rev_assoc
Lib.rev_assoc : ''a -> ('b * ''a) list -> 'b
Searches a list of pairs for a pair whose second component equals a specified value.
An invocation rev_assoc y [(x1,y1),...,(xn,yn)] locates the first
(xi,yi) in a left-to-right scan of the list such that yi equals y.
Then xi is returned. The lookup is done on an eqtype, i.e., the SML
implementation must be able to decide equality for the type of y.
Failure
Fails if no matching pair is found. This will always be the case if the list is empty.
Example
> rev_assoc 2 [(1,4),(3,2),(2,5),(2,6)];
val it = 3: int
See also
Lib.assoc, Lib.assoc1,
Lib.assoc2, Lib.mem,
Lib.tryfind, Lib.exists,
Lib.all