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-- File: Recognizer.cdl
-- Created: Mon Feb 3 16:31:47 1992
-- Author: Christian CAILLET
-- <cky@phobox>
---Copyright: Matra Datavision 1992
deferred generic class Recognizer from Interface
(TheKey as any;
TheResul as Transient)
inherits Transient
---Purpose : Defines a correspondance between an object to be recognized,
-- of type (Kind) TheKey, and a result of the recognition. There
-- can be no correspondance. When an object is recognized, the
-- returned result is empty : a Recognizer is not aimed to make
-- a transfer but to initiate it by giving a correspondant
--
-- A Recognizer can be compound, that is, in addition to its own
-- Eval method if this one has failed, it can ask another
-- Recognizer to work, and so on : See method Add
raises NoSuchObject
is
Initialize;
---Purpose : Assumes that no result has yet been recognized
Evaluate (me : mutable; akey : TheKey; res : out mutable TheResul)
returns Boolean;
---Purpose : Evaluates if recognition has a result, returns it if yes
-- In case of success, Returns True and puts result in "res"
-- In case of Failure, simply Returns False
-- Works by calling deferred method Eval, and in case of failure,
-- looks for Added Recognizers to work
Result (me) returns mutable TheResul raises NoSuchObject;
---Purpose : Returns result of last recognition (call of Evaluate)
Add (me : mutable; reco : mutable Recognizer);
---Purpose : Adds a new Recognizer to the Compound, at the end
-- Several calls to Add work by adding in the order of calls :
-- Hence, when Eval has failed to recognize, Evaluate will call
-- Evaluate from the first added Recognizer if there is one,
-- and to the second if there is still no result, and so on
SetOK (me : mutable; aresult : mutable TheResul) is protected;
---Purpose : Records the result of the recognition. Called by specific
-- method Eval to record a result : after calling it, Eval has
-- finished and can return
SetKO (me : mutable) is protected;
---Purpose : Records that recognition gives no result
Eval (me : mutable; akey : TheKey) is deferred protected;
---Purpose : THIS METHOD DEFINES THE RECOGNITION PROTOCOL, it is proper to
-- each precise type of Recognizer
-- For a suitable type of akey, it calls SetOK(result) where
-- result is an empty result of appropriate type, then returns
fields
theres : TheResul; -- storing result of last evaluation
hasnext : Boolean;
thenext : Recognizer; -- managing compound definition
end Recognizer;
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