Frederik Eaton
On Sun, Sep 04, 2005 at 08:01:48PM -0700, Isaac Jones wrote:
The reason to combine them is that the point of abstraction between the compilers / interpreters lives in areas like "preprocess this file", "build this file", "install this library", not in operations like you mentioned:
I mentioned the second two of those, but not the first one.
You mentioned taking a .hs file and producing a .o file; that's not actually the same thing. Hugs doesn't use .o files, but if you look at Distribution.Simple.Build, you'll see that "building" for hugs (that is, preparing for installation) is far from a no-op. You mentioned "taking a package and installing it into a package database" but of course, Hugs doesn't have a package database, as we've discussed, and actually "installing" (that is, making libraries and executables available to end users) for Hugs is also not just a matter of copying some files over. So in short, the reason we don't put the level of abstraction into the operations you mention is because they aren't shared between the compilers / interpreters, so there's nothing to abstract. It's probably the case, though, that actual compilers like ghc, jhc, and nhc have much more similar models, and there could be some useful abstractions there.
Preprocessing files, however, doesn't sound like an operation that needs to be done in a compiler/interpreter-specific way.
That's true, ther's almost no compiler-specific code in Distribution.PreProcess, except to pass some definitions to CPP. peace, isaac
There would be operations such as: compile a file into an object file (may be a no-op); link a bunch of object files into a package; install a package into the following package database; create an empty package database; merge two package databases; find dependencies of a module. And options like: use the following other packages, search for packages in the following package database.
Each of these operations would be a no-op for Hugs, and yet the abstraction layer that Cabal provides works quite well for Hugs. I think that if we had built a standard command-line interface between compilers, GHC and Hugs would have almost disjoint operations, and Cabal would still have to perform the same amount of work, since it couldn't actually use this interface to get its job done.
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