std::floor

C++

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Common mathematical functions

Functions
Basic operations
abs(int)labsllabsimaxabs (C++11) abs(float)fabs divldivlldivimaxdiv (C++11) fmod	remainder (C++11) remquo (C++11) fma (C++11) fmax (C++11) fmin (C++11) fdim (C++11) nannanfnanl (C++11)(C++11)(C++11)
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erf (C++11) erfc (C++11)	lgamma (C++11) tgamma (C++11)
Nearest integer floating point operations
ceil floor roundlroundllround (C++11)(C++11)(C++11)	trunc (C++11) nearbyint (C++11) rintlrintllrint (C++11)(C++11)(C++11)
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ldexp scalbnscalbln (C++11)(C++11) ilogb (C++11) logb (C++11)	frexp modf nextafternexttoward (C++11)(C++11) copysign (C++11)
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fpclassify (C++11) isfinite (C++11) isinf (C++11) isnan (C++11) isnormal (C++11) signbit (C++11)	isgreater (C++11) isgreaterequal (C++11) isless (C++11) islessequal (C++11) islessgreater (C++11) isunordered (C++11)
Macro constants
HUGE_VALFHUGE_VALHUGE_VALL (C++11)(C++11) INFINITY (C++11) NAN (C++11) math_errhandlingMATH_ERRNOMATH_ERREXCEPT (C++11)	FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C++11)(C++11)(C++11)(C++11)(C++11)

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

1-3) Computes the largest integer value not greater 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 largest integer value not greater than arg, that is arg, is returned.

Return value

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	nearest integer not less than the given value (function)
trunc (C++11)	nearest integer not greater in magnitude than the given value (function)
roundlroundllround (C++11)(C++11)(C++11)	nearest integer, rounding away from zero in halfway cases (function)