design question

[Thomas Schilling]

On 18 jul 2007, at 08.43, Sascha Böhme wrote:

> Hello,
>
> in Distribution.PackageDescription, one library may be given, but in
> Distribution.InstalledPackageInfo, several libraryDirs, importDirs,
> includeDirs, haddockInterfaces, haddockHTMLs may exist. Why is  
> this? How
> could there be more than one of these paths if there is just one
> library? I'm sure I miss some critical design decision.

(Just a guess.)

InstalledPackageDescription is different in that its format is not  
controlled by Cabal, but rather by the particular compiler.  It  
happens to be the case, that the formats are very similar, but there  
are some differences among Hugs, nhc, GHC, etc..
This data structure just captures these.

PackageDescription, OTOH, reflects Cabal's current capabilities.

HTH,

/ Thomas