std::trunc,std::truncf,std::truncl (3) - Linux Man Pages

std::trunc,std::truncf,std::truncl: std::trunc,std::truncf,std::truncl

NAME

std::trunc,std::truncf,std::truncl - std::trunc,std::truncf,std::truncl

Synopsis


Defined in header <cmath>
float trunc ( float arg ); (1) (since C++11)
float truncf( float arg );
double trunc ( double arg ); (2) (since C++11)
long double trunc ( long double arg ); (3) (since C++11)
long double truncl( long double arg );
double trunc ( IntegralType arg ); (4) (since C++11)


1-3) Computes the nearest integer not greater in magnitude than arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).

Parameters


arg - floating point value

Return value


If no errors occur, the nearest integer value not greater in magnitude than arg (in other words, arg rounded towards zero) is returned.

Return value


 math-trunc.svg
Argument

Error handling


Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),


* The current rounding_mode has no effect.
* If arg is ±∞, it is returned, unmodified
* If arg is ±0, it is returned, unmodified
* If arg is NaN, NaN is returned

Notes


FE_INEXACT may be (but isn't required to be) raised when truncating a non-integer finite value.
The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (including std::intmax_t), when stored in an integer variable.
The implicit_conversion from floating-point to integral types also rounds towards zero, but is limited to the values that can be represented by the target type.

Example


// Run this code


  #include <cmath>
  #include <iostream>
  int main()
  {
      std::cout << std::fixed
                << "trunc(+2.7) = " << std::trunc(+2.7) << '\n'
                << "trunc(-2.9) = " << std::trunc(-2.9) << '\n'
                << "trunc(-0.0) = " << std::trunc(-0.0) << '\n'
                << "trunc(-Inf) = " << std::trunc(-INFINITY) << '\n';
  }

Possible output:


  trunc(+2.7) = 2.000000
  trunc(-2.9) = -2.000000
  trunc(-0.0) = -0.000000
  trunc(-Inf) = -inf

See also


floor
floorf
floorl nearest integer not greater than the given value
         (function)


(C++11)
(C++11)


ceil
ceilf
ceill nearest integer not less than the given value
         (function)


(C++11)
(C++11)


round
roundf
roundl
lround
lroundf
lroundl
llround
llroundf
llroundl nearest integer, rounding away from zero in halfway cases
         (function)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)