My purpose is simple, data type of the input is depending on the template bool:
template<bool isfloa>
class example{
public:
if (isfloa){
example(float p){printf("sizeof p: %d\n", sizeof(p))};
} else{
example(uint64_t p){printf("sizeof p: %d\n", sizeof(p))};
}
};
This cannot pass the compliation and I have the following solution (haven't test it):
using dataType = isfloa ? float : uint64_t;
example(dataType p){printf("sizeof p: %d\n", sizeof(p))};
I'd like to know if this works? And are there any other solutions? Thanks a lot.
CodePudding user response:
You can use std::conditional
template<bool isfloat>
class example{
public:
using value_type = std::conditional_t<isfloat,float,int>;
example(value_type p){printf("sizeof p: %d\n", sizeof(p));}
};
CodePudding user response:
In C 17 you can use sfinae to disable or enable member functions:
template<bool isfloa>
class example{
public:
template<bool isf = isfloa, std::enable_if_t<isf, int> = 0>
example(float p){ printf("sizeof p: %d\n", sizeof(p)); }
template<bool isf = isfloa, std::enable_if_t<!isf, int> = 0>
example(uint64_t p){ printf("sizeof p: %d\n", sizeof(p)); }
}
};
In C 20 you can simply use the requires
keyword:
template<bool isfloa>
class example{
public:
example(float p) requires(isfloa)
{ printf("sizeof p: %d\n", sizeof(p)); }
example(uint64_t p) requires(!isfloa)
{ printf("sizeof p: %d\n", sizeof(p)); }
}
};
CodePudding user response:
Prefer using normal overloading of functions, then after that switch to templates where needed. In this case reuse of the same code for both floating point types.
#include <type_traits> // header file for all kinds of type related checks at compile time
#include <iostream>
// for std::uint64_t only just use standard overloading
// NO need to overuse templates and template specializations where none is needed.
void example(const std::uint64_t value)
{
std::cout << "std::uint64_t, value = " << value << "\n";
}
// use SFINAE (std::enable_if_t) to enable this version of the function only for floating point types
template<typename type_t>
static inline std::enable_if_t<std::is_floating_point_v<type_t>, void> example(const type_t& value)
{
std::cout << "floating point value, value = " << value << "\n";
}
int main()
{
double fp{ 3.14159265 };
example(fp);
std::uint64_t value{ 42 };
example(value);
return 0;
}