C宏函数重载

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  • 理论上，宏函数是不能重载的，第二个宏会直接覆盖掉第一个
  • 但我今天看到了一个非常sao优雅的方法，可以功能上实现重载，原文在这里
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#define OneArgument(a) // ...action with one argument
#define TwoArguments(a, b) // ...action with two arguments
 
#define GetMacro(_1, _2, NAME, ...) NAME
#define Macro(...) GetMacro(__VA_ARGS__, TwoArguments, OneArgument, ...)(__VA_ARGS__)
 
// usage:
Macro(a); // OneArument(a) is called
Macro(a, b);  // TwoArguments(a, b) is called

  • 其中，__VA_ARGS__是参数...的展开

  • 以此类推，三个参数的重载也是能实现的

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#define OneArgument(a) // ...action with one argument
#define TwoArguments(a, b) // ...action with two arguments
#define ThreeArguments(a, b, c) // ...action with three arguments
 
#define GetMacro(_1, _2, _3, NAME, ...) NAME
#define Macro(...) GetMacro(__VA_ARGS__, ThreeArguments, TwoArguments, OneArgument, ...)(__VA_ARGS__)
 
// usage:
Macro(a); // OneArument(a) is called
Macro(a, b);  // TwoArguments(a, b) is called
Macro(a, b, c);  // ThreeArguments(a, b, c) is called