variable declaration

[Steve Holden]

Thomas Bartkus wrote:

> "Steve Holden" <steve at holdenweb.com> wrote in message
> news:41FFAE20.7030802 at holdenweb.com...
> 
>>Thomas Bartkus wrote:
>>
>>
>>>"Carl Banks" <invalidemail at aerojockey.com> wrote in message
>>>news:1107205410.367521.50490 at f14g2000cwb.googlegroups.com...
>>><snip>
>>>
>>>>How common is it for a local variable to be bound in
>>>>more than one place within a function?
>>>
>>>
>>>How common?  It shouldn't happen at all and that was the point.
>>
>>This seems a little excessive to me. Sample use case:
>>
>>for something in lst:
>>   if type(something) != type(()):
>>     something = tuple(something)
> 
> 
> Hhhmmh!
> I presume you are going through the list and want to gaurantee that every
> item you encounter is a tuple!  So if it ain't - you just re-declare
> "something" to be a tuple. What was formerly a single string, integer,
> whathaveyou is now a tuple *containing* a single string, integer,
> whathaveyou.
> 
> Do you do it that way because you can? Or  because you must?
>    And
> If the former - is it a good idea?
> OR did I just miss your codes intent completely?
> 
I suspect you missed the intent completely.

> My first inclination would be to create a new variable (type = tuple) and
> accept (or typecast) each "something" into it as required. The notion that

OK, but if you do that then surely the loop looks like

for something in lst:
     somethingElse = something
     if type(somethingElse) != type(()):
         somethingElse = ...

> you just morph "something" still seems rather abhorrent. It hadn't occurred
> to me that iterating through a list like that means the iterater "something"
> might need to constantly morph into a different type according to a lists
> possibly eclectic contents.
> 
Now I suspect I'm missing *your* point.

> It might explain why the interpreter is incapable of enforcing a type.  It
> would forbid iterating through lists containing a mix of different types.
> EXCEPT- I must note, that other languages manage to pull off exactly such a
> trick with a variant type. When you need to pull off a feat such as this,
> you declare a variant type where the rules are relaxed *for that situation
> only* and there is no need to toss the baby out with the bathwater.
> 
Well I have to say that the longer I program (and I've been at it nearly 
forty years now) the more I am convinced that type declarations don't 
actually help. I can see their value in terms of code optimization, but 
there is no way that I see them as an error-detection mechanism. "You 
have tried to assign a string to an integer variable" just isn't a 
mistake I make a lot.

regards
  Steve
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Steve Holden                           http://www.holdenweb.com/