c function floor example

Write your own implementation of math's floor function, C

stackoverflow.com › questions › 41856771 › write-your-own-implementation-of-maths-floor-function-c

Both of your attempts have limitations:

If the double value is outside the range of the int type, converting to int is implementation defined.
If the double value is negative but integral, returning (int)num - 1 is incorrect.

Here is an (almost) portable version that tries to handle all cases:

double my_floor_2(double num) {
    if (num >= LLONG_MAX || num <= LLONG_MIN || num != num) {
        /* handle large values, infinities and nan */
        return num;
    }
    long long n = (long long)num;
    double d = (double)n;
    if (d == num || num >= 0)
        return d;
    else
        return d - 1;
}

It should be correct if type long long has more value bits than type double, which is the case on most modern systems.

Answer from chqrlie on Stack Overflow

TutorialsPoint

tutorialspoint.com › home › c_standard_library › c standard library: floor function

C Standard Library: floor Function

August 29, 2012 - Following is the syntax of the C library function floor() − ... This function returns the largest integral value not greater than x. Following is the basic C library example to see the demonstration of floor() function.

TechOnTheNet

techonthenet.com › c_language › standard_library_functions › math_h › floor.php

C Language: floor function (Floor)

In the C Language, the required ... floor of value */ result = floor(value); /* Display the result of the calculation */ printf("The floor of %f is %f\n", value, result); return 0; }...

Discussions

Write your own implementation of math's floor function, C - Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most. Learn more about Collectives ... Bring the best of human thought and AI automation together at your work. Explore Stack Internal ... I was thinking about the floor function available in math.h. More on stackoverflow.com

stackoverflow.com

Does anyone know how to create a floor function in c

Can you not just cast it to an int? float f; int i; f = 4.6; i = (int)f; edit : learned about the html editor More on reddit.com

r/AskProgramming

January 5, 2025

Compilation error; why can't gcc recognize the floor function here?

Have you tried gcc -lm option? More on reddit.com

r/C_Programming

August 23, 2021

My teacher keeps insisting that the whole part of a number is the same as the floor function. Is he right?

From Wikipedia : The floor function (or greatest integer function) is the function that takes as input a real number x, and gives as output the greatest integer less than or equal to x, denoted ⌊x⌋ or floor(x)... Historically, the floor of x has been–and still is–called the integral part or integer part of x, often denoted [x] (as well as a variety of other notations). However, the same term, integer part, is also used for truncation towards zero, which differs from the floor function for negative numbers. One general remark: in mathematics it is considered unwise to argue about definitions. As long as a person properly defines their notations and concepts, they are fine. Of course, if they use a different notation than everybody else, they may be considered weird, but it does not mean they made a mathematical mistake. Instead of arguing, ask a person for the source of their definition: a textbook, an encyclopedia, and so on. More on reddit.com

r/learnmath

April 4, 2024

Videos

02:00

YouTube

C Programming Math Library | Floor Function - YouTube

C Programming Tutorial - Ceil and Floor Functions - YouTube

January 3, 2022

07:52

YouTube

round(), ceil(), floor() and trunc() double rounding functions ...

August 17, 2021

05:15

YouTube

Learn C math functions in 5 minutes! 🧮 - YouTube

March 1, 2025

youtube.com

Round() / Trunc() / CEIL() Floor() Function in C Programming Part-1| ...

September 19, 2024

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GeeksforGeeks

geeksforgeeks.org › c language › c-floor-function

C floor() Function - GeeksforGeeks

July 7, 2024 - The floor(x) function takes a floating-point number x and returns the largest integer less than or equal to x. Internally, it checks the value of x and rounds it down to the nearest integer. If x is already an integer, it returns x itself.

Programiz

programiz.com › c-programming › library-function › math.h › floor

C floor() - C Standard Library

The function prototypes for the long double and float versions of the floor() function are: long double floorl(long double arg); float floorf(float arg); #include <stdio.h> #include <math.h> int main() { double num = -8.33; double result = floor(num); printf("Floor integer of %.2f = %.0f", ...

Tutorial Gateway

tutorialgateway.org › c-floor-function

C floor Function

April 5, 2025 - #include <stdio.h> #include <math.h> int main() { printf("\n The Floor Value of 0.75 = %.2f ", floor(0.75)); printf("\n The Floor Value of 12.25 = %.2f ", floor(12.25)); printf("\n The Floor Value of 152.50 = %.2f ", floor(152.50)); printf("\n ...

W3Schools

w3schools.com › c › ref_math_floor.php

C Math floor() Function

C Examples C Real-Life Examples ... ... printf("%f", floor(0.60)); printf("%f", floor(0.40)); printf("%f", floor(5)); printf("%f", floor(5.1)); printf("%f", floor(-5.1)); printf("%f", floor(-5.9)); Try it Yourself » · The floor() function rounds a number DOWN to the nearest integer...

Stack Overflow

stackoverflow.com › questions › 41856771 › write-your-own-implementation-of-maths-floor-function-c

Write your own implementation of math's floor function, C - Stack Overflow

Top answer

1 of 5

Both of your attempts have limitations:

If the double value is outside the range of the int type, converting to int is implementation defined.
If the double value is negative but integral, returning (int)num - 1 is incorrect.

Here is an (almost) portable version that tries to handle all cases:

double my_floor_2(double num) {
    if (num >= LLONG_MAX || num <= LLONG_MIN || num != num) {
        /* handle large values, infinities and nan */
        return num;
    }
    long long n = (long long)num;
    double d = (double)n;
    if (d == num || num >= 0)
        return d;
    else
        return d - 1;
}

It should be correct if type long long has more value bits than type double, which is the case on most modern systems.

2 of 5

No, you can't tackle it this way. The best way of writing your own implementation is to take the one from the C Standard Library on your platform. But note that might contain platform specific nuances so might not be portable.

The C Standard Library floor function is typically clever in that it doesn't work by taking a conversion to an integral type. If it did then you'd run the risk of signed integer overflow, the behaviour of which is undefined. (Note that the smallest possible range for an int is -32767 to +32767).

The precise implementation is also dependent on the floating point scheme used on your platform.

For a platform using IEEE754 floating point, and a long long type you could adopt this scheme:

If the magnitude of the number is greater than 2⁵³, return it (as it's already integral).
Else, cast to a 64-bit type (long long), and return it back.

Find elsewhere

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Microsoft Learn

learn.microsoft.com › en-us › cpp › c-runtime-library › reference › floor-floorf-floorl

floor, floorf, floorl | Microsoft Learn

October 3, 2025 - By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT. For more compatibility information, see Compatibility. // crt_floor.c // This example displays the largest integers // less than or equal to the floating-point values 2.8 // and -2.8.

Linux Hint

linuxhint.com › floor-function-in-c

Floor Function in C – Linux Hint

From the output screenshot, we all can see that the program is running seamlessly. Several additional variations of inputs were used for testing to get a better understanding of the floor function: Now, for this example, let’s try passing negative decimal values to our floor function.

Scaler

scaler.com › home › topics › floor() in c

floor() Function in C - Scaler Topics

June 16, 2024 - This function returns the nearest ... to it as an argument. For example, if we pass a floating point number 5.6677 to the floor() function, the return value will be 5 (an integer)....

W3Resource

w3resource.com › c-programming › math › c-floor.php

C floor() function

December 24, 2022 - The floor() function is used to calculate the largest integer that is less than or equal to x. ... Returns the floating-point result as a double value. ... The following example shows the usage of floor() function.

IncludeHelp

includehelp.com › c-programs › c-basic-programs-to-demonstrate-example-of-floor-and-ceil-functions.aspx

C program to demonstrate example of floor() and ceil() functions

June 24, 2020 - /* C program to demonstrate example of floor and ceil functions.*/ #include <stdio.h> #include <math.h> int main() { float val; float fVal,cVal; printf("Enter a float value: "); scanf("%f",&val); fVal=floor(val); cVal =ceil(val); printf("floor value:%f \nceil value:%f\n",fVal,cVal); return 0; }

Cppreference

en.cppreference.com › w › c › numeric › math › floor

floor, floorf, floorl - cppreference.com

May 23, 2024 - ... #include <math.h> #include <stdio.h> int main(void) { printf("floor(+2.7) = %+.1f\n", floor(2.7)); printf("floor(-2.7) = %+.1f\n", floor(-2.7)); printf("floor(-0.0) = %+.1f\n", floor(-0.0)); printf("floor(-Inf) = %+f\n", floor(-INFINITY)); } ... Retrieved from "https://en.cppreference....

Cplusplus

cplusplus.com › reference › cmath › floor

Floor

double floor (double x); float floor (float x);long double floor (long double x); double floor (T x); // additional overloads for integral types · Round down value · Rounds x downward, returning the largest integral value that is not greater than x. Header <tgmath.h> provides a type-generic ...

Aticleworld

aticleworld.com › home › floor function in c

floor function in C - Aticleworld

September 28, 2021 - If arg is ±0, it is returned, unmodified. If arg is NaN, NaN is returned. #include <math.h> #include <stdio.h> int main(void) { printf("floor(-0.0) = %+.1f\n", floor(-0.0)); printf("floor(-Inf) = %+f\n", floor(-INFINITY)); return 0; } ... Use of pow function in C language.

reddit.com › r/askprogramming › does anyone know how to create a floor function in c

r/AskProgramming on Reddit: Does anyone know how to create a floor function in c

January 5, 2025 -

I'm working on a project that doesn't use any c libraries and can't figure it out