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'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH ldexp 3 2025-07-19 "Linux man-pages (unreleased)"
.SH NAME
ldexp, ldexpf, ldexpl \- multiply floating-point number by integral power of 2
.SH LIBRARY
Math library
.RI ( libm ,\~ \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double ldexp(double " x ", int " e );
.BI "float ldexpf(float " x ", int " e );
.BI "long double ldexpl(long double " x ", int " e );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR ldexpf (),
.BR ldexpl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions return the result of multiplying the floating-point number
.I x
by 2 raised to the power
.IR e .
.SH RETURN VALUE
On success, these functions return
.IR "x * (2\[ha]e)" .
.P
If
.I e
is zero, then
.I x
is returned.
.P
If
.I x
is a NaN,
a NaN is returned.
.P
If
.I x
is positive infinity (negative infinity),
positive infinity (negative infinity) is returned.
.P
If the result underflows,
a range error occurs,
and zero is returned.
.P
If the result overflows,
a range error occurs,
and the functions return
.BR HUGE_VAL ,
.BR HUGE_VALF ,
or
.BR HUGE_VALL ,
respectively, with a sign the same as
.IR x .
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.P
The following errors can occur:
.TP
Range error, overflow
.I errno
is set to
.BR ERANGE .
An overflow floating-point exception
.RB ( FE_OVERFLOW )
is raised.
.TP
Range error, underflow
.I errno
is set to
.BR ERANGE .
An underflow floating-point exception
.RB ( FE_UNDERFLOW )
is raised.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR ldexp (),
.BR ldexpf (),
.BR ldexpl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR frexp (3),
.BR modf (3),
.BR scalbln (3)
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