Mark Lentczner schrieb:
Over on my blog, I've put up a proposal for changing the default layout of installed package pieces:
http://mtnviewmark.wordpress.com/2010/12/02/haskell-package-layout/
Thoughts?
About 1. A package A with a specific version v must provide a specific API independent of the compiler. If a package B imports A-v it cannot additionally check what compiler was used to compile A (and B, too). Thus documentation should really only depend on the package version. If there is a feature, that is available only for a specific compiler, then this must be moved into a separate package C. Package C can then be compiled completely or not on a given compiler, but not in parts. I have an additional problem with the current layout: You may use the same compiler version on different operating systems and processors, say Solaris/SPARC and Solaris/Intel. It's currently not possible to use them in parallel, unless you use different Cabal directories. In Modula-3 they define Targets, where a target specifies Operating system, Processor, Linker object format and compiler backend (GCC based or othes). In short: The target contains every feature, that can make an installed library different for the same compiler version. I have still a problem with the current local Cabal directory structure. Here everything is build below dist/build. I use Cabal in development and have long dependency chains and different compilers installed. If a basic package changes I have to recompile all dependent packages, but ghc's 'make' feature of recompiling only dependent modules does not help, because I have to recompile all modules, because dist/build cannot hold the compiled files for two compiler versions.