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Prototype: double frexp(double x, int *expptr);
Returns: the mantissa, or 0 if x is 0.
See also: ldexp, modf
The frexp function breaks down the floating-point value (x) into a mantissa
(m) and an exponent (n) such that the absolute value of m is greater than or
equal to 0.5 and less than 1.0, and x = m*2^n. The integer exponent n is
stored at the location pointed to by expptr.
Return Value
The frexp function returns the mantissa. If x is 0, the function returns 0
for both the mantissa and exponent. There is no error return.