power of 2
double ldexp(double x, int exp);
float ldexpf(float x, int exp);
long double ldexpl(long double x, int exp);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
The ldexp() function returns the result of multiplying the floating-
point number x by 2 raised to the power exp.
On success, these functions return x * (2^exp).
If exp is zero, then x is returned.
If x is a NaN, a NaN is returned.
If x is positive infinity (negative infinity), positive infinity (nega-
tive infinity) is returned.
If the result underflows, a range error occurs, and zero is returned.
If the result overflows, a range error occurs, and the functions return
HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with a sign the same
See math_error(7) for information on how to determine whether an error
has occurred when calling these functions.
The following errors can occur:
Range error, overflow
errno is set to ERANGE. An overflow floating-point exception
(FE_OVERFLOW) is raised.
Range error, underflow
errno is set to ERANGE. An underflow floating-point exception
(FE_UNDERFLOW) is raised.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4,
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