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32 .\" @(#)ieee.3 8.1 (Berkeley) 6/4/93
33 .\" $FreeBSD: src/lib/libm/common_source/ieee.3,v 1.4.2.5 2001/08/17 15:43:05 ru Exp $
44 .Nd "IEEE 754 floating point support
50 .Fn copysign "double x" "double y"
52 .Fn drem "double x" "double y"
58 .Fn scalb "double x" "int n"
60 These functions are required for, or recommended by the
63 754 for floating\-point arithmetic.
70 with its sign changed to
84 is the integer nearest the exact value of
92 .Fa x No / Fa y No \\*(Ba
99 the remainder is computed exactly and
101 .Pf \\*(Ba Fa r No \\*(Ba
105 .Pf \\*(Ba Fa y No \\*(Ba/2 .
115 function returns the value 1 just when
122 .Pf \\*(Ba Ns Fa x Ns \\*(Ba
135 a signed integer converted to double\-precision floating\-point and so
138 .Pf \\*(Ba Ns Fa x Ns \\*(Ba2** Ns Fa n
143 (only on machines that conform to
146 .Pf \\*(Ba Fa x Ns \\*(Ba
150 lies between 0 and the Underflow Threshold.
157 .Fa x Ns \(**(2** Ns Fa n )
158 computed, for integer n, without first computing
168 to be invalid operations that produce a \*(Na.
172 generates a reserved operand fault. No \*(If
183 requires the latter to signal Division\-by\-Zero.
187 = 1.0 \- 2.0**31 = \-2,147,483,647.0.
188 And if the correct value of
192 it generates a reserved operand fault and sets the global variable
203 functions appeared in
214 .Va errno No = Er EDOM ?
220 754 currently specifies that
221 .Fn logb "denormalized no.\&"
223 .Fn logb "tiniest normalized no. > 0"
224 but the consensus has changed to the specification in the new
227 standard p854, namely that
230 .Bd -ragged -offset indent
232 .Fn scalb \\*(Bax\\*(Ba \-logb(x)
240 for every x except 0,
243 Almost every program that assumes 754's specification will work
246 follows 854's specification instead.
250 .Fn copysign x \\*(Na)
254 else about the sign of a \*(Na. A \*(Na
259 similar in spirit to the
261 reserved operand, but very
262 different in important details. Since the sign bit of a
263 reserved operand makes it look negative,
264 .Bd -ragged -offset indent
265 .Fn copysign x "reserved operand"
270 should this return the reserved operand instead?