-- File: Recognizer.cdl -- Created: Mon Feb 3 16:31:47 1992 -- Author: Christian CAILLET -- ---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;