Re: FOR loop limit

["Roger Harman" <RHarman@xxxxxxxxxx>]

Just to throw in a twist....

Take a look at DSPDTAARA output.  Offset 0 = Position (or Index) 1.  It
combines the best of both worlds.  

 

> > > shc@xxxxxxxxxxxxxxxxx 02/02/2009 1:14:53 PM >>>

On 02/02/2009, at 11:41 PM, Vern Hamberg wrote:

> I'm trying to figure this out, too. This is how a FOR loop is supposed
> to operate - the test exceeds the limit.

That's correct.

> The original question was why we start with 1

No, the original was a comment on observed behaviour i.e., that the  
index variable must be capable of holding a value at least 1 greater  
than the loop limit. That lead on to a pointless discussion of "Why  
is it so?" which in turn lead to unfounded supposition that the  
starting value may have some bearing on the terminal value.

> - example given was a FOR
> loop - but I suspect the question was really about array bases -
> zero-based for C/C++, say.

No, more that loops are frequently used to iterate over arrays  
therefore the starting value must have some relationship to the index  
of an array element. Some languages let you choose the boundary  
range--negative array indices anyone? In non-C-derived languages  
arrays are generally 1-based, In C-derived languages arrays are  
generally 0-based. However, in all programming languages (at least  
that I can think of), on for-loop termination, the index of the loop  
is always 1 greater than the terminal value--regardless of the  
starting value.

> I and others have offered some speculation on
> that, and have moved tangentially into errors when the loop counter  
> may
> exceed the limits of the data type used for that variable. So I'm  
> flatly
> getting a little lost!! See my last post in response to this.

No, that's where we started so if we're back to range errors on the  
loop index then we've come full-circle. So what are we discussing again?


Regards,
Simon Coulter.
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