assoc1 : ''a -> (''a * 'b) list -> (''a * 'b)option
Searches a list of pairs for a pair whose first component equals a specified value.
assoc1 x [(x1,y1),...,(xn,yn)] returns SOME (xi,yi) for the first pair (xi,yi) in the list such that xi equals x. Otherwise, NONE is returned. The lookup is done on an eqtype, i.e., the SML implementation must be able to decide equality for the type of x.
Never fails.
- assoc1 2 [(1,4),(3,2),(2,5),(2,6)]; > val it = SOME (2, 5) : (int * int)option