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-- File: TCollection_MapHasher.cdl
-- Created: Thu Jan 7 15:58:43 1993
-- Author: Remi LEQUETTE
-- <rle@phylox>
---Copyright: Matra Datavision 1993
generic class MapHasher from TCollection (Key as any)
---Purpose: A hasher on the keys of a map instantiated from the
-- Collections component.
-- A hasher provides two functions:
-- - The hashing function (HashCode) transforms a key
-- into a bucket index in the map. The number of values
-- that can be computed by the hashing function is equal
-- to the number of buckets in the map.
-- - IsEqual is the equality test between two keys.
-- Hashers are used as parameters in generic maps
-- provided by the Collections component.
-- MapHasher is a generic class which depends on the type
-- of keys, provided that Key is a type from the Standard
-- package. In such cases MapHasher may be directly
-- instantiated with Key. Note that the package TColStd
-- provides some of these instantiations.
-- But if Key is not a type from the Standard package you
-- must consider MapHasher as a template and build a class
-- which includes its functions, in order to use it as a hasher
-- in a map instantiated from the Collections component.
-- Note that TCollection_AsciiString and
-- TCollection_ExtendedString classes correspond to
-- these specifications, in consequence they may be used as
-- hashers: when Key is one of these two types you may just
-- define the hasher as the same type at the time of
-- instantiation of your map.
is
HashCode(myclass; K : Key; Upper : Integer) returns Integer;
---Level: Public
---Purpose: Returns a HasCode value for the Key <K> in the
-- range 0..Upper.
-- Default ::HashCode(K,Upper)
IsEqual(myclass; K1, K2 : Key) returns Boolean;
---Level: Public
---Purpose: Returns True when the two keys are the same. Two
-- same keys must have the same hashcode, the
-- contrary is not necessary.
-- Default K1 == K2
end MapHasher;
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