HP-UX Reference (11i v1 05/09) - 3 Library Functions N-Z (vol 7)

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scalb(3M) scalb(3M)

NAME

scalb() - scale exponent of a radix-independent ﬂoating-point number

SYNOPSIS

#include <math.h>

double scalb(double x, double y);

DESCRIPTION

The scalb() function returns x ∗ r

, where r is the radix of the machine’s ﬂoating-point arithmetic.

When r is 2 (as it is on all PA-RISC systems),

scalb() is equivalent to ldexp().

The

scalb() function is recommended by the IEEE-754 standard for ﬂoating-point arithmetic. The

ISO/ANSI C committee has approved the

scalb() function for inclusion in the C9X draft standard.

To use this functions, compile either with the default

-Ae option or with the -Aa and -D_HPUX_SOURCE

options. Make sure your program includes <

math.h>. Link in the math library by specifying -lm on the

compiler or linker command line.

RETURN VALUE

Upon successful completion, the

scalb() function returns x ∗ r

scalb(-x, y) and -scalb(x, y) are equivalent.

If y is nonintegral, scalb() returns a NaN.

If y is ±zero, scalb() returns x.

If x is +zero and y is +INFINITY,

scalb() returns a NaN and raises the invalid exception.

If x is +zero and y is an integer less than +INFINITY,

scalb() returns +zero.

If x is +INFINITY and y is an integer greater than -INFINITY,

scalb() returns +INFINITY.

If x is ﬁnite and positive-signed and y is -INFINITY,

scalb() returns +zero.

If x is positive and y is +INFINITY,

scalb() returns +INFINITY.

If x is +INFINITY and y is -INFINITY,

scalb() returns a NaN.

If x or y is NaN,

scalb() returns a NaN.

If the correct value after rounding would be smaller in magnitude than MINDOUBLE, scalb() returns

zero.

If the correct value would overﬂow,

scalb() returns ±HUGE_VAL (according to the sign of x) and sets

errno to [ERANGE].

ERRORS

If scalb() fails, errno is set to the following value.

[ERANGE] The correct value would overﬂow.