OpenEuphoria

Re: 2.6 feature request: foreach

• Posted by Robert Craig <rds at RapidEuphoria.com> Jul 14, 2005
• 472 views

D. Newhall wrote:
> I think that the next release should have something new and useful to the
> language.
> Sure, you could do "continue" or "next" or something but will everyone use
> them? When
> I was looking at all the code I've written I realized that maybe around half
> of all
> my "for" loops were being used to reference each element in a sequence one
> after another.
> Due to this I think that a "foreach" statement would be a VERY useful addition
> to the
> language that I'm sure everyone would use.
> 
> It's syntax could go like so:
> 
> Instead of
> 
> sequence line
> line = gets(0)
> for i=1 to length(line)
>     if line[i] = -- something
>         -- code goes here
>     end if
> end for
> 
> One would type
> 
> sequence line
> line = gets(0)
> foreach element in line do
>     if element = -- something
>         -- code goes here
>     end if
> end foreach
> 
> Here "element" would implicitly be declared as an object and act just like the
> current
> loop variable in "for". However, after every iteration of the loop "element"
> will be
> set to the next next element in "line". A consideration would be to optimize
> expressions
> of the type "foreach obj in reverse(seq)do"

Thanks for the suggestion.
I thought about something like this about 10 years ago.
At first it looked like a good idea, but after trying
various examples and thinking it through, I felt it
might cause confusion. Short simple examples like the one
above are ok, but what if you have a loop with 100 statements
in it? The aliasing of one name for another might be hard to remember.
In the middle of a long section of code you could easily
forget that element = 99 really means (something like) line[i] = 99
(I assume you could read or write these loop variables).
Or element[5] += 1, really means (more or less) line[i][5] += 1
And could you change line in the middle of the loop? Would the
value of line be locked in. What if you saw:
line[j] = element
Would you instantly understand what it meant?
These issues made me think the feature was not
such a good thing to add to a language that is supposed to
be simple.

Thanks,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com