significand(3)

💖 significand(3) 💖

okay bestie, welcome to the manual page for significand, significandf, and significandl — direct from the weird little corner of libm where the IEEE 754 girlies hang out. it's <italic>Library Functions Manual</italic> energy and honestly? iconic.

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✨ NAME ✨

significand, significandf, significandl — get the mantissa of a floating-point number 🎀

📚 LIBRARY 📚

Math library — that's libm, and you link it with -lm (yes you have to, no it's not optional, i don't make the rules 💅)

🌸 SYNOPSIS 🌸

#include <math.h>

double significand(double x);
float significandf(float x);
long double significandl(long double x);

🦋 Feature Test Macro Requirements for glibc (peep feature_test_macros(7)) 🦋

significand(), significandf(), significandl():
    /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

so like. if you're on modern glibc you just need _DEFAULT_SOURCE, but if you're on the older stuff you're out here juggling _BSD_SOURCE or _SVID_SOURCE. the vibes are ancient but she works 💀

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👑 DESCRIPTION 👑

these functions hand you the mantissa of x, scaled all cute into the range [1, FLT_RADIX) 🫶

they are literally equivalent to:

scalb(x, (double) -ilogb(x))

and ngl, this function exists mainly for use in certain standardized tests for IEEE 754 conformance. she's not the main character of your app, she's the main character of the test suite ⭐

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💅 ATTRIBUTES 💅

for an explanation of the terms used here, go read attributes(7), k? 💜

• Interface:</bold> significand(), significandf(), significandl() — Attribute: Thread safety — Value: MT-Safe 🔥

so yeah, thread safe, no cap, you can call her from anywhere at once. periodt.

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🌈 STANDARDS 🌈

None. 😭 that's it, that's the whole standard.

significand() : BSD. (she's a BSD girlie, always has been 🧚)

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💀 HISTORY 💀

significand() : BSD. yeah. same energy as above. she's been around the BSD block since forever 🙈

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🍓 SEE ALSO 🍓

• ilogb(3)
• scalb(3)

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okay bestie that's the whole page!! this was Linux man-pages 6.20, dated 2026-02-08, and she's the significand(3) page — go scale something, drink water, and remember: your mantissa is always valid 💖✨🎀🦋

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