isgreater(3)

💖 isgreater(3) — floating-point relational tests, but make it NaN-safe 💖

okay bestie, so this is a page from the Library Functions Manual, and it's about a lil family of macros that do comparisons without having a meltdown when NaN shows up 💅

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✨ NAME ✨

isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered — floating-point relational tests without exception for NaN 🦋

📚 LIBRARY 📚

Math library (libm, -lm) — yeah you gotta link it, that's just the vibe.

🌸 SYNOPSIS 🌸

#include <math.h>

int isgreater(x, y);
int isgreaterequal(x, y);
int isless(x, y);
int islessequal(x, y);
int islessgreater(x, y);
int isunordered(x, y);

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

All functions described here:

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

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👑 DESCRIPTION 👑

ok so here's the tea ☕ — the normal relational operations (like <, that's "less than") literally fail if one of the operands is NaN. and not in a cute way, it causes an exception. so to dodge all that drama, C99 defines the macros listed below. era-defining honestly ✨

these macros are guaranteed to evaluate their arguments only once. and the arguments must be of real floating-point type. quick PSA: do NOT pass integer values as arguments to these macros, because the arguments will not be promoted to real-floating types. not me warning you twice, but like, i'm warning you twice 🙈

• isgreater() — figures out (x) > (y) without an exception if x or y is NaN.
• isgreaterequal() — figures out (x) >= (y) without an exception if x or y is NaN.
• isless() — figures out (x) < (y) without an exception if x or y is NaN.
• islessequal() — figures out (x) <= (y) without an exception if x or y is NaN.
• islessgreater() — figures out (x) < (y) || (x) > (y) without an exception if x or y is NaN. ⚠️ and this macro is not equivalent to x != y, because that expression is true if x or y is NaN. so like, don't try that shortcut bestie, it's giving wrong answers 💀
• isunordered() — figures out whether its arguments are unordered, which is just a fancy way of saying: is at least one of the arguments a NaN? 🧚

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💫 RETURN VALUE 💫

every macro except isunordered() returns the result of the relational comparison. and those macros return 0 if either argument is a NaN. (yeah, NaN just kills the whole comparison, that's the point.)

isunordered() returns 1 if x or y is NaN, and 0 otherwise. simple. iconic. slay 💅

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💀 ERRORS 💀

No errors occur. literally none. that's the entire flex of this page, no cap. ✨

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🌈 ATTRIBUTES 🌈

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

• Interface: isgreater(), isgreaterequal(), isless(), islessequal(), islessgreater(), isunordered()
  • Attribute: Thread safety
  • Value: MT-Safe 👑

so yeah, all of them are MT-Safe. go wild with your threads, it's fine 🫶

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🦋 VERSIONS 🦋

not all hardware supports these functions, and where hardware support isn't provided, they'll be emulated by macros instead. and that comes with a performance penalty 😭.

don't use these functions if NaN is of no concern for you. fr fr, if you don't care about NaN, you're just paying the vibe tax for nothing.

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⭐ STANDARDS ⭐

C11, POSIX.1-2008.

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🌸 HISTORY 🌸

POSIX.1-2001, C99.

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🎀 SEE ALSO 🎀

• fpclassify(3)
• isnan(3)

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and that's the whole page, bestie! this was isgreater(3) from Linux man-pages 6.20, dated 2026-02-08 — go forth and compare floats without fear of exceptions 💖✨🦋💅