code / tomo-koans

   1 # Reductions
   2 
   3 func main()
   4 
   5     # Reductions fold collections into a single value:
   6     assert (+: [1, 2, 3])! == ???
   7     assert (*: [2, 3, 4])! == ???
   8 
   9     # If an empty argument is given, a `none` value is returned
  10     empty : [Int] = []
  11     assert (+: empty) == none
  12 
  13     # Use `or` to provide a fallback:
  14     assert (+: empty) or 100 == ???
  15 
  16     # `_min_` and `_max_` work as reducers:
  17     assert (_max_: [10, 30, 20])! == ???
  18     assert (_min_.length: ["x", "abcd", "yz"])! == "???"
  19 
  20     # Comprehensions inside reductions:
  21     assert (+: i * 2 for i in [1, 2, 3])! == ???
  22 
  23     assert (+: i for i in 10 if i.is_prime())! == ???