On Sat, May 12, 2018 at 5:54 PM Cameron Simpson <cs@cskk.id.au> wrote:
On 06May2018 02:00, Nick Coghlan <ncoghlan@gmail.com> wrote:
>On 5 May 2018 at 13:36, Tim Peters <tim.peters@gmail.com> wrote:
>> If only one trailing "given" clause can be given per `if` test
>> expression, presumably I couldn't do that without trickery.
>
>I was actually thinking that if we did want to allow multiple assignments,
>and we limited targets to single names, we could just use a comma as a
>separator:
>
>    if diff and g > 1 given diff = x - x_base, g = gcd(diff, n):
>        return g
>
>Similar to import statements, optional parentheses could be included in the
>grammar, allowing the name bindings to be split across multiple lines:
>
>    if diff and g > 1 given (
>        diff = x - x_base,
>        g = gcd(diff, n),
>    ):
>        return g

I'm well behind, but... this! This turns "given" into a +0.8 for me.

That's really nice. It reads clearly too.

I was hitherto in the "expression as name" camp, which I gather is already
rejected.

I love given, but that's the one thing I don't like.  I prefer this:
    if (diff and g > 1 
            given diff = x - x_base
            given g = gcd(diff, n)):
        return g

—just like for and if subexpressions.   Doing this can also open up weirdness if someone tries to roll something like:

a = f(),  # Make a tuple of length 1

into a given statement.  Now, where do you up the parentheses?

given (
    a = (f(),),
    b = whatever?
)

Seems weird.


Cheers,
Cameron Simpson <cs@cskk.id.au>
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