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.\" @(#)ieee.3 6.4 (Berkeley) 5/6/91
.Nd exponent manipulations
.Fn copysign "double x" "double y"
.Fn drem "double x" "double y"
.Fn scalb "double x" "int n"
These functions are required for, or recommended by the
754 for floating\-point arithmetic.
is the integer nearest the exact value of
.Fa x No / Fa y No \\*(Ba
the remainder is computed exactly and
.Pf \\*(Ba Fa r No \\*(Ba
.Pf \\*(Ba Fa y No \\*(Ba/2.
function returns the value 1 just when
.Pf \\*(Ba Ns Fa x Ns \\*(Ba
a signed integer converted to double\-precision floating\-point and so
.Pf \\*(Ba Ns Fa x Ns \\*(Ba2** Ns Fa n
(only on machines that conform to
.Pf \\*(Ba Fa x Ns \\*(Ba
lies between 0 and the Underflow Threshold.
.Fa x Ns \(**(2** Ns Fa n )
computed, for integer n, without first computing
to be invalid operations that produce a \*(Na.
generates a reserved operand fault. No \*(If
requires the latter to signal Division\-by\-Zero.
= 1.0 \- 2.0**31 = \-2,147,483,647.0.
And if the correct value of
it generates a reserved operand fault and sets the global variable
754 currently specifies that
.Fn logb "denormalized no."
.Fn logb "tiniest normalized no. > 0"
but the consensus has changed to the specification in the new
standard p854, namely that
.Bd -filled -offset indent
.Fn scalb \\*(Bax\\*(Ba \-logb(x)
Almost every program that assumes 754's specification will work
follows 854's specification instead.
else about the sign of a \*(Na. A \*(Na
reserved operand, but very
different in important details. Since the sign bit of a
reserved operand makes it look negative,
.Bd -filled -offset indent
.Fn copysign x "reserved operand"
should this return the reserved operand instead?