Get min/max int in a list of tuples of (int, string) in PolyML

Question

I have seen this question for Python, But I have the same question for SML (PolyMl).

I want to create a function to extract from a list of tuples (int, string) the string value of the tuple with minimum int.

For example, if I have this list:

l = [('a', 5), ('b', 3), ('c', 1), ('d', 6)]

The output should be 'c', because the minimum integer is in the tuple ('c', 1). Thank You!

gruenewa · Answer 1 · 2015-02-18T20:56:22.847

2

val l = [(#"a", 5), (#"b", 3), (#"c", 1), (#"d", 6)]

fun min [] = NONE
  | min [x] = SOME x
  | min ((c1,n1) :: (c2,n2) :: xs) = if n1 < n2 then
                                       min ((c1,n1) :: xs) 
                                     else
                                       min ((c2,n2) :: xs)

val SOME (c,_) = min l

edited Feb 18 '15 at 20:56

answered Feb 18 '15 at 20:50

gruenewa

1,666
11
16

score 0 · Answer 2 · answered Mar 01 '16 at 18:42

val lst = [(#"a", 5), (#"b", 3), (#"c", 1), (#"d", 6)];

(* The first item of a tuple is fetched with #1. *)
#1(List.foldl
    (fn ((new as (_,n)), (old as (_,n0))) =>
      if n < n0 then new else old)
    (hd lst)
    (tl lst));

(* val it = #"c" : char *)

Get min/max int in a list of tuples of (int, string) in PolyML

2 Answers2