Question for Parisse about CAS floating point

[jgoizueta]

I was curious about the reason for the 48-bit precision of the CAS floating point values, so I took a peek at the source code of GIAC.

I see the gen class, which (when DOUBLEVAL is defined), uses its space for a double overlapped with the 8-bit type field, and that the type is rewritten when the gen used as a double, and zeroed when returning its double value (so effectively truncating the mantissa).

But that would remove 8 bits from the 53-bit double mantissa, making it 45, not 48 bits, which is what I get playing with Joe Horn’s hex (and the exponent range of double seems to be preserved too).

So, what am I missing?

And, on a different note, is there any chance of having DOUBLEVAL (or BCD) in the Prime?