Open System Services Library Calls Reference Manual (G06.29+, H06.08+, J06.03+)

ldexp(3) OSS Library Calls Reference Manual
NAME
ldexp - Multiplies a floating-point number by a power of 2
LIBRARY
G-series native Guardian processes: $SYSTEM.SYSnn.ZCRESRL
G-series native OSS processes: /G/system/sysnn/zcresrl
H-series and J-series native Guardian processes: $SYSTEM.ZDLLnnn.ZCREDLL
32-bit H-series and J-series OSS processes: /G/system/zdllnnn/zcredll
64-bit H-series and J-series OSS processes: /G/system/zdllnnn/ycredll
SYNOPSIS
#include <math.h>
double ldexp(
double value,
int exp
);
PARAMETERS
value Specifies the value to be multiplied by a power of 2.
exp Specifies the exponent for 2.
DESCRIPTION
Every nonzero number can be written uniquely as x times 2 raised to the power n, where the
mantissa (fraction), x, is in the range 0.5 ≤ | x | < 1.0, and the exponent, n, is an integer.
The ldexp( ) function multiplies the floating-point number value by an integral power of 2.
NOTES
This function supports both IEEE Std 754-1985 floating-point and Tandem floating-point values
in the native environment. IEEE values can include NaN and infinity, and the sign of 0.0 (zero)
can be either positive or negative. Refer to the fp_class(3) reference page for a description of
IEEE value classes.
Guardian functions are available to convert between floating-point formats. Refer to the Guar-
dian Programmer’s Guide for a discussion of floating-point conversions.
RETURN VALUES
Upon successful completion, the ldexp( ) function returns a double value equal to value times 2
to the power exp.
For IEEE floating-point values, if the value of value is NaN, NaN is returned. If the value of
value is positive or negative infinity, the value of value is returned.
If ldexp( ) would cause overflow, positive or negative HUGE_VAL is returned (according to the
sign of value) and errno is set to [ERANGE]. If ldexp( ) would cause underflow, a value of 0.0
(zero) is returned and errno is set to [ERANGE].
ERRORS
If any of the following conditions occurs, the ldexp( ) function sets errno to the corresponding
value:
[ERANGE] The value to be returned would cause an overflow or underflow.
RELATED INFORMATION
Functions: fp_class(3), frexp(3), isnan(3), modf(3).
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