Searches a list of pairs for a pair whose first component equals a
specified value.
DESCRIPTION
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.
FAILURE
Never fails.
EXAMPLE
- assoc1 2 [(1,4),(3,2),(2,5),(2,6)];
> val it = SOME (2, 5) : (int * int)option