9

I'd like to create templated operations between different types (suppose this is the list: int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t, uint32_t, uint64_t, float, double).

Then I'd like to allow for a saturate_cast<>() function to take the input value, check if it's within the output type limits and saturate to those limits if needed.

The problem is that if I'm summing two int32_t, the default C++ operation has undefined behavior in case of overflow, so I would like to promote the operation to int64_t and use that type to perform the operation.

A tentative solution could be:

#include <cstdint>
#include <limits>

template<typename T1, typename T2> struct type_which_fits { using type = decltype(T1() + T2()); };
template<> struct type_which_fits<int32_t, int32_t> { using type = int64_t; };

template<typename T1, typename T2>
auto TAdd(T1 lhs, T2 rhs) {
    using type = typename type_which_fits<T1, T2>::type;
    return static_cast<type>(lhs) + static_cast<type>(rhs);
}

template<typename ODT, typename IDT>
ODT saturate_cast(const IDT& v) {
    if (v > std::numeric_limits<ODT>::max()) {
        return std::numeric_limits<ODT>::max();
    }
    if (v < std::numeric_limits<ODT>::min()) {
        return std::numeric_limits<ODT>::min();
    }

    return static_cast<ODT>(v);
}

int main()
{
    auto x = saturate_cast<int8_t>(TAdd(1, 1u));
    return 0;
}

Unfortunately, in this way I need to further specify all possible combinations of types, and I would just need these rules (to be verified in the given order):

  • if one of the types is floating point use the default promotions
  • if one of the types is 64 bits, promote to double
  • if one of the types is 32 bit, promote to 64 bits
  • otherwise use the default promotions

Moreover in the saturate_cast<>() a bunch of signed/unsigned warnings pop up, when the two types have not the same "signedness".

Again this can be solved by specializing on all possible combinations, but somehow it feels "wrong".

Can you suggest a solution to make this more flexible, the moment I'll need more types?

Costantino Grana
  • 3,132
  • 1
  • 15
  • 35
  • 3
    Which C++ version are we talking about? If you can use `if constexpr` you should be able to write down most of your rules in `saturate_cast`/`type_which_fits` very directly. – Max Langhof Jun 05 '19 at 11:07
  • 2
    would it be an option to check before the overflow happens? eg `a+b` overflows if `max - b > a` (for positives), then you could avoid switching to the bigger type – 463035818_is_not_an_ai Jun 05 '19 at 11:41

1 Answers1

7

Here's my approach by doing the steps:

  1. Find the superior type (the type that would yield if an operation was performed)

  2. promote the type to the next type according to your rules 1-4

  3. Perform the addition while casting both sides to the promoted type.

The superior type can be found by following the general rules:

  • floating point + anything -> floating point

  • if left and right have the same bit size choose larger one (unsigned beats signed)

  • else choose where sizeof() yields the largest

the last 2 steps can be guaranteed (and simplified) by making a helper struct which returns the larger type (ab)using std::numerical_limits<T>::digits which neatly does exactly what we want (also regarding the signed / unsignedness) since:

  • std::numerical_limits<int>::digits -> 31

  • std::numerical_limits<unsigned>::digits -> 32

This will work for all arithmetic types accordingly.

template<typename T, typename U>
struct larger_arithmetic_type {
    static_assert(std::is_arithmetic_v<T>, "T must be arithmetic");
    static_assert(std::is_arithmetic_v<U>, "U must be arithmetic");
    using type = typename std::conditional_t<(std::numeric_limits<T>::digits < std::numeric_limits<U>::digits), U, T>;
};

template<typename T, typename U>
using larger_arithmetic_type_t = typename larger_arithmetic_type<T, U>::type;

With this we can enable a struct arithmetic_superior_type (following said general rules) to find the superior type from integers and/or floating point numbers:

template<typename T, typename U>
struct arithmetic_superior_type {
    using type = typename 
        std::conditional_t<std::is_floating_point_v<T> && std::is_floating_point_v<U>, larger_arithmetic_type_t<T, U>,
        std::conditional_t<std::is_floating_point_v<T>, T, 
        std::conditional_t<std::is_floating_point_v<U>, U, 
        larger_arithmetic_type_t<T, U>>>>;

};

template<typename T, typename U>
using arithmetic_superior_type_t = typename arithmetic_superior_type<T, U>::type;

Therefore arithmetic_seperior_type_t<T, U> returns the type that +, -, * and / between T and U would yield:

arithmetic_superior_type_t<std::int32_t, float> a;          //-> float
arithmetic_superior_type_t<std::uint32_t, std::int32_t> b;  //-> std::uint32_t
arithmetic_superior_type_t<std::uint32_t, std::uint32_t> c; //-> std::uint32_t
arithmetic_superior_type_t<std::uint64_t, std::uint32_t> d; //-> std::uint64_t
arithmetic_superior_type_t<float, double> e;                //-> double
arithmetic_superior_type_t<std::uint16_t, std::int64_t> f;  //-> std::int64_t

Now as you said, this type alone is not enough. Overflow is possible therefore promote_superior_type is step 2 to receive the promotion of the superior type from T and U - a type which will definetely hold any addition result:

template<typename T, typename U>
struct promote_superior_type {
    using superior_type = arithmetic_superior_type_t<T, U>;

    using type = typename
        std::conditional_t<(sizeof(T) == 8u || sizeof(U) == 8u), double, 
        std::conditional_t<std::is_floating_point_v<superior_type>, superior_type, 
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int16_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int16_t, std::uint16_t>,
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int32_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int32_t, std::uint32_t>,
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int64_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int64_t, std::uint64_t>, double>>>>>;
};

template<typename T, typename U>
using promote_superior_type_t = typename promote_superior_type<T, U>::type;

Finally the add<T, U> function can be added, step 3:

template<typename T, typename U, typename R = promote_superior_type_t<T, U>>
constexpr R add(T a, U b) {
    return static_cast<R>(a) + static_cast<R>(b);
}

That's all that's needed. static_asserting for correct expected output considering every possible type matchup:

//8_t + U

auto add_i8_i8 =  add(std::int8_t(10),  std::int8_t(10));   //i8 + i8 -> i16
auto add_i8_u8 =  add(std::int8_t(10),  std::uint8_t(10));  //i8 + u8 -> u16
auto add_u8_u8 =  add(std::uint8_t(10), std::uint8_t(10));  //u8 + u8 -> u16
auto add_i8_i16 = add(std::int8_t(10),  std::int16_t(10));  //i8 + i16 -> i32
auto add_i8_u16 = add(std::int8_t(10),  std::uint16_t(10)); //i8 + u16 -> u32
auto add_u8_u16 = add(std::uint8_t(10), std::uint16_t(10)); //u8 + u16 -> u32
auto add_i8_i32 = add(std::int8_t(10),  std::int32_t(10));  //i8 + i32 -> i64
auto add_i8_u32 = add(std::int8_t(10),  std::uint32_t(10)); //i8 + u32 -> u64
auto add_u8_u32 = add(std::uint8_t(10), std::uint32_t(10)); //u8 + u32 -> u64
auto add_i8_i64 = add(std::int8_t(10),  std::int64_t(10));  //i8 + i64 -> d64
auto add_i8_u64 = add(std::int8_t(10),  std::uint64_t(10)); //i8 + u64 -> d64
auto add_u8_u64 = add(std::uint8_t(10), std::uint64_t(10)); //u8 + u64 -> d64
auto add_i8_f32 = add(std::int8_t(10),  float(10));         //i8 + f32 -> f32
auto add_u8_f32 = add(std::uint8_t(10), float(10));         //u8 + f32 -> f32
auto add_i8_d64 = add(std::int8_t(10),  double(10));        //i8 + d64 -> d64
auto add_u8_d64 = add(std::uint8_t(10), double(10));        //u8 + d64 -> d64

//16_t + U

auto add_i16_i16 = add(std::int16_t(10),  std::int16_t(10));  //i16 + i16 -> i32
auto add_i16_u16 = add(std::int16_t(10),  std::uint16_t(10)); //i16 + u16 -> u32
auto add_u16_u16 = add(std::uint16_t(10), std::uint16_t(10)); //u16 + u16 -> u32
auto add_i16_i32 = add(std::int16_t(10),  std::int32_t(10));  //i16 + i32 -> i64
auto add_i16_u32 = add(std::int16_t(10),  std::uint32_t(10)); //i16 + u32 -> u64
auto add_u16_u32 = add(std::uint16_t(10), std::uint32_t(10)); //u16 + u32 -> u64
auto add_i16_i64 = add(std::int16_t(10),  std::int64_t(10));  //i16 + i64 -> d64
auto add_i16_u64 = add(std::int16_t(10),  std::uint64_t(10)); //i16 + u64 -> d64
auto add_u16_u64 = add(std::uint16_t(10), std::uint64_t(10)); //u16 + u64 -> d64
auto add_i16_f32 = add(std::int16_t(10),  float(10));         //i16 + f32 -> f32
auto add_u16_f32 = add(std::uint16_t(10), float(10));         //u16 + f32 -> f32
auto add_i16_d64 = add(std::int16_t(10),  double(10));        //i16 + d64 -> d64
auto add_u16_d64 = add(std::uint16_t(10), double(10));        //u16 + d64 -> d64

//32_t + U

auto add_i32_i32 = add(std::int32_t(10),  std::int32_t(10));  //i32 + i32 -> i64
auto add_i32_u32 = add(std::int32_t(10),  std::uint32_t(10)); //i32 + u32 -> u64
auto add_u32_u32 = add(std::uint32_t(10), std::uint32_t(10)); //u32 + u32 -> u64
auto add_i32_i64 = add(std::int32_t(10),  std::int64_t(10));  //i32 + i64 -> d64
auto add_i32_u64 = add(std::int32_t(10),  std::uint64_t(10)); //i32 + u64 -> d64
auto add_u32_u64 = add(std::uint32_t(10), std::uint64_t(10)); //u32 + u64 -> d64 
auto add_i32_f32 = add(std::int32_t(10),  float(10));         //i32 + f32 -> f32
auto add_u32_f32 = add(std::uint32_t(10), float(10));         //u32 + f32 -> f32
auto add_i32_d64 = add(std::int32_t(10),  double(10));        //i32 + d64 -> d64
auto add_u32_d64 = add(std::uint32_t(10), double(10));        //u32 + d64 -> d64

//64_t + U

auto add_i64_i64 = add(std::int64_t(10),  std::int64_t(10));  //i64 + i64 -> d64
auto add_i64_u64 = add(std::int64_t(10),  std::uint64_t(10)); //i64 + u64 -> d64
auto add_u64_u64 = add(std::uint64_t(10), std::uint64_t(10)); //u64 + u64 -> d64
auto add_i64_f32 = add(std::int64_t(10),  float(10));         //i64 + f32 -> d64
auto add_u64_f32 = add(std::uint64_t(10), float(10));         //u64 + f32 -> d64
auto add_i64_d64 = add(std::int64_t(10),  double(10));        //i64 + d64 -> d64
auto add_u64_d64 = add(std::uint64_t(10), double(10));        //u64 + d64 -> d64


static_assert(std::is_same_v<decltype(add_i8_i8), std::int16_t>, "");
static_assert(std::is_same_v<decltype(add_i8_u8), std::uint16_t>, "");
static_assert(std::is_same_v<decltype(add_u8_u8), std::uint16_t>, "");
static_assert(std::is_same_v<decltype(add_i8_i16), std::int32_t>, "");
static_assert(std::is_same_v<decltype(add_i8_u16), std::uint32_t>, "");
static_assert(std::is_same_v<decltype(add_u8_u16), std::uint32_t>, "");
static_assert(std::is_same_v<decltype(add_i8_i32), std::int64_t>, "");
static_assert(std::is_same_v<decltype(add_i8_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_u8_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_i8_i64), double>, "");
static_assert(std::is_same_v<decltype(add_i8_u64), double>, "");
static_assert(std::is_same_v<decltype(add_u8_u64), double>, "");
static_assert(std::is_same_v<decltype(add_i8_f32), float>, "");
static_assert(std::is_same_v<decltype(add_u8_f32), float>, "");
static_assert(std::is_same_v<decltype(add_i8_d64), double>, "");
static_assert(std::is_same_v<decltype(add_u8_d64), double>, "");

static_assert(std::is_same_v<decltype(add_i16_i16), std::int32_t>, "");
static_assert(std::is_same_v<decltype(add_i16_u16), std::uint32_t>, "");
static_assert(std::is_same_v<decltype(add_u16_u16), std::uint32_t>, "");
static_assert(std::is_same_v<decltype(add_i16_i32), std::int64_t>, "");
static_assert(std::is_same_v<decltype(add_i16_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_u16_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_i16_i64), double>, "");
static_assert(std::is_same_v<decltype(add_i16_u64), double>, "");
static_assert(std::is_same_v<decltype(add_u16_u64), double>, "");
static_assert(std::is_same_v<decltype(add_i16_f32), float>, "");
static_assert(std::is_same_v<decltype(add_u16_f32), float>, "");
static_assert(std::is_same_v<decltype(add_i16_d64), double>, "");
static_assert(std::is_same_v<decltype(add_u16_d64), double>, "");

static_assert(std::is_same_v<decltype(add_i32_i32), std::int64_t>, "");
static_assert(std::is_same_v<decltype(add_i32_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_u32_u32), std::uint64_t>, "");
static_assert(std::is_same_v<decltype(add_i32_i64), double>, "");
static_assert(std::is_same_v<decltype(add_i32_u64), double>, "");
static_assert(std::is_same_v<decltype(add_u32_u64), double>, "");
static_assert(std::is_same_v<decltype(add_i32_f32), float>, "");
static_assert(std::is_same_v<decltype(add_u32_f32), float>, "");
static_assert(std::is_same_v<decltype(add_i32_d64), double>, "");
static_assert(std::is_same_v<decltype(add_u32_d64), double>, "");

static_assert(std::is_same_v<decltype(add_i64_i64), double>, "");
static_assert(std::is_same_v<decltype(add_i64_u64), double>, "");
static_assert(std::is_same_v<decltype(add_u64_u64), double>, "");
static_assert(std::is_same_v<decltype(add_i64_f32), double>, "");
static_assert(std::is_same_v<decltype(add_u64_f32), double>, "");
static_assert(std::is_same_v<decltype(add_i64_d64), double>, "");
static_assert(std::is_same_v<decltype(add_u64_d64), double>, "");

There's one uncertainty: 

i64 + f32 -> d64
u64 + f32 -> d64
//...
static_assert(std::is_same_v<decltype(add_i64_f32), double>, "");
static_assert(std::is_same_v<decltype(add_u64_f32), double>, "");

according to your rules it could also be:

i64 + f32 -> f32 
u64 + f32 -> f32 
//...
static_assert(std::is_same_v<decltype(add_i64_f32), float>, "");
static_assert(std::is_same_v<decltype(add_u64_f32), float>, "");

full code:

#include <type_traits>
#include <limits>
#include <cstdint>

template<typename T, typename U>
struct larger_arithmetic_type {
    static_assert(std::is_arithmetic_v<T>, "T must be arithmetic");
    static_assert(std::is_arithmetic_v<U>, "U must be arithmetic");
    using type = typename std::conditional_t<(std::numeric_limits<T>::digits < std::numeric_limits<U>::digits), U, T>;
};

template<typename T, typename U>
using larger_arithmetic_type_t = typename larger_arithmetic_type<T, U>::type;

template<typename T, typename U>
struct arithmetic_superior_type {
    using type = typename 
        std::conditional_t<std::is_floating_point_v<T> && std::is_floating_point_v<U>, larger_arithmetic_type_t<T, U>,
        std::conditional_t<std::is_floating_point_v<T>, T, 
        std::conditional_t<std::is_floating_point_v<U>, U, 
        larger_arithmetic_type_t<T, U>>>>;

};

template<typename T, typename U>
using arithmetic_superior_type_t = typename arithmetic_superior_type<T, U>::type;


template<typename T, typename U>
struct promote_superior_type {
    using superior_type = arithmetic_superior_type_t<T, U>;

    using type = typename
        std::conditional_t<(sizeof(T) == 8u || sizeof(U) == 8u), double, 
        std::conditional_t<std::is_floating_point_v<superior_type>, superior_type, 
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int16_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int16_t, std::uint16_t>,
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int32_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int32_t, std::uint32_t>,
        std::conditional_t<(std::numeric_limits<superior_type>::digits < std::numeric_limits<std::int64_t>::digits), std::conditional_t<std::is_signed_v<superior_type>, std::int64_t, std::uint64_t>, double>>>>>;
};

template<typename T, typename U>
using promote_superior_type_t = typename promote_superior_type<T, U>::type;

template<typename T, typename U, typename R = promote_superior_type_t<T, U>>
constexpr R add(T a, U b) {
    return static_cast<R>(a) + static_cast<R>(b);
}


int main() {
    arithmetic_superior_type_t<std::int32_t, float> a;          //-> float
    arithmetic_superior_type_t<std::uint32_t, std::int32_t> b;  //-> std::uint32_t
    arithmetic_superior_type_t<std::uint32_t, std::uint32_t> c; //-> std::uint32_t
    arithmetic_superior_type_t<std::uint64_t, std::uint32_t> d; //-> std::uint64_t
    arithmetic_superior_type_t<float, double> e;                //-> double
    arithmetic_superior_type_t<std::uint16_t, std::int64_t> f;  //-> std::int64_t


    //8_t + U

    auto add_i8_i8 =  add(std::int8_t(10),  std::int8_t(10));   //i8 + i8 -> i16
    auto add_i8_u8 =  add(std::int8_t(10),  std::uint8_t(10));  //i8 + u8 -> u16
    auto add_u8_u8 =  add(std::uint8_t(10), std::uint8_t(10));  //u8 + u8 -> u16
    auto add_i8_i16 = add(std::int8_t(10),  std::int16_t(10));  //i8 + i16 -> i32
    auto add_i8_u16 = add(std::int8_t(10),  std::uint16_t(10)); //i8 + u16 -> u32
    auto add_u8_u16 = add(std::uint8_t(10), std::uint16_t(10)); //u8 + u16 -> u32
    auto add_i8_i32 = add(std::int8_t(10),  std::int32_t(10));  //i8 + i32 -> i64
    auto add_i8_u32 = add(std::int8_t(10),  std::uint32_t(10)); //i8 + u32 -> u64
    auto add_u8_u32 = add(std::uint8_t(10), std::uint32_t(10)); //u8 + u32 -> u64
    auto add_i8_i64 = add(std::int8_t(10),  std::int64_t(10));  //i8 + i64 -> d64
    auto add_i8_u64 = add(std::int8_t(10),  std::uint64_t(10)); //i8 + u64 -> d64
    auto add_u8_u64 = add(std::uint8_t(10), std::uint64_t(10)); //u8 + u64 -> d64
    auto add_i8_f32 = add(std::int8_t(10),  float(10));         //i8 + f32 -> f32
    auto add_u8_f32 = add(std::uint8_t(10), float(10));         //u8 + f32 -> f32
    auto add_i8_d64 = add(std::int8_t(10),  double(10));        //i8 + d64 -> d64
    auto add_u8_d64 = add(std::uint8_t(10), double(10));        //u8 + d64 -> d64

    //16_t + U

    auto add_i16_i16 = add(std::int16_t(10),  std::int16_t(10));  //i16 + i16 -> i32
    auto add_i16_u16 = add(std::int16_t(10),  std::uint16_t(10)); //i16 + u16 -> u32
    auto add_u16_u16 = add(std::uint16_t(10), std::uint16_t(10)); //u16 + u16 -> u32
    auto add_i16_i32 = add(std::int16_t(10),  std::int32_t(10));  //i16 + i32 -> i64
    auto add_i16_u32 = add(std::int16_t(10),  std::uint32_t(10)); //i16 + u32 -> u64
    auto add_u16_u32 = add(std::uint16_t(10), std::uint32_t(10)); //u16 + u32 -> u64
    auto add_i16_i64 = add(std::int16_t(10),  std::int64_t(10));  //i16 + i64 -> d64
    auto add_i16_u64 = add(std::int16_t(10),  std::uint64_t(10)); //i16 + u64 -> d64
    auto add_u16_u64 = add(std::uint16_t(10), std::uint64_t(10)); //u16 + u64 -> d64
    auto add_i16_f32 = add(std::int16_t(10),  float(10));         //i16 + f32 -> f32
    auto add_u16_f32 = add(std::uint16_t(10), float(10));         //u16 + f32 -> f32
    auto add_i16_d64 = add(std::int16_t(10),  double(10));        //i16 + d64 -> d64
    auto add_u16_d64 = add(std::uint16_t(10), double(10));        //u16 + d64 -> d64

    //32_t + U

    auto add_i32_i32 = add(std::int32_t(10),  std::int32_t(10));  //i32 + i32 -> i64
    auto add_i32_u32 = add(std::int32_t(10),  std::uint32_t(10)); //i32 + u32 -> u64
    auto add_u32_u32 = add(std::uint32_t(10), std::uint32_t(10)); //u32 + u32 -> u64
    auto add_i32_i64 = add(std::int32_t(10),  std::int64_t(10));  //i32 + i64 -> d64
    auto add_i32_u64 = add(std::int32_t(10),  std::uint64_t(10)); //i32 + u64 -> d64
    auto add_u32_u64 = add(std::uint32_t(10), std::uint64_t(10)); //u32 + u64 -> d64 
    auto add_i32_f32 = add(std::int32_t(10),  float(10));         //i32 + f32 -> f32
    auto add_u32_f32 = add(std::uint32_t(10), float(10));         //u32 + f32 -> f32
    auto add_i32_d64 = add(std::int32_t(10),  double(10));        //i32 + d64 -> d64
    auto add_u32_d64 = add(std::uint32_t(10), double(10));        //u32 + d64 -> d64

    //64_t + U

    auto add_i64_i64 = add(std::int64_t(10),  std::int64_t(10));  //i64 + i64 -> d64
    auto add_i64_u64 = add(std::int64_t(10),  std::uint64_t(10)); //i64 + u64 -> d64
    auto add_u64_u64 = add(std::uint64_t(10), std::uint64_t(10)); //u64 + u64 -> d64
    auto add_i64_f32 = add(std::int64_t(10),  float(10));         //i64 + f32 -> d64
    auto add_u64_f32 = add(std::uint64_t(10), float(10));         //u64 + f32 -> d64
    auto add_i64_d64 = add(std::int64_t(10),  double(10));        //i64 + d64 -> d64
    auto add_u64_d64 = add(std::uint64_t(10), double(10));        //u64 + d64 -> d64


    static_assert(std::is_same_v<decltype(add_i8_i8), std::int16_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_u8), std::uint16_t>, "");
    static_assert(std::is_same_v<decltype(add_u8_u8), std::uint16_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_i16), std::int32_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_u16), std::uint32_t>, "");
    static_assert(std::is_same_v<decltype(add_u8_u16), std::uint32_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_i32), std::int64_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_u8_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_i8_i64), double>, "");
    static_assert(std::is_same_v<decltype(add_i8_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_u8_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_i8_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_u8_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_i8_d64), double>, "");
    static_assert(std::is_same_v<decltype(add_u8_d64), double>, "");

    static_assert(std::is_same_v<decltype(add_i16_i16), std::int32_t>, "");
    static_assert(std::is_same_v<decltype(add_i16_u16), std::uint32_t>, "");
    static_assert(std::is_same_v<decltype(add_u16_u16), std::uint32_t>, "");
    static_assert(std::is_same_v<decltype(add_i16_i32), std::int64_t>, "");
    static_assert(std::is_same_v<decltype(add_i16_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_u16_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_i16_i64), double>, "");
    static_assert(std::is_same_v<decltype(add_i16_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_u16_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_i16_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_u16_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_i16_d64), double>, "");
    static_assert(std::is_same_v<decltype(add_u16_d64), double>, "");

    static_assert(std::is_same_v<decltype(add_i32_i32), std::int64_t>, "");
    static_assert(std::is_same_v<decltype(add_i32_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_u32_u32), std::uint64_t>, "");
    static_assert(std::is_same_v<decltype(add_i32_i64), double>, "");
    static_assert(std::is_same_v<decltype(add_i32_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_u32_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_i32_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_u32_f32), float>, "");
    static_assert(std::is_same_v<decltype(add_i32_d64), double>, "");
    static_assert(std::is_same_v<decltype(add_u32_d64), double>, "");

    static_assert(std::is_same_v<decltype(add_i64_i64), double>, "");
    static_assert(std::is_same_v<decltype(add_i64_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_u64_u64), double>, "");
    static_assert(std::is_same_v<decltype(add_i64_f32), double>, "");
    static_assert(std::is_same_v<decltype(add_u64_f32), double>, "");
    static_assert(std::is_same_v<decltype(add_i64_d64), double>, "");
    static_assert(std::is_same_v<decltype(add_u64_d64), double>, "");
}
Stack Danny
  • 7,754
  • 2
  • 26
  • 55