.TH ieee 3m RISC.ds nn \fINaN\fR.SH Namecopysign, drem, finite, logb, scalb \- copysign, remainder,exponent manipulations.SH Syntax.nf.B #include <math.h>.PP.B double copysign(x,y).B double x,y;.PP.B double drem(x,y).B double x,y;.PP.B int finite(x).B double x;.PP.B double logb(x).B double x;.PP.B double scalb(x,n).B double x;.B int n;.fi.SH DescriptionThese functions are required, or recommended by the IEEE standard754 for floating\-point arithmetic..PPThe .PN copysignfunction returns x with its sign changed to y's..PPThe .PN drem(x,y)function returns the remainder r := x \- n\(**ywhere n is the integer nearest the exact value of x/y.  Additionallyif |\|n\|\-\|x/y|\|=\|1/2, then n is even.  Consequentlythe remainder is computed exactly and |\|r| \(<= |\|y|/2.  Notethat .PN drem(x,0) is the exception (see Diagnostics)..PP.nf.ta \w'Finite(x)'u+1n +\w'= 0 otherwise'u+1n.if n \Finite(x)	= 1 just when \-infinity < x < +infinity,.if t \Finite(x)	= 1 just when \-\(if < x < +\(if,.if n \	= 0 otherwise	(when |\|x| = infinity or x is \*(nn).if t \	= 0 otherwise	(when |\|x| = \(if or x is \*(nn).ta.fi.PPThe .PN logb(x) returns x's exponent n ,a signed integer converted to double\-precision floating\-point and sochosen that 1\0\(<=\0|\|x|/2**n\0<\02 unless x = 0 or.if n \|\|x| = infinity.if t \|\|x| = \(ifor x lies between 0 and the Underflow Threshold..PPScalb(x,n) = x\(**(2**n) computed, for integer n, without first computing2**N..SH DiagnosticsIEEE 754 defines drem(x,0) and.if n \drem(infinity,y).if t \drem(\(if,y)to be invalid operations that produce a \*(nn..PPIEEE 754 defines.if n \logb(\(+-infinity) = +infinity and logb(0) = \-infinity,.if t \logb(\(+-\(if) = +\(if and logb(0) = \-\(if, andrequires the latter to signal Division\-by\-Zero..SH RestrictionsIEEE 754 currently specifies thatlogb(denormalized no.) = logb(tiniest normalized no. > 0)but the consensus has changed to the specification in the new proposed IEEE standard p854, namely that logb(x) satisfy .RS1 \(<= scalb(|\|x|,\-logb(x)) < Radix\0\0\0... = 2 for IEEE 754.REfor every x except 0, .if n \infinity.if t \\(ifand \*(nn.Almost every program that assumes 754's specification will workcorrectly if logb follows 854's specification instead..PPIEEE 754 requires copysign(x,\*(nn) = \(+-x  but says nothingelse about the sign of a \*(nn..SH See Alsofloor(3M), fp_class(3), math(3M)