NAME¶

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

Synopsis¶

Defined in header <cmath>
float floor ( float num );

double floor ( double num ); (until C++23)

long double floor ( long double num );
constexpr /* floating-point-type */ (since C++23)
floor ( /* floating-point-type */ num );
float floorf( float num ); (1) (2) (since C++11)
(constexpr since C++23)
long double floorl( long double num ); (3) (since C++11)
(constexpr since C++23)
Additional overloads (since C++11)
Defined in header <cmath>
template< class Integer > (A) (constexpr since C++23)
double floor ( Integer num );

1-3) Computes the largest integer value not greater than num.
The library provides overloads of std::floor for all cv-unqualified floating-point
types as the type of the parameter.
(since C++23)

A) Additional overloads are provided for all integer types, which are (since C++11)
treated as double.

Parameters¶

num - floating-point or integer value

Return value¶

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

Return value¶

math-floor.svg
num

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 num is ±∞, it is returned, unmodified.
* If num is ±0, it is returned, unmodified.
* If num 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.

The additional overloads are not required to be provided exactly as (A). They only
need to be sufficient to ensure that for their argument num of integer type,
std::floor(num) has the same effect as std::floor(static_cast<double>(num)).

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)
C documentation for
floor