[Pharo-users] Equality and hash

[Trussardi Dario Romano]

Ciao,

        i works with Pharo 4.0 environment. 

        I have a class Product  with some instance variable and the      =      
method set to:

        = anItem

        anItem ifNil:[^false]. 
        
        anItem class = self class ifFalse:[ ^false].
        
        ^  rfrConsegna  = anItem rfrConsegna 
                                and:[ rfrSubTable  = anItem rfrSubTable
                                        and:[ rfrDcm = anItem rfrDcm
                                                and:[ indexRiga = anItem 
indexRiga
                                                        and:[ referenceTime = 
anItem referenceTime 
                                                                and:[ consumer 
= anItem consumer
                                                                        and:[ 
item = anItem item
                                                                                
and:[ opzioniVoce  = anItem opzioniVoce
                                                                ]]]]]]]
        
        Some of these variables are instances  of classes with specific 
implementation and some variables themselves.


        I set the relative hash method to:

        hash
        
        ^ rfrConsegna hash
                bitXor:( rfrSubTable  hash
                        bitXor: ( rfrDcm hash
                                bitXor: ( indexRiga hash
                                        bitXor: ( referenceTime hash
                                                bitXor: ( consumer   hash
                                                        bitXor: ( item   hash
                                                                bitXor: ( 
opzioniVoce  hash
                                                
                                )))))))

        Now when add some setup instances of class Product  to a bag,

                 the relative inspector report 

                some aProduct entry but with some Occurences of this set to 0.

                aProduct1       3
                aProduct2       0
                aProduct3       0       


        Some consideration about it ?

        Some references about hash implementations ?

        Thanks,

                Dario