Workaround for macro functions
Posted: Sat Jun 27, 2009 8:00 am
I needed macro functions to greatly simplify error handling in one of my projects. I also made a feature request about it here:
http://www.purebasic.fr/english/viewtopic.php?t=37568
I did some brainstorming today and managed to find a workaround to get similar functionality of macro functions. The only difference is that it passes the result of the value/expression to a function which is typed. So it's not a "true" macro but it's perfect for integer results and other common types. It doesn't work for expressions so I've included a second macro If_ErrorHandler() to work around that as well.
http://www.purebasic.fr/english/viewtopic.php?t=37568
I did some brainstorming today and managed to find a workaround to get similar functionality of macro functions. The only difference is that it passes the result of the value/expression to a function which is typed. So it's not a "true" macro but it's perfect for integer results and other common types. It doesn't work for expressions so I've included a second macro If_ErrorHandler() to work around that as well.
Code: Select all
#ERR_SUCCESS=0
#ERR_CUSTOM=-1
Procedure _CopyResultInteger(Input, *Output.Integer)
If *Output
*Output\i=Input
EndIf
ProcedureReturn Input
EndProcedure
;/ Exit thread on negative return values
Macro ErrorHandler(Expression)
_CopyResultInteger(Expression,@ExpressionResult): If ExpressionResult<0: ProcedureReturn ExpressionResult: EndIf
EndMacro
Macro If_ErrorHandler(Expression)
_CopyResultInteger(Expression,@ExpressionResult): If ExpressionResult<0: ProcedureReturn ExpressionResult: EndIf: If ExpressionResult
EndMacro
Procedure SomeFunctonSuccess()
ProcedureReturn #ERR_SUCCESS ;/ Success
EndProcedure
Procedure SomeFunctonError()
ProcedureReturn #ERR_CUSTOM ;/ Some error
EndProcedure
Procedure Thread()
n=ErrorHandler(SomeFunctonSuccess())
;/ Comparison operator must always compare from left to right
If_ErrorHandler(SomeFunctonSuccess())=#ERR_SUCCESS
Debug "#ERROR_SUCCESS"
EndIf
n=ErrorHandler(SomeFunctonError())
Debug "This is never printed because the macro exits the procedure early"
ProcedureReturn #ERR_SUCCESS
EndProcedure
If Thread()=#ERR_CUSTOM
Debug "#ERROR_CUSTOM"
EndIf