\DOC assoc

\TYPE {assoc : ''a -> (''a * 'b) list -> 'b}

\SYNOPSIS
Searches a list of pairs for a pair whose first component equals a
specified value, then returns the second component of the pair.

\KEYWORDS
list.

\DESCRIBE
{assoc x [(x1,y1),...,(xn,yn)]} locates the first {(xi,yi)} in a left-to-right
scan of the list such that {xi} equals {x}. Then {yi} 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
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)];
> val it = 5 : int
}


\SEEALSO
Lib.assoc1, Lib.assoc2, Lib.rev_assoc, Lib.mem, Lib.tryfind, Lib.exists,
Lib.all.

\ENDDOC