Some syntactic sugar proposals

Steven D'Aprano steve at REMOVE-THIS-cybersource.com.au
Tue Nov 16 11:42:39 CET 2010


On Mon, 15 Nov 2010 22:40:00 -0700, Ian Kelly wrote:

> On 11/15/2010 10:26 PM, Steven D'Aprano wrote:
>> t = foo()+bar()+baz() if pred(it) else baz()-foo()-bar()
>>
>> What does "it" mean here?
> 
> "it" would mean the result of the expression foo()+bar()+baz().  What
> else could it mean?

It could mean the last expression, baz(). Or the entire compound 
expression, foo()+bar()+baz().


> There are valid objections to the proposal, but the
> intended semantics seem perfectly clear.

Fair point, my example was terrible and didn't show the point that was 
clear in my head. Mea culpa. How about this instead?

t = foo()+it if pred(it) else bar()

Should that be a SyntaxError, or is `it` a variable that holds its value 
from statement to statement?

t = it

t = (foo() if pred(it) else bar()) if cond(it) else baz()


For what it's worth, Apple's defunct Hypertalk language had a couple of 
syntax elements very much like that. Hypertalk had a special variable, 
"it", which you used like this:

get the number of cards
put it into field "Card number"

I trust I don't have to explain this? :)

Hypertalk also had a special function, "the result", which worked 
something like this:

ask "This is a dialog box. Please type your answer here:"
put the result into field "Your answer"

(or you could use "result()" instead). Both of these worked quite well 
with Hypertalk, particularly with it's focus on non-programmers, but they 
were designed into the language from the beginning. In Python they would 
be the proverbial round peg in a square hole.

BTW, I frequently use "it" for iterators, and making "it" a reserved word 
would break a lot of my code. This would make me quite peeved.



-- 
Steven



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