Icy Hot

type temp
  = Hot of int
  | Icy of int

Implement the function

val reduce : temp list -> temp list

so that reduce l is the list gotten from l by the following reduction rule: if Hot i and Icy i are adjacent (in particular, they must be carrying the same value) in any order, then they cancel out and are removed from the list. This rule should be carried out until it is not possible to reduce the list any further.

let _ = assert (reduce [Hot 0;Icy 0] = [])
let _ = assert (reduce [Hot 0;Icy 1;Hot 1;Icy 0] = [])
let _ = assert (reduce [Hot 0;Hot 1;Icy 2;Hot 2;Hot 0;Icy 1] = [Hot 0;Hot 1;Hot 0;Icy 1])