[ Bottom of Page | Previous Page | Next Page | Contents | Index | Library Home | Legal | Search ]

# Technical Reference: Base Operating System and Extensions, Volume 1

## 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 * 2exp.

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

 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.

### Related Information

math.h in AIX 5L Version 5.2 Files Reference.

[ Top of Page | Previous Page | Next Page | Contents | Index | Library Home | Legal | Search ]