Re: Another scheme/dsssl question

[Chris Maden <crism@xxxxxxx>]

[Norm Walsh]
> Is it possible to test for the existance of a definition?
> 
> Suppose I want to make it possible for a derived stylesheet to
> override a value.  I'd like to write something like this:
> 
> (define default-foo '("x" "y" "z"))
> ...
> (if (some-predicate? foo)
>     foo
>     default-foo)
> 
> Is that possible?

You can test for procedure-ness with (procedure?).  It's not clear
from 8.5.10.1 that this will *only* return #t for things actually
(define)d, since the Standard defines data types in terms of
predicates that return #t for them, but it's worth a shot.

-Chris
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