factorial

eve::factorial = functor<factorial_t>

inlineconstexpr

Callable Signatures

#include <eve/module/special.hpp>

Callable Signatures

namespace eve
{
   // Regular overload
   template <value T> constexpr as_wide_as_t<double,T> factorial(T x)           noexcept; // 1
 
   // Semantic options
   template <value T> constexpr as_wide_as_t<double,T> factorial[pedantic](T x) noexcept; // 2
 
   // Lanes masking
   constexpr auto factorial[conditional_expr auto c](value auto n)              noexcept; // 3
   constexpr auto factorial[logical_value auto m](value auto n)                 noexcept; // 3
}

Parameters

• n: input value.
• c: Conditional expression masking the operation.
• m: Logical value masking the operation.

Return value

1. The value of \( n!\) is returned. If the entry is of integral type a double based floating_value is returned. The call return a Nan for any entry which is not a flint or not positive.
2. With the pedantic option \(\Gamma(x+1)\) is returned. (more expansive)
3. The operation is performed conditionnaly

Warning

This function will overflow as soon as the input is greater than 171 for integral or double entries and if the entry is greater than 34 for float.

External references

• Wolfram MathWorld: Erf
• Wikipedia: Error Function

Example

// revision 1
#include <eve/module/special.hpp>
#include <iostream>
 
int main()
{
  eve::wide<float> wf([](auto i, auto c)->float{ return 2*(i+c/2);});
  eve::wide wf1{-3.0, 0.5, 3.0, 4.0};
  eve::wide wi = {93, 25, 32, 180, 1, 2, 3, 4};
  eve::wide<std::uint32_t> wu([](auto i, auto )->std::uint32_t{ return i;});
 
  std::cout << "<- wf            = " << wf << "\n";
  std::cout << "<- wf1           = " << wf1<< "\n";
  std::cout << "<- wi            = " << wi << "\n";
  std::cout << "<- wu            = " << wu << "\n";
 
  std::cout << "-> factorial(wf) = " << eve::factorial(wf) << "\n";
  std::cout << "-> factorial(wi) = " << eve::factorial(wi) << "\n";
  std::cout << "-> factorial(wu) = " << eve::factorial(wu) << "\n";
  std::cout << "-> factorial(wf1) = " << eve::factorial(wf1) << "\n";
  std::cout << "-> factorial[pedantic](wf1) = " << eve::factorial[eve::pedantic](wf1) << "\n";
 
}