"Jim - FooBar();" <jimpil1...@gmail.com> writes:
> funny you should mention that!!! that is exactly what I meant by 'my
> fault'...I've come to realise that dynamic scope is almost evil, thus
> I go to great lengths to avoid it completely...in the rare cases where
> I do use it I always make sure it is bound to a init/default value :)
I do exactly the opposite when I use dynamic vars, that is, I define no
default value. For example, there's a function foo that uses a dynamic
var, and that must be bound and well-defined. Therefore, I provide a
macro to initially set it up, so that you write
(with-bar (foo bla))
and with-bar takes care of the proper initialization of that dynamic var
(which is not even visible to the user). When foo explodes because of
the var being Unbound, then it's obvious that the function was called
outside a with-bar macro and thus is a user error. A default value
would shadow such an error.
A real-world example of this design are many database query libs, where
you frequently have code like
(with-db-connection (make-me-a-db-connection url)
(select :from "foo" :where ...))
Bye,
Tassilo
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