assoc

hol88Lib.assoc : ''a -> (''a * 'b) list -> ''a * 'b

Searches a list of pairs for a pair whose first component equals a specified value.

assoc x [(x1,y1),...,(xn,yn)] returns the first (xi,yi) in the list such that xi equals x. The lookup is done on an eqtype, i.e., the SML implementation must be able to decide equality for the type of x.

Failure

Fails if no matching pair is found. This will always be the case if the list is empty.

Example

  - assoc 2 [(1,4),(3,2),(2,5),(2,6)];
 (2, 5) : (int * int)

Comments

Superseded by Lib.assoc and Lib.assoc1.

See also

hol88Lib.rev_assoc, Lib.assoc, Lib.assoc1