[Python-ideas] Variations on a loop

[Chris Rebert]

On Wed, Aug 27, 2008 at 10:07 PM, Bruce Leban <bruce at leapyear.org> wrote:
> There are several different blocks of code you could tack onto a loop (I've
> deliberately chosen somewhat unusual words to express these here):
>
>     for x in items:
>         # body
>     interstitially:
>         # things to do between loop iteration
>         # (executed after each iteration in the loop when there is a next
> value)
>     subsequently:
>         # things to do after the last element of the loop is processed
>         # (when the loop is not exited by break)
>     contrariwise:
>         # things to do if the list was empty
>
> For example:
>
>     result = ""
>     for x in items:
>         result += str(x)
>     interstitially:
>         result += ", "
>     contrariwise:
>         result = "no data"
>
> When I first learned that Python had an 'else' clause on loops, I assumed it
> meant 'contrariwise'. I was surprised that it actually meant 'subsequently'.
>
> To be more clear, contrariwise is essentially equivalent to:
>
>     empty = True
>     for x in items:
>         empty = False
>         # body
>     if empty:
>         # do contrariwise code
>
> and interstitially is essentially equivalent to:
>
>     first = True
>     for x2 in items:
>         if not first:
>             # do interstitial code
>             first = False
>         x = x2
>         # body

Just for comparison, (assuming my Perl6 book is still accurate),
"interstitially" is equivalent to "NEXT" blocks in Perl6 and
"continue" blocks in Perl5.
I don't think that's necessarily a good thing, but anyway...

- Chris

========
Follow the path of the Iguana...
Rebertia: http://rebertia.com
Blog: http://blog.rebertia.com

>
> I think these are common/useful paradigms. I'm curious what others think.
>
> --- Bruce
>
>
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