Cabal-1.18.0: A framework for packaging Haskell software

Safe HaskellSafe-Inferred




Defines a package identifier along with a parser and pretty printer for it. PackageIdentifiers consist of a name and an exact version. It also defines a Dependency data type. A dependency is a package name and a version range, like "foo >= 1.2 && < 2".


Package ids

type PackageId = PackageIdentifierSource

Type alias so we can use the shorter name PackageId.

Installed package identifiers

newtype InstalledPackageId Source

An InstalledPackageId uniquely identifies an instance of an installed package. There can be at most one package with a given InstalledPackageId in a package database, or overlay of databases.

Package source dependencies

data Dependency Source

Describes a dependency on a source package (API)

Package classes

class Package pkg whereSource

Class of things that have a PackageIdentifier

Types in this class are all notions of a package. This allows us to have different types for the different phases that packages go though, from simple name/id, package description, configured or installed packages.

Not all kinds of packages can be uniquely identified by a PackageIdentifier. In particular, installed packages cannot, there may be many installed instances of the same source package.

class Package pkg => PackageFixedDeps pkg whereSource

Subclass of packages that have specific versioned dependencies.

So for example a not-yet-configured package has dependencies on version ranges, not specific versions. A configured or an already installed package depends on exact versions. Some operations or data structures (like dependency graphs) only make sense on this subclass of package types.


depends :: pkg -> [PackageIdentifier]Source