module namespaces

Johannes Waldmann
Wed, 28 Feb 2001 11:17:22 +0100 (MET)

I think the namespace proposal wants to be strictly upward compatible,
therefore it's perhaps not the right time to discuss this ...
but still I think the question "why should the source text of a module
contain its name?" wants an answer.

Even if we stick to module headers, I don't really like the idea of
`module Fully.Qualified.Name where ..'

The proposal mentions the analogy to Java.
My knowledge of that is minimal, but in Java,
they have `package Foo.Bar.Frobs' (full name required)
and `class Frobble' (only last name there).
So, a Haskell module corresponds to what?

I understand the argument "the compiler needs to generate unique names
in the object files" but this is a matter of implementation,
about which the programmer (at least theoretically) should not care.

I think the underlying design decision here is:
how far should the user of a set of modules expect 
that he can move their source/interface/object files around,
and still  compile them/link against them  correctly.
The present proposal seems to imply: not at all.
This is a conservative answer. It is easy to implement, 
and guarantees some consistency. Is it too restrictive? 

But assume this policy is adopted. Then I am not allowed 
to move (precompiled) modules around physically.
That's why I want some means of renaming them (during importing),
and as I wrote earlier, not only for single modules (`import Foo as Bar')
but also for complete hierarchies (`import Leipzig.Standard as Standard')

A potential problem is that the root of some hierarchy 
perhaps is just a directory (that contains subdirs and modules) 
but not itself a module. One would need to write a dummy module
that just (qualified-)imports and re-exports all submodules.
But this had to be extended whenever a submodule is added.
This doesn't feel right. (On the other hand, the libFoo.a file
had to be rebuilt anyway on such an occasion.)

This leads to another question - during the linking stage: 
when should the compilation manager look for a single object file, 
and when should it expect an archive?

Anyway I think even the most restricitve form of hierarchical module names
would be very helpful. I certainly would start using it.
-- Johannes Waldmann ---- --
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