[Gambas-user] R: Unending cycle "For...Next" with variable As Byte

[Ru Vuott]

...may we adfirm: " A cycle, to end, must reach the upper limit to its maximum extreme. "  ?





--- Dom 30/9/12, Emil Lenngren <emil.lenngren at ...626...> ha scritto:

> Da: Emil Lenngren <emil.lenngren at ...626...>
> Oggetto: Re: [Gambas-user] R: Unending cycle "For...Next" with variable As Byte
> A: "mailing list for gambas users" <gambas-user at lists.sourceforge.net>
> Data: Domenica 30 settembre 2012, 23:27
> It is the same in almost all
> languages.
> 
> unsigned char i;
> for(i=0; i<255; i++){}
> and
> unsigned int i;
> for(i=0; i<4294967295U; i++){}
> in C will never terminate.
> 
> In Gambas,
> Dim i As Integer
> For i = 0 To 2147483647
> Next
> will not terminate either.
> 
> You might think that because you say the range 0 To X, you
> expect to get
> each of those values, but the truth is that the For i = 0 To
> X is actually
> interpreted as for(i=0; i<=X; i++) which obviously does
> not work when X is
> the max value of that integer type.
> 
> 2012/9/30 RICHARD WALKER <richard.j.walker at ...247...>
> 
> > Sinclair BASIC on the QL used to have a FOR loop
> epilogue which could
> > be used to handle this sort of thing. A simple FOR loop
> was
> >
> > FOR index = start TO stop
> >
> >
> > On 30/09/2012, Jussi Lahtinen <jussi.lahtinen at ...626...>
> wrote:
> > > I think all Basics work this way!
> > >
> > > Test with any basic:
> > >
> > > For ii = 1 to 10
> > > Next
> > >
> > > Print ii
> > >
> > > What you expect? I think all basic languages gives
> 11 as result.
> > >
> > > Jussi
> > >
> > >
> > >
> > >
> > >
> > > On Sun, Sep 30, 2012 at 10:14 PM, Kevin Fishburne
> <
> > > kevinfishburne at ...1887...>
> wrote:
> > >
> > >> This one bit me a while back and the answer
> was the same and I confirmed
> > >> it through testing. Maybe the documentation
> for For...Next should
> > >> mention it. I suspect many BASIC dialects
> don't work this way, which
> > >> could lead to confusion for new users of
> GAMBAS. I could be wrong, but I
> > >> think even GAMBAS used to not work this way,
> which makes the issue even
> > >> more confusing. Then again, the root of the
> issue doesn't really have
> > >> anything to do with For...Next but in how
> variables deal with
> > >> assignments that are out of range.
> > >>
> > >> On 09/30/2012 11:40 AM, Jussi Lahtinen wrote:
> > >> > It is not bug, Richard is right.
> > >> >
> > >> > Jussi
> > >> >
> > >> >
> > >> >
> > >> > On Sun, Sep 30, 2012 at 6:32 PM, Tobias
> Boege <taboege at ...626...>
> > >> > wrote:
> > >> >
> > >> >> On Sun, 30 Sep 2012, Ru Vuott wrote:
> > >> >>> ...I have:
> > >> >>>
> > >> >>> [Gambas 3]
> > >> >>> Version=3.3.0
> > >> >>>
> > >> >>>
> > >> >>>
> > >> >>>
> > >> >>>
> > >> >>> --- Dom 30/9/12, Ru Vuott <vuott at ...325...>
> ha scritto:
> > >> >>>
> > >> >>>> Da: Ru Vuott <vuott at ...325...>
> > >> >>>> Oggetto: [Gambas-user]
> Unending cycle "For...Next" with variable As
> > >> >> Byte
> > >> >>>> A: gambas-user at lists.sourceforge.net
> > >> >>>> Data: Domenica 30 settembre
> 2012, 16:57
> > >> >>>> Hello,
> > >> >>>>
> > >> >>>> maybe I'm in the clouds....
> but I don't understand why this
> > >> >>>> cycle:
> > >> >>>>
> > >> >>>> **********
> > >> >>>> Public Sub Button1_Click()
> > >> >>>>
> > >> >>>> ? Dim j As Byte
> > >> >>>>
> > >> >>>> ? For j = 0 To 255
> > >> >>>>
> > >> >>>> ???Print j
> > >> >>>>
> > >> >>>> ? Next
> > >> >>>>
> > >> >>>> End
> > >> >>>> **********
> > >> >>>>
> > >> >>>> runs "ad infinitum" !
> > >> >>>>
> > >> >>>> Regards
> > >> >>>> vuott
> > >> >>>>
> > >> >> Can confirm that with rev5189.
> Richard's guess sounds logical. "For
> > >> >> To"
> > >> is
> > >> >> inclusive: [0; 255] and that's
> everything you can represent with Byte
> > >> >> width.
> > >> >> You won't ever detect Byte > 255.
> > >> >>
> > >> >>
> > >>
> > >> --
> > >> Kevin Fishburne
> > >> Eight Virtues
> > >> www: http://sales.eightvirtues.com
> > >> e-mail: sales at ...1887...
> > >> phone: (770) 853-6271
> > >>
> > >>
> > >>
> > >>
> >
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