Because if/when we have real gensyms, where if we have
arc> (= gs (uniq))
gs2003
then (is gs 'gs2003) returns nil, instead of t (which it currently does), we won't be able to define uniq in Arc. It's another datatype (the "uninterned symbol"), and thus it needs an axiom. The axiom could be something besides uniq (string->uninterned-symbol, for instance, or usym) if (isnt (usym "foo") (usym "foo")).
Aha. So uniq in its current form is really 'kinda-uniq. How important is it that gensyms aren't equal to each other? I mean, if "everyone knows" /gs[0-9]+/ is "reserved" for gensyms, then all we need do is not make symbols matching that pattern. Thus is the language minimaler.
I'm just being lazy. It can't be that difficult to implement ...
And does that really make the language more minimal? If we leave uniq as it is, we could move it to arc.arc, but we have the axiom that symbols of the form /gs\d+/ are forbidden; if we change uniq, uniq is an axiom, but we don't have to worry about formats.
Even if Arc were not based on mzscheme the change would be minimal: it takes exactly the same operations as creating a normal symbol, with the difference that it doesn't have to be interned.
"doesn't have to be", or must not be interned? I'm thinking the latter, if the point is to guarantee that no other symbol shall be equal to a gensym ...
