DescriptionMacro <name> [(Parameter [, ...])] ... EndMacro
Macros are a very powerful feature, mainly useful for advanced programmers. A macro is a placeholder for some code (one keyword, one line or even many lines), which will be directly inserted in the source code at the place where a macro is used. In this, it differs from procedures, as the procedures doesn't duplicate the code when they are called.
The Macro : EndMacro declaration must be done before the macro will be called for the first time. Because macros will be completely replaced by their related code at compile time, they are not local to a procedure.
A macro can not have a return type nor typed parameters. When a macro has some parameters, they are replaced in the macro code by the literal expression which is passed to the called macro. No evaluation is done as this stage, which is very important to understand: the evaluation of a line is started once all the macros found on this line are expanded.
The macros are divided into two categories: simple (without parameters) and complex (with parameters, needs the parentheses when calling it). When using no parameters, it's possible to replace any word with another word (or any expression). The macros can't be called recursively.
Example: Simple macro
Macro MyNot Not EndMacro a = 0 If MyNot a ; Here the line will be expanded to : 'If Not a' Debug "Ok" EndIfWhen using parameters, it's possible to do very flexible macros. The special concatenation character '#' can be used to create new labels or keyword by mixing the macro code and the parameter expression (spaces are not accepted between each words by the concatenation character). It's also possible to define default values for parameters, so they can be omitted when calling the macro.
Example: Macro with parameter
Macro UMsgBox(Body) MessageRequester(UCase(Body), #PB_MessageRequester_Ok) EndMacro Text$ = "Hello World" UMsgBox("-"+Text$+"-") ; Here the line will be expanded like that: ; 'MessageRequester(UCase("-"+Text$+"-"), #PB_MessageRequester_Ok)'
Example: Macro with default parameter
Macro UMsgBox(Body = "Ha, no body specified") MessageRequester(UCase(Body), #PB_MessageRequester_Ok) EndMacro UMsgBox() ; Here the line will be expanded like that: ; 'MessageRequester(UCase("Ha, no body specified"), #PB_MessageRequester_Ok)'
Example: Macro parameter concatenation
Macro XCase(Type, Text) Type#Case(Text) EndMacro Debug XCase(U, "Hello") Debug XCase(L, "Hello")
Example: Advanced multi-line macro
Macro DoubleQuote " EndMacro Macro Assert(Expression) CompilerIf #PB_Compiler_Debugger ; Only enable assert in debug mode If Expression Debug "Assert (Line " + #PB_Compiler_Line + "): " + DoubleQuote#Expression#DoubleQuote EndIf CompilerEndIf EndMacro Assert(10 <> 10) ; Will display nothing Assert(10 <> 15) ; Should display the assert
UndefineMacro allows to undefine a previously defined macro, and redefine it in a different manner. Once the macro has been undefined, it is no more available for use.
Example: Undefine macro
Macro Test Debug "1" EndMacro Test ; Call the macro UndefineMacro Test ; Undefine the macro, it no more exists Macro Test ; Now we can redefine the macro Debug "2" EndMacro Test ; Call the macro
MacroExpandedCount allows to get the expanded count (number of time the macro has been expanded/called). It can be useful to generate unique identifiers in the same macro for every expansion (like label, procedure name etc.).
Example: Expanded count
Macro Test Debug MacroExpandedCount EndMacro Test ; Call the macro Test ; Call the macro Test ; Call the macro