NAME¶

std::floor,std::floorf,std::floorl - std::floor,std::floorf,std::floorl

Synopsis¶

Defined in header <cmath>
float floor ( float arg ); (1) (constexpr since C++23)
float floorf( float arg ); (2) (since C++11)
(constexpr since C++23)
double floor ( double arg ); (3) (constexpr since C++23)
long double floor ( long double arg ); (4) (constexpr since C++23)
long double floorl( long double arg ); (5) (since C++11)
(constexpr since C++23)
double floor ( IntegralType arg ); (6) (since C++11)
(constexpr since C++23)

1-5) Computes the largest integer value not greater than arg.
6) A set of overloads or a function template accepting an argument of any integral
type. Equivalent to (3) (the argument is cast to double).

Parameters¶

arg - floating point value

Return value¶

If no errors occur, the largest integer value not greater than arg, that is
⌊arg⌋, is returned.

Return value¶

math-floor.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 rounding 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.

Example¶

// Run this code

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

Output:¶

floor(+2.7) = 2.000000
floor(-2.7) = -3.000000
floor(-0.0) = -0.000000
floor(-Inf) = -inf

See also¶

ceil
ceilf nearest integer not less than the given value
ceill (function)
(C++11)
(C++11)
trunc
truncf
truncl nearest integer not greater in magnitude than the given value
(C++11) (function)
(C++11)
(C++11)
round
roundf
roundl
lround
lroundf
lroundl
llround
llroundf
llroundl nearest integer, rounding away from zero in halfway cases
(C++11) (function)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)