58faf91453
* *
% remove brandings and homepage [1] from copyright header. Pass 1 - using script.
[1] nobody has access to it anymore AFAIK - and it's also just
a redirect since long
! update url in copyright header
; this should make the diff between 3.4 and 3.2 easier to manage
106 lines
2.8 KiB
Plaintext
106 lines
2.8 KiB
Plaintext
/*
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* demonstration code for FOR EACH overloading
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*
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* Copyright 2007 Przemyslaw Czerpak <druzus / at / priv.onet.pl>
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*
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*/
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#include "hbclass.ch"
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proc main()
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local e, o
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? "FOR EACH e IN myclass1()"
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o := myclass1()
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for each e in o
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? e:__enumIndex(), "=>", e
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next
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? "FOR EACH e IN myclass1() DESCEND"
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for each e in o descend
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? e:__enumIndex(), "=>", e
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next
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?
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? "FOR EACH e IN myclass2()"
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o:=myclass2()
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for each e in o
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? e:__enumIndex(), "=>", e
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next
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? "FOR EACH e IN myclass2() DESCEND"
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for each e in o descend
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? e:__enumIndex(), "=>", e
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next
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return
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/* The first form of FOR EACH overloading
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* Can be use when all values can be calculated when FOR EACH starts
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* It overloads __enumStart() message which set base enumerator values.
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* for ascending iteration it sets: {"A","B","C"}
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* and for descending: {1, 2, 3}
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*/
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CREATE CLASS myclass1
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METHOD __enumStart( enum, lDescend )
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END CLASS
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METHOD __enumStart( enum, lDescend ) CLASS myclass1
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/* set base value for enumerator */
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/* important: the messages have to be send to the enumerator
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* reference (@enum) not directly to the enumerator enum
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*/
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(@enum):__enumBase( iif( lDescend, {1, 2, 3}, {"A","B","C"} ) )
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return .T. /* .F. means stop iteration */
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/* The second form of FOR EACH overloading
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* We are overloading the folowing messages:
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* __enumStart() // executed when FOR EACH starts
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* __enumSkip() // executed on each LOOP
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* __enumStop() // executed when FOR EACH stops
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* Such method can be used when we cannot calculate all values
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* when FOR EACH starts or such calculation is expensive so we
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* want to make them dynamically
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*/
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CREATE CLASS myclass2
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VAR value
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METHOD __enumStart( enum, lDescend )
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METHOD __enumSkip( enum, lDescend )
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METHOD __enumStop()
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END CLASS
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METHOD __enumStart( enum, lDescend ) CLASS myclass2
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/* Here we can have initialization code */
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::value := 0.00
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/* set enumerator value */
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(@enum):__enumValue( ::value )
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/* set enumerator index, to make it more funny for descend
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* iterations we will use negative indexes ;-)
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*/
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(@enum):__enumIndex( iif( lDescend, -1, 1 ) )
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return .T. /* continue iteration */
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METHOD __enumSkip( enum, lDescend ) CLASS myclass2
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if lDescend
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::value -= 3
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else
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::value += 3
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endif
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/* stop iteration when abs( ::value ) > 20 */
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if abs( ::value ) > 20
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return .F.
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endif
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/* set enumerator value */
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(@enum):__enumValue( ::value / 10.0 )
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/* the index is updated automatically but if we want some noncontinuous
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* indexes then here we can set it using (@enum):__enumIndex( nNeIndex )
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* message
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*/
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return .T. /* continue iteration */
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METHOD PROCEDURE __enumStop() CLASS myclass2
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/* Here we can have cleanup code */
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return
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