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mutable default parameter problem [Prothon]

Andrea Griffini agriff at tin.it
Wed Jun 16 17:48:21 EDT 2004 
On Wed, 16 Jun 2004 12:40:10 -0700, "Mark Hahn" <mark at prothon.org>
wrote:

>In Prothon:
>
>    def foo(x):
>            print foo.list.append!(x)
>    foo.list = []
>
>(Sorry. I couldn't resist bragging.)

The very first thing I tried was assigning foo.list
outside of the function (and, by the way, that works in
python too); this however doesn't mimic C++ static,
as initialization of the static local variable is done
in C++ when (and only IF) the function is entered.
The value used for initialization can for example
depend on local parameters or global state at *that time*.

Using "hasattr" seemed ugly to me at first, but after
all you need an additional flag anyway, so why not
checking the presence of a certain key in foo.__dict__ ?
That way both initialization and setting the flag are
done at the same time using just one clean statement.

The only (very small) syntax price is the if (that in
C++ is implicit in the overused keyword "static").

Andrea
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