LDEXP(3P)

🦋 PROLOG 🦋

ok so real talk bestie, this manual page is part of the POSIX Programmer's Manual — the Linux implementation of this interface may differ (so go peek at the corresponding Linux manual page for the tea on Linux behavior), or honestly the interface might not even be implemented on Linux at all. 💀

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✨ NAME ✨

ldexp, ldexpf, ldexpl — load exponent of a floating-point number 🎀

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🌸 SYNOPSIS 🌸

#include <math.h>

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

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💖 DESCRIPTION 💖

So the functionality described on this reference page is aligned with the ISO C standard. If there's any conflict between what's written here and the ISO C standard, that's not intentional, okay? This volume of POSIX.1‐2017 defers to the ISO C standard. periodt. 👑

These functions shall compute the quantity x * 2exp.

An application that wants to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. Then on return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero — congrats, an error has occurred. 😭

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🔥 RETURN VALUE 🔥

Upon successful completion, these functions shall return x multiplied by 2, raised to the power exp. slay.

If these functions would cause overflow, a range error shall occur and ldexp(), ldexpf(), and ldexpl() shall return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x), respectively. big yikes but okay.

If the correct value would cause underflow, and is not representable, a range error may occur, and ldexp(), ldexpf(), and ldexpl() shall return 0.0, or (if IEC 60559 Floating-Point is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

If x is NaN, a NaN shall be returned. 🫥

If x is ±0 or ±Inf, x shall be returned.

If exp is 0, x shall be returned.

If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

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😤 ERRORS 😤

These functions shall fail if:

• Range Error — The result overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

These functions may fail if:

• Range Error — The result underflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

ngl the following sections are informative. so like, cute bonus content, not the main character. 💅

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🧚 EXAMPLES 🧚

None. literally nothing. the void. 🙈

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💜 APPLICATION USAGE 💜

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero. no cap.

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⭐ RATIONALE ⭐

None.

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🌈 FUTURE DIRECTIONS 🌈

None.

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🎀 SEE ALSO 🎀

• feclearexcept()
• fetestexcept()
• frexp()
• isnan()

The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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okay bestie that's the whole page, ily, go multiply some stuff by 2^exp responsibly 🫶

this iconic lil page came to you from IEEE/The Open Group, dated 2017, and it lives in the LDEXP(3P) section of the POSIX Programmer's Manual ✨