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

[Emil Lenngren]

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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