c99 [ flag... ] file... –lm [ library... ] #include <math.h> double ldexp(double x, int exp);
float ldexpf(float x, int exp);
long double ldexpl(long double x, int exp);
These functions computes the quantity x * 2exp.
Upon successful completion, these functions return x multiplied by 2 raised to the power exp.
If these functions would cause overflow, a range error occurs and ldexp(), ldexpf(), and ldexpl() return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x), respectively.
If x is NaN, a NaN is returned.
If x is ±0 or ±Inf, x is returned.
If exp is 0, x is returned.
These functions will fail if:
The result overflows.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception is raised.
The ldexp() function sets errno to ERANGE if the result overflows.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
An application can also set errno to 0 before calling ldexp(). On return, if errno is non-zero, an error has occurred. The ldexpf() and ldexpl() functions do not set errno.
See attributes(5) for descriptions of the following attributes: