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assoc2                                                           (Lib)
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assoc2 : ''a -> ('b * ''a) list -> ('b * ''a)option

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

KEYWORDS
list.

DESCRIBE
An invocation {assoc2 y [(x1,y1),...,(xn,yn)]} returns {SOME (xi,yi)}
for the first {(xi,yi)} in the list such that {yi} equals
{y}. 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 {y}.

FAILURE
Never fails.

EXAMPLE

- assoc2 2 [(1,4),(3,2),(2,5),(2,6)];
> val it = SOME (3, 2) : (int * int) option




SEEALSO
Lib.assoc, Lib.assoc1, Lib.rev_assoc, Lib.mem, Lib.tryfind,
Lib.exists, Lib.all.

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