| '\" et |
| .TH LDEXP "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual" |
| .SH PROLOG |
| This manual page is part of the POSIX Programmer's Manual. |
| The Linux implementation of this interface may differ (consult |
| the corresponding Linux manual page for details of Linux behavior), |
| or the interface may not be implemented on Linux. |
| |
| .SH NAME |
| ldexp, |
| ldexpf, |
| ldexpl |
| \(em load exponent of a floating-point number |
| .SH SYNOPSIS |
| .LP |
| .nf |
| #include <math.h> |
| .P |
| double ldexp(double \fIx\fP, int \fIexp\fP); |
| float ldexpf(float \fIx\fP, int \fIexp\fP); |
| long double ldexpl(long double \fIx\fP, int \fIexp\fP); |
| .fi |
| .SH DESCRIPTION |
| The functionality described on this reference page is aligned with the |
| ISO\ C standard. Any conflict between the requirements described here and the |
| ISO\ C standard is unintentional. This volume of POSIX.1\(hy2008 defers to the ISO\ C standard. |
| .P |
| These functions shall compute the quantity |
| \fIx\fR\ *\ 2\u\s-3\fIexp\fR\s+3\d. |
| .P |
| An application wishing to check for error situations should set |
| .IR errno |
| to zero and call |
| .IR feclearexcept (FE_ALL_EXCEPT) |
| before calling these functions. On return, if |
| .IR errno |
| is non-zero or \fIfetestexcept\fR(FE_INVALID | FE_DIVBYZERO | |
| FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. |
| .SH "RETURN VALUE" |
| Upon successful completion, these functions shall return |
| .IR x |
| multiplied by 2, raised to the power |
| .IR exp . |
| .P |
| If these functions would cause overflow, a range error shall occur and |
| \fIldexp\fR(), |
| \fIldexpf\fR(), |
| and |
| \fIldexpl\fR() |
| shall return \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL (according |
| to the sign of |
| .IR x ), |
| respectively. |
| .P |
| If the correct value would cause underflow, |
| and is not representable, |
| a range error may occur, and |
| \fIldexp\fR(), |
| \fIldexpf\fR(), |
| and |
| \fIldexpl\fR() |
| 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. |
| .P |
| If |
| .IR x |
| is NaN, a NaN shall be returned. |
| .P |
| If |
| .IR x |
| is \(+-0 or \(+-Inf, |
| .IR x |
| shall be returned. |
| .P |
| If |
| .IR exp |
| is 0, |
| .IR x |
| shall be returned. |
| .P |
| If the correct value would cause underflow, and is representable, a |
| range error may occur and the correct value shall be returned. |
| .SH ERRORS |
| These functions shall fail if: |
| .IP "Range\ Error" 12 |
| The result overflows. |
| .RS 12 |
| .P |
| If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is |
| non-zero, then |
| .IR errno |
| shall be set to |
| .BR [ERANGE] . |
| If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is |
| non-zero, then the overflow floating-point exception shall be raised. |
| .RE |
| .P |
| These functions may fail if: |
| .IP "Range\ Error" 12 |
| The result underflows. |
| .RS 12 |
| .P |
| If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is |
| non-zero, then |
| .IR errno |
| shall be set to |
| .BR [ERANGE] . |
| If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is |
| non-zero, then the underflow floating-point exception shall be raised. |
| .RE |
| .LP |
| .IR "The following sections are informative." |
| .SH EXAMPLES |
| None. |
| .SH "APPLICATION USAGE" |
| On error, the expressions (\fImath_errhandling\fR & MATH_ERRNO) and |
| (\fImath_errhandling\fR & MATH_ERREXCEPT) are independent of each |
| other, but at least one of them must be non-zero. |
| .SH RATIONALE |
| None. |
| .SH "FUTURE DIRECTIONS" |
| None. |
| .SH "SEE ALSO" |
| .IR "\fIfeclearexcept\fR\^(\|)", |
| .IR "\fIfetestexcept\fR\^(\|)", |
| .IR "\fIfrexp\fR\^(\|)", |
| .IR "\fIisnan\fR\^(\|)" |
| .P |
| The Base Definitions volume of POSIX.1\(hy2008, |
| .IR "Section 4.19" ", " "Treatment of Error Conditions for Mathematical Functions", |
| .IR "\fB<math.h>\fP" |
| .SH COPYRIGHT |
| Portions of this text are reprinted and reproduced in electronic form |
| from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology |
| -- Portable Operating System Interface (POSIX), The Open Group Base |
| Specifications Issue 7, Copyright (C) 2013 by the Institute of |
| Electrical and Electronics Engineers, Inc and The Open Group. |
| (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 . |