1. else on for
- Posted by kbochert at copper.net
Aug 08, 2003
--Alt-Boundary-10696.1125213
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On 6 Aug 2003 at 20:36, David Cuny wrote:
>
> I've implemented REDO, BREAK and CONTINUE in my own BASIC interpreter.
> Additionally, there is a ELSE clause on all the control structures, so if
> they complete without hitting a BREAK clause, the THEN executes:
>
> for i = 1 to length( s )
> if s[i] = 999 then
> break
> end if
> else
> printf( "999 was not found" )
> end for
>
> It saves having to set up a flag marking that something was found, and is
> cheap to implement.
>
I very much like this, but shouldn't the sense be reversed?
for i = 1 to length( s )
if s[i] = 999 then
break
end if
else
printf( "999 WAS found!!" )
end for
treating the 'break' as a sort of small-scale exception?
A loop being expected to run to completion, and a break
being abnormal?
By analogy with 'if - else'; The 'else' only executes when the
'for' doesn't (completely) execute.
Is 'else' the best name??
Any opinions?
Karl Bochert
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<div align="left"><font face="Arial"><span style="font-size:10pt">On 6 Aug 2003
at 20:36, David Cuny wrote:</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> I've implemented REDO, BREAK and CONTINUE in my own
BASIC interpreter. </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> Additionally, there is a ELSE clause on all the
control structures, so if </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> they complete without hitting a BREAK clause, the
THEN executes:</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> for i = 1 to length( s
)</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> if s[i] = 999
then</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">>
break</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> end
if</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> else</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> printf( "999
was not found" )</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> end for</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> It saves having to set up a flag marking that
something was found, and is </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> cheap to implement.</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">I very much
like this, but shouldn't the sense be reversed?</span></font></div>
<div align="left"><br/></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt"> </span></font><font face="Arial"><span
style="font-size:10pt"> for i = 1
to length( s )</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> if s[i] = 999
then</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt">
break</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> end
if</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> else</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> printf( "999 WAS
found!!" )</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> end for</span></font></div>
<div align="left"><br/></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">treating the
'break' as a sort of small-scale exception?</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">A loop being
expected to run to completion, and a break</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">being
abnormal?</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">By analogy
with 'if - else'; The 'else' only executes when the</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">'for' doesn't
(completely) execute.</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Is 'else' the
best name??</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Any
opinions?</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">
</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Karl
Bochert</span></font></div>
--Alt-Boundary-10696.1125213--
2. Re: else on for
Karl Bochert wrote:
> I very much like [else], but shouldn't the sense be reversed?
>
> for i = 1 to length( s )
> if s[i] = 999 then
> break
> end if
> else
> printf( "999 WAS found!!" )
> end for
I see what you mean, but no. At least, not the way Python implements it, which
is where I stole it from. Think of it this way: knowing the value was found
it the easy part. That it wasn't found is more problematic.
-- David Cuny
3. Re: else on for
- Posted by kbochert at copper.net
Aug 08, 2003
--Alt-Boundary-24703.13536828
Content-description: Mail message body
On 7 Aug 2003 at 7:00, David Cuny wrote:
>
>
> Karl Bochert wrote:
>
> > I very much like [else], but shouldn't the sense be reversed?
> >
> > for i = 1 to length( s )
> > if s[i] = 999 then
> > break
> > end if
> > else
> > printf( "999 WAS found!!" )
> > end for
>
> I see what you mean, but no. At least, not the way Python implements it, which
>
> is where I stole it from. Think of it this way: knowing the value was found
> it the easy part. That it wasn't found is more problematic.
>
Interesting. It took a while, but I understand (and agree!).
It is distressing that it could so thoroughly mislead me at first glance.
It does seem that 'else' here has a very different behavior than the else
in if-else.
Maybe:
for i = 1 to length( s )
if s[i] = 999 then
break
end if
then
printf ("999 NOT found")
end for
would be more consistant with the other uses of else & then.
The not found clause is 'after' rather than 'otherwise'.
Karl Bochert
--Alt-Boundary-24703.13536828
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<div align="left"><font face="Arial"><span style="font-size:10pt">On 7 Aug 2003
at 7:00, David Cuny wrote:</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> ============ The Euphoria Mailing List ============
</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> Karl Bochert wrote:</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > I very much like [else], but shouldn't the
sense be reversed?</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> ></span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > for i = 1 to length( s
)</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > if
s[i] = 999 then</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">>
>
break</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > end
if</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > else</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> >
printf( "999 WAS found!!" )</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> > end
for</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> I see what you mean, but no. At least, not the way
Python implements it, which </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> is where I stole it from. Think of it this way:
knowing the value was found </span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> it the easy part. That it wasn't found is more
problematic.</span></font></div>
<div align="left"><font face="Arial" color="#7f0000"><span
style="font-size:10pt">> </span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Interesting.
It took a while, but I understand (and agree!).</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">It is
distressing that it could so thoroughly mislead me at first
glance.</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">It does seem
that 'else' here has a very different behavior than the else</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">in
if-else.</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span
style="font-size:10pt">Maybe:</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> for i = 1 to length( s
)</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> if s[i] = 999
then</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt">
break</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> end
if</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> then</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> printf
("999 NOT found")</span></font></div>
<div align="left"><font face="Arial"><span
style="font-size:10pt"> end for</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">would be more
consistant with the other uses of else & then.</span></font></div>
<div align="left"><font face="Arial"><span style="font-size:10pt">The not found
clause is 'after' rather than 'otherwise'.</span></font></div>
<div align="left"><br/>
</div>
<div align="left"><font face="Arial"><span style="font-size:10pt">Karl
Bochert</span></font></div>
<div align="left"><br/>
</div>
<div align="left"></div>
--Alt-Boundary-24703.13536828--
4. Re: else on for
Hi Karl, you wrote:
> On 7 Aug 2003 at 7:00, David Cuny wrote:
>
>> Karl Bochert wrote:
>>
>>> I very much like [else], but shouldn't the sense be reversed?
>>>
>>> for i = 1 to length( s )
>>> if s[i] = 999 then
>>> break
>>> end if
>>> else
>>> printf( "999 WAS found!!" )
>>> end for
>>
>> I see what you mean, but no. At least, not the way Python implements it,
>> which
>> is where I stole it from. Think of it this way: knowing the value was found
>> it the easy part. That it wasn't found is more problematic.
>>
> Interesting. It took a while, but I understand (and agree!).
> It is distressing that it could so thoroughly mislead me at first glance.
I also like this idea in general, but totally agree with your worries.
> It does seem that 'else' here has a very different behavior than the else
> in if-else.
>
> Maybe:
>
> for i = 1 to length( s )
> if s[i] = 999 then
> break
> end if
> then
> printf ("999 NOT found")
> end for
>
> would be more consistant with the other uses of else & then.
'for ... then' is as confusing for me as 'for ... else'.
> The not found clause is 'after' rather than 'otherwise'.
That's also the way I understood it (but I don't know, if it's right.)
BTW: Does 'break' have the same effect as 'exit'?
How about this:
for i = 1 to length( s )
if s[i] = 999 then
exit
end if
finally
printf ("999 NOT found")
end for
Best regards,
Juergen
--
The difference between men and boys
is the price of their toys.
5. Re: else on for
Juergen wrote:
> BTW: Does 'break' have the same effect as 'exit'?
Yes, except that EXIT will trigger the ELSE clause. I just report the
behavior, I don't make it up. 
-- David Cuny
6. Re: else on for
> Yes, except that EXIT will trigger the ELSE clause. I just report the
> behavior, I don't make it up.
D'oh! I meant, EXIT _won't_ trigger the ELSE clause. Maybe I do just make this
stuff up, after all.
-- David Cuny
7. Re: else on for
Hi David, you wrote:
>> Yes, except that EXIT will trigger the ELSE clause. I just report the
>> behavior, I don't make it up.
>
> D'oh! I meant, EXIT _won't_ trigger the ELSE clause. Maybe I do just
> make this stuff up, after all.
>
> -- David Cuny
Ah, I see. Thanks for the clarification.
Best regards,
Juergen
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