cabal-install-solver/src/Distribution/Solver/Modular/Var.hs

   1 {-# LANGUAGE DeriveFunctor #-}
   2 module Distribution.Solver.Modular.Var (
   3     Var(..)
   4   , showVar
   5   , varPN
   6   ) where
   7
   8 import Prelude hiding (pi)
   9
  10 import Distribution.Solver.Modular.Flag
  11 import Distribution.Solver.Types.PackagePath
  12
  13 {-------------------------------------------------------------------------------
  14   Variables
  15 -------------------------------------------------------------------------------}
  16
  17 -- | The type of variables that play a role in the solver.
  18 -- Note that the tree currently does not use this type directly,
  19 -- and rather has separate tree nodes for the different types of
  20 -- variables. This fits better with the fact that in most cases,
  21 -- these have to be treated differently.
  22 data Var qpn = P qpn | F (FN qpn) | S (SN qpn)
  23   deriving (Eq, Ord, Show, Functor)
  24
  25 showVar :: Var QPN -> String
  26 showVar (P qpn) = showQPN qpn
  27 showVar (F qfn) = showQFN qfn
  28 showVar (S qsn) = showQSN qsn
  29
  30 -- | Extract the package name from a Var
  31 varPN :: Var qpn -> qpn
  32 varPN (P qpn)        = qpn
  33 varPN (F (FN qpn _)) = qpn
  34 varPN (S (SN qpn _)) = qpn