Arguments and values to get.

["Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>]

    Why does Common-Lisp GET take a default-value argument instead of
    returning a second value indicating whether the property actually
    exists?

The default argument is useful in some cases, but admittedly is a bit
inelegant -- if you want to know for sure whether a value was found, you
have to be careful to choose some default argument that couldn't
possibly be stored in any property list.  The reasoning (If I recall it
correctly) was that this occasional creation of a unique default is less
hassle than having to write an ugly multiple-value-bind every time we
want to return a default value in the property-not-found case.  I'm not
sure I believe that any more.

-- Scott