoo's Interview Question #2 - Filter in Vlang

filter.v

fn basic_filter(input []int, operation fn(int) bool) []int {
  mut output := []int

  for value in input {
    if operation(value) {
      output << value
    }
  }
  return output
}

fn even_numbers(number int) bool {
  if number % 2 == 0 {
    return true
  }
  return false
}

fn odd_numbers(number int) bool {
  return !even_numbers(number)
}

fn truthy_numbers(number int) bool {
  if bool(number) {
    return true
  }
  return false
}

fn falsy_numbers(number int) bool {
  return !truthy_numbers(number)
}

fn main() {
  input := [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]

  result1 := basic_filter(input, even_numbers)
  result2 := basic_filter(input, odd_numbers)
  result3 := basic_filter(input, truthy_numbers)
  result4 := basic_filter(input, falsy_numbers)

  println('Filter in Vlang')
 
  println('Input: ' + input.str())

  println('Even numbers: ' + result1.str())

  println('Odd numbers: ' + result2.str())

  println('Truthy numbers: ' + result3.str())

  println('Falsy numbers: ' + result4.str())

  yr := input[1].str() + '' + input[9].str() + '' + input[1].str() + '' + input[9].str() + ''
  println('Happy $yr :D ~')
}