General Computer Science; Problems and Solutions for ... - Kwarc

1.2.3 Inductively Defined Sets in SML
Problem 1.24: Declare an SML datatype pair representing pairs of integers and define SML
functions fst and snd where fst returns the first- and snd the second component of q the pair.
Moreover write down the type of the constructor of pair as well as of the two procedures fst and
snd.
Use SML syntax for the whole problem.
Solution:
datatype pair = pair of int * int; (* val pair = fn : int * int -> pair *)
fun fst(pair(x,_)) = x; (* val fst = fn : pair -> int *)
fun snd(pair(_,y)) = y; (* val snd = fn : pair -> int *)
25
8pt
8min