Re: Must "attempt to get length of a number value" be an error?
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- Subject: Re: Must "attempt to get length of a number value" be an error?
- From: Sean Conner <sean@...>
- Date: Thu, 9 May 2019 16:49:04 -0400
It was thus said that the Great Egor Skriptunoff once stated:
> On Thu, May 9, 2019 at 7:59 PM Egor Skriptunoff wrote:
>
> > On Thu, May 9, 2019 at 7:43 PM Dirk Laurie wrote:
> >
> >>
> >> It's a ten-line patch to lvm.c:
> >> 534a535,544
> >> > case LUA_TNUMINT: {
> >> > lua_Integer n=ivalue(rb);
> >> > setivalue(ra,n<0?-n:n);
> >> > return;
> >> > }
> >>
> >
> > Ten lines are not enough.
> > What result would you expect for INT_MIN ?
> >
>
> BTW, math.abs(1<<63) in both Lua 5.3 and 5.4 returns negative value.
> That's a bug.
That's also a bug in most CPUs (those that are 2's complement), although a
number will set the overflow flag [1] to signal the condision [2].
-spc
[1] 6809, 8080, Z80, 68k series, x86 series do; other CPUs might as
well.
[2] The VAX doesn't. Also, there's no integer instruction on the MIPS
that does negation. There are two obvious sequences that will do
negation, but only one will trap on overflow.
- References:
- Re: Must "attempt to get length of a number value" be an error?, Coda Highland
- Re: Must "attempt to get length of a number value" be an error?, Philippe Verdy
- Re: Must "attempt to get length of a number value" be an error?, Coda Highland
- Re: Must "attempt to get length of a number value" be an error?, Philippe Verdy
- Re: Must "attempt to get length of a number value" be an error?, Coda Highland
- Re: Must "attempt to get length of a number value" be an error?, Philippe Verdy
- Re: Must "attempt to get length of a number value" be an error?, Coda Highland
- Re: Must "attempt to get length of a number value" be an error?, Dirk Laurie
- Re: Must "attempt to get length of a number value" be an error?, Egor Skriptunoff
- Re: Must "attempt to get length of a number value" be an error?, Egor Skriptunoff