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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 $
34 .\" $DragonFly: src/lib/libm/common_source/Attic/ieee.3,v 1.2 2003/06/17 04:26:50 dillon Exp $
45 .Nd "IEEE 754 floating point support
51 .Fn copysign "double x" "double y"
53 .Fn drem "double x" "double y"
59 .Fn scalb "double x" "int n"
61 These functions are required for, or recommended by the
64 754 for floating\-point arithmetic.
71 with its sign changed to
85 is the integer nearest the exact value of
93 .Fa x No / Fa y No \\*(Ba
100 the remainder is computed exactly and
102 .Pf \\*(Ba Fa r No \\*(Ba
106 .Pf \\*(Ba Fa y No \\*(Ba/2 .
116 function returns the value 1 just when
123 .Pf \\*(Ba Ns Fa x Ns \\*(Ba
136 a signed integer converted to double\-precision floating\-point and so
139 .Pf \\*(Ba Ns Fa x Ns \\*(Ba2** Ns Fa n
144 (only on machines that conform to
147 .Pf \\*(Ba Fa x Ns \\*(Ba
151 lies between 0 and the Underflow Threshold.
158 .Fa x Ns \(**(2** Ns Fa n )
159 computed, for integer n, without first computing
169 to be invalid operations that produce a \*(Na.
173 generates a reserved operand fault. No \*(If
184 requires the latter to signal Division\-by\-Zero.
188 = 1.0 \- 2.0**31 = \-2,147,483,647.0.
189 And if the correct value of
193 it generates a reserved operand fault and sets the global variable
204 functions appeared in
215 .Va errno No = Er EDOM ?
221 754 currently specifies that
222 .Fn logb "denormalized no.\&"
224 .Fn logb "tiniest normalized no. > 0"
225 but the consensus has changed to the specification in the new
228 standard p854, namely that
231 .Bd -ragged -offset indent
233 .Fn scalb \\*(Bax\\*(Ba \-logb(x)
241 for every x except 0,
244 Almost every program that assumes 754's specification will work
247 follows 854's specification instead.
251 .Fn copysign x \\*(Na)
255 else about the sign of a \*(Na. A \*(Na
260 similar in spirit to the
262 reserved operand, but very
263 different in important details. Since the sign bit of a
264 reserved operand makes it look negative,
265 .Bd -ragged -offset indent
266 .Fn copysign x "reserved operand"
271 should this return the reserved operand instead?