Cabal-1.18.1: A framework for packaging Haskell software

Portabilityportable
Maintainer[email protected]
Safe HaskellSafe-Inferred

Distribution.Package

Contents

Description

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".

Synopsis

Package ids

type PackageId = PackageIdentifier

Type alias so we can use the shorter name PackageId.

Installed package identifiers

newtype InstalledPackageId

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

Describes a dependency on a source package (API)

Package classes

class Package pkg where

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.

Methods

packageId :: pkg -> PackageIdentifier

packageVersion :: Package pkg => pkg -> Version

class Package pkg => PackageFixedDeps pkg where

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.

Methods

depends :: pkg -> [PackageIdentifier]