On 6/27/20 5:36 AM, Stephen J. Turnbull wrote:
Richard Damon writes:
I thought _ was also commonly used as:
first, -, last = (1, 2, 3)
as a generic don't care about assignment.
It is. But there are other options (eg, 'ignored') if '_' is used for translation in the same scope.
I guess since the above will create a local, so not overwrite a 'global' function _ for translations, so the above usage works as long as that function (or whatever namespace you are in) doesn't use _ for translations.
As long as the bindings in match also make the symbol a local (which seems reasonable) then you would get a similar restriction.
It's quite different. First, it surely won't make other symbols match-local. Of course there will be times when you do all the work inside the match statement. But often you'll want to do bindings in a match statement, then use those outside. The second problem is that this use of '_' isn't optional. It's part of the syntax. That means that you can't use the traditional marking of a translateable string (and it's not just tradition; there is a lot of external software that expects it) in that scope.
So it's practically important, if not theoretically necessary, that 'case _' not bind '_'.
I wasn't imply local to the match statement, but if the match is used inside a function, where using the binding operatior = will create a local name, even if there is a corresponding global name that matches (unless you use the global statement), will a match statement that binds to a name that hasn't bee made a local name by having an explicit assignment to it, actually bind to a global that might be present, or will it create a local? My first feeling is that binding to the global would be surprising.
foo = 1
case 1: print('baz was one')
case foo: print('baz was ', foo)
will this script create a new foo name inside bar, so that when we return, the module global foo is still 1, or did be bind to the global and change it?
Rebinding a global without a global statement would be unexpected (normally we can mutate the global, but not rebind it)