ldexp(3)

✨ ldexp(3) ✨ — the manual page for ldexp, ldexpf, ldexpl 💖

okay bestie, welcome to the glow-up zone 🦋 this is the page about ldexp, ldexpf, and ldexpl — three little math-library icons that take a floating-point number and scale it by a power of two. no cap, it's giving "scientific notation but make it binary" and honestly? obsessed.

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🌸 NAME 🌸

ldexp, ldexpf, ldexpl — multiply floating-point number by integral power of 2 💅

📚 LIBRARY 📚

Math library (libm, -lm) — yes bestie, you have to link -lm. she does not come for free. 🎀

🫶 SYNOPSIS 🫶

#include <math.h>

double ldexp(double x, int e);
float ldexpf(float x, int e);
long double ldexpl(long double x, int e);

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

ldexpf(), ldexpl():
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

fr fr, if you're on an older glibc and these macros stress you out, that's normal. you're doing amazing sweetie 💜

💖 DESCRIPTION 💖

so the way that these functions work is: they return the result of multiplying the floating-point number x by 2 raised to the power e. that's it. that's the whole vibe. ✨

🔥 RETURN VALUE 🔥

• On success, these functions return x * (2^e). iconic behavior, no notes. 👑
• If e is zero, then x is returned. (she said "i'm not doing anything today" and honestly, same 🛋️)
• If x is a NaN, a NaN is returned. NaN in, NaN out, the circle of life 🌈
• If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. she keeps her sign, as she should 💅
• If the result underflows, a range error occurs, and zero is returned. 😭
• If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with a sign the same as x. she went TOO big and now she's HUGE 💀

😭 ERRORS 😭

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

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

🎀 ATTRIBUTES 🎀

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

• Interface: ldexp(), ldexpf(), ldexpl() — Attribute: Thread safety — Value: MT-Safe ✅

(translation: she is safe to share across threads, bestie, go forth and multithread 🧵✨)

⭐ STANDARDS ⭐

C11, POSIX.1-2008. certified, stamped, official. 💖

🌈 HISTORY 🌈

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89. she's been around, she's got lore 📜

👀 SEE ALSO 👀

frexp(3), modf(3), scalbln(3)

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and that's the whole page, bestie!! 🫶 this came to you via Linux man-pages 6.20, dated 2026-02-08. go multiply something by a power of two and slay 💅✨🌸