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Short-Circuiting with Logical Operators
Message
From
28/10/2014 03:32:58
 
 
To
28/10/2014 03:29:20
Lutz Scheffler
Lutz Scheffler Software Ingenieurbüro
Dresden, Germany
General information
Forum:
Visual FoxPro
Category:
Coding, syntax & commands
Environment versions
Visual FoxPro:
VFP 9 SP1
OS:
Windows Server 2003
Network:
Windows 2008 Server
Database:
MS SQL Server
Application:
Web
Miscellaneous
Thread ID:
01609995
Message ID:
01609999
Views:
58
>This is way a function should just do it's job (return a value) rather then having side effects like
>
>change of Parameters
>Output
>....
>
>VFP's style to mix up function and procedure (determination by the way to call instead of definition) makes this very unclear.


??

>Lutz
>
>>In one of my apps I just found and fixed a subtle edge-case bug caused by short-circuiting of logical operators. With my coding style I'm not usually vulnerable to it so it was interesting to be reminded of this feature of VFP.
>>
>>LOCAL ;
>>	llFlag
>>
>>llFlag = .F.
>>
>>CLEAR
>>
>>IF MyUDF( "First Argument" ) AND llFlag
>>
>>ENDIF
>>
>>IF llFlag AND MyUDF( "Second Argument" )
>>
>>ENDIF
>>
>>RETURN
>>
>>FUNCTION MyUDF ( tcArgumentPosition AS String )
>>
>>?"MyUDF( ) called when it is " + tcArgumentPosition
>>
>>ENDFUNC
>>
Gregory
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