Re: [ANN] Lua 5.3.0 (work2) now available
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- Subject: Re: [ANN] Lua 5.3.0 (work2) now available
- From: Tim Hill <drtimhill@...>
- Date: 2014年3月26日 19:20:50 -0700
On Mar 26, 2014, at 3:28 PM, Roberto Ierusalimschy <roberto@inf.puc-rio.br> wrote:
>> I’m a bit ashamed to say that i do lol. Signum for example:
>>
>> static inline int sgn2(int x) { return (x != 0) * (1 | (x >> ((sizeof(x) * 8) - 1))); }
>
> "Hacker's Delight" suggests this:
>
> -(x >> K) | (-x >> K), where K = sizeof(x) * 8 - 1.
>
> No conditionals, no multiplications, two logical shifts and three one-clock
> instructions (2 subs and 1 or).
>
> -- Roberto
>
Nice. Wonder why I’ve not stumbled across that one before?
—Tim
- References:
- Re: [ANN] Lua 5.3.0 (work2) now available, Roberto Ierusalimschy
- Re: [ANN] Lua 5.3.0 (work2) now available, Coda Highland
- Re: [ANN] Lua 5.3.0 (work2) now available, Dirk Laurie
- Re: [ANN] Lua 5.3.0 (work2) now available, Coda Highland
- Re: [ANN] Lua 5.3.0 (work2) now available, Roberto Ierusalimschy
- Re: [ANN] Lua 5.3.0 (work2) now available, Tim Hill
- Re: [ANN] Lua 5.3.0 (work2) now available, Enrico Colombini
- Re: [ANN] Lua 5.3.0 (work2) now available, Tim Hill
- Re: [ANN] Lua 5.3.0 (work2) now available, Roberto Ierusalimschy
- Re: [ANN] Lua 5.3.0 (work2) now available, Tim Hill
- Re: [ANN] Lua 5.3.0 (work2) now available, Roberto Ierusalimschy