如何使用#ifdef进行数据类型切换

Question

我正在使用visual studio c ++.我希望能够在双长和长双之间切换.如何在以下程序中使用#ifdef？我想使用更简单的解决方案来处理多个printf的情况.

//#define TYPE_SWITCH
#ifdef TYPE_SWITCH
      typedef double myType;
#else
      typedef long long myType;
#end

.
.
.
int main()
{
     myType a;
     #ifdef TYPE_SWITCH
        printf ("my value is %lf",a);      // I have many printf or scanf and I want to use a simple macro here
     #else
        printf ("your value is %l",a/10);      // I have many printf or scanf and I want to use a simple macro here
     #endif

}

Answer 1

你可以使用这样的东西:

//#define TYPE_SWITCH
#ifdef TYPE_SWITCH
      typedef double myType;
      #def PATTERN_MY_TYPE "%lf"
      #def MODIFICATOR(a) (a)
#else
      typedef long long myType;
      #def PATTERN_MY_TYPE "%l"
      #def MODIFICATOR(a) (a/10)
#end
#def PATTERN_INT "%d"

//...

int main() {
     myType a;
     printf(PATTERN_MY_TYPE ", " PATTERN_INT, MODIFICATOR(a), 42);
}

竞争者可以在竞争时连接字符串,因此您可以使用"foo" "bar"创建字符串"foobar"与定义相同的工作.("foo" PATTERN_INT "bar"会产生"foo%dbar".