 | cabal-query-0.1: Helpers for quering .cabal files or hackageDB's 00-index.tar | Source code | Contents | Index |
| Distribution.Query |
This package uses Data.Generics.PlateData, so
- when Cabal package format changes, we don't have to rewrite anything
- all queries are statically typed
- as a disadvantage, we may suffer some performance loss when doing very complex queries, anyway most of processing goes while we read package descriptions, not querying them
Example of enduser querying code:
module Main where
import qualified Data.ByteString.Lazy as B
import System.Environment
import Distribution.Query
import Distribution.Compiler
import Distribution.License
import Distribution.ModuleName hiding (main)
import Distribution.Package
import Distribution.PackageDescription
import Distribution.Version
import Distribution.Text
import Language.Haskell.Extension
main = (head `fmap` getArgs) >>=
B.readFile >>=
mapM_ (putStrLn . show . (x -> (display $ package x, display $ license x))) .
queryIndex (Not (Id (== GPL)) :& Not (Id (== BSD3)))
You can query any field of PackageDescription no matter how deep it is. You don't need to provide any type signature for comparison functions, which are wrapped in Id, as long as you use data constructors for which type can be inferred.
See PackageDescription fields for details.
| queryFiles :: Query -> [ByteString] -> [PackageDescription] | ||||||
| queryIndex :: Query -> ByteString -> [PackageDescription] | ||||||
|
| queryFiles | Source |
| :: Query | |
| -> [ByteString] | All files must be read as lazy ByteStrings |
| -> [PackageDescription] | Returns a list of package descriptions which satisfy the query |
| Queries .cabal files. | |
| queryIndex | Source |
| :: Query | |
| -> ByteString | The index file must be read as lazy ByteString |
| -> [PackageDescription] | Returns a list of package descriptions which satisfy the query |
| Queries an index file, which is commonly located at ~/.cabal/packages/hackage.haskell.org/00-index.tar in POSIX systems. | |
| data Query where | Source |
Heterogenous query tree. Example of constructed query: Not (Id (== GPL)) :& Not (Id (== BSD3)) Id takes comparison function as its argument. Commonly this must be a partially applied (/=) or (==). Data instance is required for PackageDescription traversal. All appropriate instances are generated automagically, so you don't have to bother as long as Cabal doesn't change its package description format. | ||||||||
| Constructors | ||||||||
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