frexp(3C)                      DG/UX 5.4R3.00                      frexp(3C)


NAME
       frexp, ldexp, logb, modf, modff, nextafter, scalb - manipulate parts
       of floating-point numbers

SYNOPSIS
       #include <math.h>

       double frexp (double value, int *eptr);

       double ldexp (double value, int exp);

       double logb (double value);

       double nextafter (double value1, double value2);

       double scalb (double value, double exp);

       double modf (double value, double *iptr);

       float modff (float value, float *iptr);

DESCRIPTION
       Every non-zero number can be written uniquely as x* 2n, where the
       ``mantissa'' (fraction) x is in the range 0.5 < |x| < 1.0, and the
       ``exponent'' n is an integer.  frexp returns the mantissa of a double
       value, and stores the exponent indirectly in the location pointed to
       by eptr.  If value is zero, both results returned by frexp are zero.

       ldexp and scalb return the quantity value* 2exp.  The only difference
       between the two is that scalb of a signaling NaN will result in the
       invalid operation exception being raised.

       logb returns the unbiased exponent of its floating-point argument as
       a double-precision floating-point value.

       modf and modff (single-precision version) return the signed
       fractional part of value and store the integral part indirectly in
       the location pointed to by iptr.

       nextafter returns the next representable double-precision
       floating-point value following value1 in the direction of value2.
       Thus, if value2 is less than value1, nextafter returns the largest
       representable floating-point number less than value1.

   Considerations for Threads Programming












Licensed material--property of copyright holder(s)                         1

frexp(3C)                      DG/UX 5.4R3.00                      frexp(3C)


                     +----------+-----------------------------+
                     |          |                      async- |
                     |function  | reentrant   cancel   cancel |
                     |          |              point    safe  |
                     +----------+-----------------------------+
                     |frexp     |     Y          N        N   |
                     |ldexp     |     Y          N        N   |
                     |logb      |     Y          N        N   |
                     |modf      |     Y          N        N   |
                     |modff     |     Y          N        N   |
                     |nextafter |     Y          N        N   |
                     |scalb     |     Y          N        N   |
                     +----------+-----------------------------+
DIAGNOSTICS
       If ldexp would cause overflow, ±HUGE (defined in math.h) is returned
       (according to the sign of value), and errno is set to ERANGE.  If
       ldexp would cause underflow, zero is returned and errno is set to
       ERANGE.  If the input value to ldexp is NaN or infinity, that input
       is returned and errno is set to EDOM.  The same error conditions
       apply to scalb except that a signaling NaN as input will result in
       the raising of the invalid operation exception.

       logb of NaN returns that NaN, logb of infinity returns positive
       infinity, and logb of zero returns negative infinity and results in
       the raising of the divide by zero exception.  In each of these
       conditions errno is set to EDOM.

       If input value1 to nextafter is positive or negative infinity, that
       input is returned and errno is set to EDOM.  The overflow and inexact
       exceptions are signalled when input value1 is finite, but
       nextafter(value1, value2) is not.  The underflow and inexact
       exceptions are signalled when nextafter(value1, value2) lies strictly
       between ±2-1022.  In both cases errno is set to ERANGE.

       When the program is compiled with the cc options -Xc or -Xa, HUGEVAL
       is returned instead of HUGE.

SEE ALSO
       cc(1), reentrant(3), intro(3M).


















Licensed material--property of copyright holder(s)                         2