List Comprehensions Enhancement

[William Tanksley]

On Tue, 14 Sep 1999 13:34:37 +1200, Greg Ewing wrote:
>William Tanksley wrote:
>> On 13 Sep 1999 13:32:47 GMT, Hannah Schroeter wrote:> 

>My goal wasn't to make the syntax as compact (some might
>say cryptic) as possible, but to import the idea and
>make it blend in with the rest of the language.

I liked it.

>> >Also, I think there should be a clear separator 
[he suggested a comma]

>> I agree -- my initial reaction was to put 'and' as the seperator.

>There are problems with both of those. Using "," would
>mean the expression couldn't be a tuple constructor without
>using parentheses, which would be a potentially confusing
>difference from the for statement.

I hear you here -- but I tried to write a couple of comprehensions, and I
found that I was putting parenthesis in when needed.  It's kind of
automatic after you've been working with Python for any amount of time.

>And I'm not sure what
>the parser would make of "x and for" given that "x and y"
>is a legal expression.

It's parsable, but given that it would require modifications to the parser
I have to retract my suggestion.

>Semicolons could perhaps be used, although that seems
>somehow un-pythonic to me.

I don't like it either.  Commas have the advantage of looking like they're
talking about sequences, which in this case they indeed are.

>Another possibility is to turn the whole thing around
>and write
>  [for i in nums: for s in strs: (i, s)]
>but that loses the declarative flavour of having the
>element expression up front.

Agreed.  It also looks a little too much like a normal Python statement,
which it's not really.

>> On a scale of one to ten I'd give it a tim.

>Hey, wow! And I haven't even gotten onto case statements
>with pattern matching yet...

Hey, Greg!  Make us a 'while' statement which reads lines out of a file.
And why doesn't Python have a $_ variable?

:-)

>Greg

-- 
-William "Billy" Tanksley