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approx. of rational number of the form
M*2^E
FloatApprox(X: INT|RAT|RINGELEM, PrecBits: INT): RAT |
This function computes an approximation of the form
M*2^E to a rational number
X
where the mantissa satisfies
2^(PrecBits-1) <= |M| < 2^PrecBits-1 where
PrecBits is the specified bit precision. It gives 0 when applied to 0.
The updated version of this function is not backward compatible with the
old one; you must replace the 2nd arg by the number of bits you want in
the mantissa (see
FloorLog2, FloorLog10, FloorLogBase
).
The old fn is obsolescent and is now called
FloatApprox10
.
/**/ FloatApprox(1/3, 10);
683/2048
/**/ FloatApprox(1/3, 20);
699051/2097152
/**/ FloatApprox(123456789,8);
123207680
|