ldexp, ldexpf, or ldexpl Subroutine

Purpose

Loads exponent of a floating-point number.

Syntax

#include <math.h>
float ldexpf (x, exp)
float x;
int exp;

long double ldexpl (x, exp)
long double x;
int exp;

double ldexp (x, exp)
double  x;
int exp;

Description

The ldexpf, ldexpl, and ldexp subroutines compute the quantity x * 2^exp.

An application wishing to check for error situations should set the errno global variable to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. Upon return, if errno is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has occurred.

Parameters

Item	Description
x	Specifies the value to be computed.
exp	Specifies the exponent of 2.

Return Values

Upon successful completion, the ldexpf, ldexpl, and ldexp subroutines return x multiplied by 2, raised to the power exp.

If the ldexpf, ldexpl, or ldexp subroutines would cause overflow, a range error occurs and the ldexpf, ldexpl, and ldexp subroutines return ±HUGE_VALF, ±HUGE_VALL, and ±HUGE_VAL (according to the sign of x), respectively.

If the correct value would cause underflow, and is not representable, a range error may occur, and 0.0 is returned.

If x is NaN, a NaN is returned.

If x is ±0 or Inf, x is returned.

If exp is 0, x is returned.

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

Error Codes

If the result of the ldexp or ldexpl subroutine overflows, then +/- HUGE_VAL is returned, and the global variable errno is set to ERANGE.

If the result of the ldexp or ldexpl subroutine underflows, 0 is returned, and the errno global variable is set to a ERANGE value.