We have
my $var # lexical scope temp $var # lexically-scoped dynamic scope
C<temp> is lexically scoped in that its effect goes away at the closing curly of the lexical scope that contains it.
A concept that we seem to be missing is the possibility of dynamically scoped dynamic scopes. I hesitate to come up with a syntax; but I can think of a couple of examples where it might be used. Caveat: if you beleive that globals are fundamentally evil, and that everything should be objects, then this is unnecessary. but for other people ...
Example 1: Create a dynamic scope, and then spawn N threads. Each thread has its own lexical scope. After each thread has done some work, each reaches a barrier. Once all the threads have reached that barrier, we terminate the dynamic scope that we previously introduced: the threads then continue in their lexical scopes, but with the different dynamic scope
Example 2: a state machine: imagine binding a number of variables into a "scope space", in which we then instance multiple scopes. We can then create a state machine in which we change the currently visible values of the scoped variables by changing the "current scope" of the "scope space".
One could imagine implementing this by creating the scopes as instances of an object, and then binding the object's attributes onto the variables (i.e. "our $foo := $obj.bar"). The "scope space" object would then be the set of global vaiables to be bound; and the "scope" object would be the set of values to bind.
However, when we want to release the global vaiables from our scope, then we need a way to unbind the variables, and restore them to the bindings that existed before they were bound to our scope space. I'm not sure how to do that, because we don't have any builtin concept of dynamically scoped scopes.
Dave.
