Em sáb., 27 de jun. de 2020 às 11:12, Richard Damon <
rich...@damon-family.org> escreveu:
> 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.
> >
> > Exactly.
> >
> > > 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 '_'.
> >
> > Steve
>
> 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.
>
> i.e.
>
> foo = 1
>
> def bar(baz):
>
> match baz:
>
> case 1: print('baz was one')
>
> case foo: print('baz was ', foo)
>
> bar(2)
>
> print(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)
>
> --
> Richard Damon
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>
I think that global binding make no sense, it will break a lot of code
silently, think about this
def bar(baz):
match baz:
case bar: pass
IMHO, the most obvious solution is that the bind should be available only
inside case block and if you need to change a global or a nonlocal you do
this explicitly inside the case block, if this is the case you can pickup a
bind name that doesn't shadow the desired variable. This way the intention
to overwrite a global/nonlocal is clear in code
--
“If you're going to try, go all the way. Otherwise, don't even start. ..."
Charles Bukowski
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