Re: luasnmp and Counter64
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- Subject: Re: luasnmp and Counter64
- From: Drake Wilson <drake@...>
- Date: 2010年2月16日 22:49:49 -0600
PMFJI, but this is slightly too weird for me to not comment upon...
Quoth hleuwer <herbert.leuwer@t-online.de>, on 2010年02月17日 00:36:16 +0100:
> - hi = (u_long) floor(val / (double)(2 ^ ul_bits));
> - lo = (u_long) (val - hi * (double)(2 ^ ul_bits));
... does that really mean someone mistook ^ for exponentiation in C?
> + hi = floor(val / pow(2.0, ul_bits));
> + lo = val - hi * pow(2, ul_bits);
I wouldn't. ldexp exists from C89 and can do this by changing the
exponent part of the double (assuming binary floating point) rather
than doing a full numeric exponentiation:
val / pow(2.0, ul_bits) ==> ldexp(val, -ul_bits)
hi * pow(2.0, ul_bist) ==> ldexp(val, ul_bits)
where the second arguments are ints.
---> Drake Wilson