trunc

auto eve::trunc = functor<trunc_t>

inlineconstexpr

Header file

#include <eve/module/core.hpp>

Callable Signatures

namespace eve
{
   // Regular overload
   constexpr auto trunc(value auto x)                          noexcept; // 1
 
   // Lanes masking
   constexpr auto trunc[conditional_expr auto c](value auto x) noexcept; // 2
   constexpr auto trunc[logical_value auto m](value auto x)    noexcept; // 2
 
   // Semantic options
   constexpr auto trunc[almost = tol](floating_value auto x)   noexcept; // 3
   constexpr auto trunc[almost](floating_value auto x)         noexcept; // 4
   constexpr auto trunc[raw](floating_value auto x)            noexcept; // 5
}

Parameters

• x :value argument.
• c: Conditional expression masking the operation.
• m: Logical value masking the operation.
• tol scalar_value tolerance.

Return value

1. The integral part of x with the same sign as x. The standard proposes 4 rounding modes namely: FE_TONEAREST, FE_DOWNWARD, FE_UPWARD, FE_TOWARDZERO. This function object implements the FE_TOWARDZERO version.
2. The operation is performed conditionnaly.
3. almost allows a fuzzy interpretation of ceil associated to a scalar tolerance.
   • with an integral value tol: computes the ceil of the previous nth representable value in the x type.
   • with a floating value tol: computes the ceil with a tolerance tol.
4. with no tolerance value, the call is equivalent to ceil[tolerance = 3*eps(as(x))(x)
5. Faster for floating inputs, but only correct if as an integer, the truncation that can be exactly represented in the associated integral type.

External references

• C++ standard reference