Yet Another Switch-Case Syntax Proposal

[Michael Torrie]

On 04/06/2014 12:07 PM, Chris Angelico wrote:
> This has a slight oddity of parsing (in that an expression can
> normally have a comparison in it); if you really want to use the
> result of a comparison inside a case block, you'd have to parenthesize
> it. But it's easy enough to explain to a human.

This syntax is almost identical to the if/elif/else syntax, though, no?

> 
> case day in briefing_days:
>     lunch_time = datetime.time(11, 30)
>     meeting_time = datetime.time(12, 30)
> case not in briefing_days + festive_days:
>     lunch_time = datetime.time(12)
>     meeting_time = datetime.time(14)
> case in festive_days:
>     go_to_work = False
>     day_type = "festive"
> else:
>     go_to_work = True
>     day_type = "ferial"
> 
> A case statement that opens with a comparison operator takes the value
> from the previous case (without re-evaluating it); a case statement
> that lacks a comparison altogether assumes == and does the above. In
> either case (pardon the pun), the check will be done only if the
> preceding case was false. An 'else' clause is effectively equivalent
> to a 'case' that's always true.
> 
> Adds only one keyword to the language ("switch" is gone), and adds an
> edge case to parsing that's unlikely to come up in non-contrived code.
> 
> ChrisA
>