#include <math.h>
double logb(x) double x;
double scalb(x,y) double x; double y;
double significant(x) double x;
These functions allow users to verify compliance to ANSI/IEEE Std 754-1985 by running certain test vectors distributed by the University of California. Their use is not otherwise recommended; instead use scalbn(x,n) and ilogb(x) described in ieee_functions.3m See the [a manual with the abbreviation FPOINT] for details.
logb(x) returns the unbiased exponent of x in floating-point format, for exercising the logb(L) test vector. logb(±\(if) = +\(if; logb(0) = -\(if with a division by zero exception. logb(x) differs from ilogb(x) in returning a result in floating-point rather than integer format, in sometimes signaling IEEE exceptions, and in not normalizing subnormal x.
scalb(x,(double)n) returns x * 2**n computed by exponent manipulation rather than by actually performing an exponentiation or a multiplication, for exercising the scalb(S) test vector. Thus
significant(x) computes just
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