Re: [ANN] Lua 5.3.0 (beta) now available

[Andrew Starks <andrew.starks@...>]

On Thursday, October 23, 2014, William Ahern <william@25thandclement.com> wrote:
> On Thu, Oct 23, 2014 at 03:37:32PM -0700, Coda Highland wrote:
> > On Thu, Oct 23, 2014 at 3:17 PM, William Ahern
> > <william@25thandclement.com> wrote:
> > >> That is, 2^7 +1 is -128 for a "signed char" (or whatever) or it's 129 for
> > >> an unsigned char, even though the rvalue's bits are the same...?
> > >
> > > I think you may have meant -127. But the bits are not necessarily the same.
> > > That's only the case in two's complement representation. You have to be
> > > careful about differentiating value and representation.[1]
> >
> > No, he meant -128, the range of a signed byte in two's complement is
> > -128 to +127.
> >
>
> I think you're missing the +1. 2^7 is 1000000 which is -128 in two's
> complement. But 2^7+1 is 10000001 which is -127.
>
> Try running:
>
> #include <stdio.h>
>
> int main(void) {
>         int i = (1<<7) + 1;
>         printf("signed:%d unsigned:%d\n", (char)i, (unsigned char)i);
>         return 0;
> }
>
> I get
>
> $ foo
> signed:-127 unsigned:129

I think that I meant something less technical. I mean that: an rvalue + the lvalue, which has a container/pointer type, provides more information than just the rvalue (presuming you know its size) and it provides different information than the same rvalue + a different lvalue of a different container type.  

I was wondering that is what Microsoft meant. 

-Andrew