frexp, ldexp, modf \- split into mantissa and exponent
.B double frexp(value, eptr)
.B double ldexp(value, exp)
.B double modf(value, iptr)
returns the mantissa of a double
\fIx\fP\|\(**\|2\u\fIn\fP\d
\fIvalue\|\(**\|2\u\fIexp\fP\d.
returns the positive fractional part of
and stores the integer part indirectly