# std::floor, std::floorf, std::floorl

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< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
| (1) |
float floor ( float num ); double floor ( double num ); long double floor ( long double num ); |  | (until C++23)
constexpr /* floating-point-type */ floor ( /* floating-point-type */ num ); |  | (since C++23)
float floorf( float num ); | (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 > double floor ( Integer num ); | (A) | (constexpr since C++23)

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 treated as double. | (since C++11)

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

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