On Fri, Oct 14, 2016 at 06:23:32PM +1300, Greg Ewing wrote:
> To maintain the identity
>
> list(*x for x in y) == [*x for x in y]
>
> it would be necessary for the *x in (*x for x in y) to expand
> to "yield from x".
Oh man, you're not even trying to be persuasive any more. You're just
assuming the result that you want, then declaring that it is
"necessary". :-(
I have a counter proposal: suppose *x is expanded to the string literal
"Nope!". Then, given y = (1, 2, 3) (say):
list(*x for x in y)
gives ["Nope!", "Nope!", "Nope!"], and
[*x for x in y]
also gives ["Nope!", "Nope!", "Nope!"]. Thus the identity is kept, and
your claim of "necessity" is disproven.
We already know what *x should expand to: nearly everywhere else, *x is
conceptually replaced by a comma-separated sequence of the items of x.
That applies to function calls, sequence unpacking and list displays.
The only exceptions I can think of are *args parameters in function
parameter lists, and sequence packing on the left side of an assignment,
both of which work in similar fashions.
But not this proposal: it wouldn't work like either of the above, hence
it would be yet another unrelated use of the * operator for some
special meaning.
--
Steve
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