std::floor,...std::floorl(3)

🌸 std::floor, std::floorf, std::floorl 💅

okay so bestie, this is the <cmath> page for the floor family — <cmath> version, C++ Standard Library vibes. and honestly? it's giving "round down and slay." let's get into it ✨

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🎀 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 );

so like, what do these actually do 👀

• 1-3) Computes the largest integer value not greater than num. that's it. that's the whole job. floor goes down 🦋
• Since C++23, the library provides overloads of std::floor for all cv-unqualified floating-point types as the type of the parameter.
• A) Additional overloads are provided for all integer types (since C++11), and those get treated as double.

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💖 PARAMETERS 💖

• num — a floating-point or integer value. that's the input, bestie 🫶

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👑 RETURN VALUE 👑

If no errors occur, you get back the largest integer value not greater than num, which is to say ⌊num⌋. periodt.

(the original page has a little picture here, math-floor.svg, showing num on the number line. imagine a cute lil staircase. that's the vibe 🎀)

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🔥 ERROR HANDLING 🔥

Errors are reported as specified in math_errhandling. (iykyk)

If the implementation supports IEEE floating-point arithmetic (IEC 60559), then:

• The current rounding mode has no effect. none. zero. it does not care 💀
• If num is ±∞, it is returned, unmodified.
• If num is ±0, it is returned, unmodified.
• If num is NaN, NaN is returned.

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✨ NOTES ✨

• FE_INEXACT may (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. so like, watch out when you shove it into an int, no cap.
• 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)). same energy, different implementation, we love flexible queens 💅

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🧚 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 how -2.7 becomes -3.000000? floor goes down, always down, and -0.0 keeps its whole sign situation. iconic behavior honestly 😭

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🦋 SEE ALSO 🦋

• ceil, ceilf, ceill — nearest integer not less than the given value (function, C++11 ×2)
• trunc, truncf, truncl — nearest integer not greater in magnitude than the given value (function, C++11)
• round, roundf, roundl, lround, lroundf, lroundl, llround, llroundf, llroundl — nearest integer, rounding away from zero in halfway cases (function, C++11 ×9)
• C documentation for floor — for the C girlies 🍓

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💜 and that's the whole page, bestie! this one's from http://cppreference.com, dated 2024.06.10, and it's part of the C++ Standard Library manual, section std::floor,...std::floorl(3). go forth and round down. slay ✨🎀