c++ - How to get float value from object wrapped float in the sam way? -

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pi'm trying wrap float, int, etc primitves value sparam class. have problem getting values struct. want use struct use example floats. 

   template<class t>     struct sparam     {         t value;          sparam()         {         }          operator t() const         {             return value;             }         };     sparam<float> a;     a.value = 4;     printf("%f", a); //<--this don't print a.value

the problem using "naked" sparam<float> a printf (or other function takes variable number of arguments, matter) compiler not know want pass float. why type-specific conversion not applied. if call function specific parameter type, say

void printfloat(float f) {     printf("%f", f);  } ... sparam<float> a; a.value = 4; printfloat(a);

then compiler figure out signature of printfloat conversion float needs applied, , work expected. of course can apply conversion manually:

printf("%f", (float)a);

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