Libraries and hierarchies

[Ross Paterson]

On Wed, Aug 06, 2003 at 12:34:41PM +0100, Simon Peyton-Jones wrote:
> Maybe you are saying "what happens if you graft two modules from
> different packages so that both modules get the same name?". For
> example, suppose we have two packages
> 
> 	dataOps-1.0	has a module with (relative) name A.B
> 	foo-2.7	has a module with (relative) name X.A.B
> 
> Suppose you graft in dataOps-1.0 at site DataOps.X
> and foo-2.7 at site DataOps
> 
> Then "import DataOps.X.A.B" is ambiguous: it could mean either module.
> 
> That is plainly an error.  To be consistent with name clashes within
> module, the complaint should probably only come if you actually try to
> import it.
> 
>  Was that what you meant?

Yes.  I would have thought that library authors would want to avoid
this.  I guess you don't mind: the library user just grafts one of the
libraries in somewhere else.  So the mapping supplied with the package is
presumably just a default that can be overridden.  And to read someone
else's source code I also need their personalized mappings for the
various packages they're using.

So you have extended the syntax of the language: you need a syntax for
these mappings, and the static semantics operates on ordinary source
plus this mapping language.