1\DOC assoc2
2
3\TYPE {assoc2 : ''a -> ('b * ''a) list -> ('b * ''a)option}
4
5\SYNOPSIS
6Searches a list of pairs for a pair whose second component equals a specified
7value.
8
9\KEYWORDS
10list.
11
12\DESCRIBE
13An invocation {assoc2 y [(x1,y1),...,(xn,yn)]} returns {SOME (xi,yi)}
14for the first {(xi,yi)} in the list such that {yi} equals
15{y}. Otherwise, {NONE} is returned. The lookup is done on an eqtype,
16i.e., the SML implementation must be able to decide equality for the
17type of {y}.
18
19\FAILURE
20Never fails.
21
22\EXAMPLE
23{
24- assoc2 2 [(1,4),(3,2),(2,5),(2,6)];
25> val it = SOME (3, 2) : (int * int) option
26}
27
28
29\SEEALSO
30Lib.assoc, Lib.assoc1, Lib.rev_assoc, Lib.mem, Lib.tryfind, Lib.exists,
31Lib.all.
32
33\ENDDOC
34