FREXP(3C-SVR4)      RISC/os Reference Manual       FREXP(3C-SVR4)



NAME
     frexp, ldexp, logb, modf, modff, nextafter, scalb - manipu-
          late 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.

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

DIAGNOSTICS
     If ldexp would cause overflow, +HUGE (defined in math.h) is
     returned (according to the sign of value), and errno is set



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FREXP(3C-SVR4)      RISC/os Reference Manual       FREXP(3C-SVR4)



     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 posi-
     tive 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 infin-
     ity, 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.




































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