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Index > Macroinstructions > Singleton pattern

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bitRAKE



Joined: 21 Jul 2003
Posts: 2945
Location: vpcmipstrm
bitRAKE
Code:
macro __imp_ n {
        match =n,n \{
         display '__imp_' # `n,13,10
               extrn __imp_\#n :QWORD
         n equ __imp_\#n
    \}
    call [n]
}    
How it works? First, MACRO invocation replaces "n" in the MATCH line to become: MATCH =Name,Name. Next, if Name is referenced to another value with EQU then the MATCH will resolve to EQU value - which should not be Name. Otherwise Name does = Name.

Note how several macro calls result in only the first MATCH block being executed and all from the preprocessor because MATCH resolves EQU. This pattern can be used to create a list of unique items without searching the list for existing entries. The EQU could be a LOCAL name to encapsulate the abstraction.

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Post 16 Jun 2009, 05:35
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