[Template-haskell] RE: Template Haskell...

[Sean Seefried]

Hi Simon,

I realise that the following request might not, for good reasons, get 
implemented in Template Haskell either, but I think the ability to 
reify entire modules or reify functions from any module (including 
standard libraries) would be very useful to any person interested in 
language extension.

However, I realise that there are philosophical and implementation 
oriented problems with the idea.  Firstly, being able to reify code 
from another module means that all .hi files would bloat to many times 
their size as they now have to contain reified versions of the 
declarations in the modules and all this just in case someone happens 
to want to reify the declaration somewhere else.

Also, I realise that this partially breaks the abstraction mechanism of 
modules. One reason that we have modules and interfaces is so that we 
don't have to (or even *can't*) look inside the implementation of a 
module.

So how do I justify this feature being added?

Well as for the implementation difficulty I can't say that I've thought 
of a solution to this problem, but I think there is a philosophical 
difference between the user who is snooping around in modules they 
shouldn't be and the hard-working, honest meta-programmer who is using 
a program (not doing it themselves!) to manipulate code in another 
module.  In many cases they will be performing the arduous task of 
language extensions which is not exactly a task for beginners. Should 
they not have extra rights?

I will write a more reasoned proposal soon.

Cheers,

Sean