Lib.assoc : ''a -> (''a * 'b) list -> ''a * 'b
Searches a list of pairs for a pair whose first component equals a specified value.
Fails if no matching pair is found. This will always be the case if the list is empty.
- assoc 2 [(1,4),(3,2),(2,5),(2,6)]; > val it = (2, 5) : (int * int)