hypot(3)

💖 hypot(3) — the "how far is it tho" math bestie ✨

okay so bestie, welcome to hypot(3) from the Library Functions Manual 🎀 this is the math-girlie page and honestly? she ate. no cap.

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🌸 NAME 🌸

hypot, hypotf, hypotl — the Euclidean distance function 💅

📚 LIBRARY 📚

Math library (libm, -lm) — yeah you gotta link the math lib, she doesn't come free 🫶

✨ SYNOPSIS ✨

#include <math.h>

double hypot(double x, double y);
float hypotf(float x, float y);
long double hypotl(long double x, long double y);

🧚 Feature Test Macro Requirements for glibc (iykyk, see feature_test_macros(7))

hypot():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
    || _XOPEN_SOURCE
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

hypotf(), hypotl():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

bestie note: the difference between those two blocks is literally just the _XOPEN_SOURCE line and it's ONLY in hypot(). not me double-checking that five times 🙈 anyway, copy them exactly, they're load-bearing.

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🌈 DESCRIPTION 🌈

These functions return sqrt(x*x+y*y). 🧮✨

So basically: it's the length of the hypotenuse of a right-angled triangle whose sides are x and y long. OR, lowkey the same thing, it's the distance from the point (x,y) to the origin. same vibe, different outfit 💅

The calculation is performed without undue overflow or underflow during the intermediate steps of the calculation. <- this is the whole reason hypot exists and isn't just you typing sqrt(x*x+y*y) by hand, bestie. she's careful. she's got main character energy. 👑

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🦋 RETURN VALUE 🦋

On success, these functions return the length of the hypotenuse of a right-angled triangle with sides of length x and y. easy, iconic, no notes ✨

If x or y is an infinity, positive infinity is returned. ♾️

If x or y is a NaN, and the other argument is not an infinity, a NaN is returned. 🫠

If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively. 😭

If both arguments are subnormal, and the result is subnormal, a range error occurs, and the correct result is returned. yes bestie, error AND correct answer at the same time, she's multitasking 💀

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💀 ERRORS 💀

See math_error(7) for the deets on how to figure out whether an error actually happened when you called these functions.

The following errors can occur:

• Range error: result overflow — errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised. 🔥
• Range error: result underflow — An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno for this case. not me checking errno for no reason 🙈

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👑 ATTRIBUTES 👑

For an explanation of the terms used in this section, see attributes(7).

• Interface: hypot(), hypotf(), hypotl()
• Attribute: Thread safety
• Value: MT-Safe 🔒 (she's safe to use across threads, periodt)

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⭐ STANDARDS ⭐

C11, POSIX.1-2008.

🎀 HISTORY 🎀

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD. yes she's old money AND new money 💜

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💖 SEE ALSO 💖

cabs(3), sqrt(3)

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okay that's the whole page bestie, go forth and compute your distances the safe way 🌸🦋✨

ciao for now, and remember this was served fresh from Linux man-pages 6.20, dated 2026-02-08 — hypot(3), signing off 💅🎀🍓