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rev_assoc                                                   (hol88Lib)
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rev_assoc : ''a -> ('b * ''a) list -> 'b * ''a

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

DESCRIBE
{rev_assoc y [(x1,y1),...,(xn,yn)]} returns the first {(xi,yi)} in the list
such that {yi} equals {y}. 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)];
  (3, 2) : (int * int)


COMMENTS
Superseded by {Lib.rev_assoc} and {Lib.assoc2}.

SEEALSO
hol88Lib.assoc, Lib.rev_assoc, Lib.assoc2.

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