# ldexp(3) — Linux manual page

```ldexp(3)                Library Functions Manual                ldexp(3)
```

## NAME         top

```       ldexp, ldexpf, ldexpl - multiply floating-point number by
integral power of 2
```

## LIBRARY         top

```       Math library (libm, -lm)
```

## SYNOPSIS         top

```       #include <math.h>

double ldexp(double x, int exp);
float ldexpf(float x, int exp);
long double ldexpl(long double x, int exp);

Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):

ldexpf(), ldexpl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION         top

```       These functions return the result of multiplying the floating-
point number x by 2 raised to the power exp.
```

## RETURN VALUE         top

```       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
(negative 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 as x.
```

## ERRORS         top

```       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.
```

## ATTRIBUTES         top

```       For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface                           │ Attribute     │ Value   │
├─────────────────────────────────────┼───────────────┼─────────┤
│ ldexp(), ldexpf(), ldexpl()         │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## STANDARDS         top

```       C11, POSIX.1-2008.
```

## HISTORY         top

```       C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89.
```

```       frexp(3), modf(3), scalbln(3)