S02: reserved namespace ops

S02 states "(Directly subscripting the type with either square brackets
or curlies is reserved for various generic type-theoretic operations. In
most other matters type names and package names are interchangeable.)"

What are these type-theoretic operations? And what do directly
attached < > pointy brackets on a type mean? How are they related
to « »? Is there something like ::_ as 'topic' type?

Here are the details of all four bracketing ops:

Foo($bar) # function call? constructor?
Foo .($bar) # same

Foo::($bar) # symbolic symbol lookup with outward scanning
Foo .::($bar) # same

Foo::<$bar> # direct symbol lookup without outward scanning
Foo::{'$bar'} # same
Foo .::<$bar> # same

Foo{$bar} # type constraint check?

Foo<$bar> # valid?
Foo«$bar» # valid?

Foo[$bar] # parametric type instanciation?

Foo::[$bar] # valid?
Foo .::[$bar] # same?
--

Um, I always thought that "is reserved" in a spec means "we don't have
the foggiest idea what we'll do with this, but we have a suspicion
that if we let people use this particular thing right now, we'll
regret it someday."

So I'm just saying that the conservative thing for now is to require
people to say MUMBLE::<$foo> and (for now) forbid them from saying MUMBLE<$foo>.

: Here are the details of all four bracketing ops:

s:g/valid\?/currently reserved/, but yes, that's pretty close to the current
state of affairs. You could remove the ? from Foo[$bar], I think.

Larry

OK, but how official is theory.pod? I mean is it part of the spec?
It definitly doesn't fit the synopsis numbering. It's more like
the track the Hogwart's express uses ;)
--

It's not official at all. Anything in the notes directory should be
considered to be in the same superpositional state as Schroedinger's Cat.

Larry