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Diffstat (limited to 'Runnable.hs')
-rw-r--r-- | Runnable.hs | 59 |
1 files changed, 0 insertions, 59 deletions
diff --git a/Runnable.hs b/Runnable.hs deleted file mode 100644 index 56fedb3..0000000 --- a/Runnable.hs +++ /dev/null @@ -1,59 +0,0 @@ -{-# LANGUAGE ExistentialQuantification, MultiParamTypeClasses, FlexibleContexts, FlexibleInstances #-} ------------------------------------------------------------------------------ --- | --- Module : Xmobar.Runnable --- Copyright : (c) Andrea Rossato --- License : BSD-style (see LICENSE) --- --- Maintainer : Jose A. Ortega Ruiz <jao@gnu.org> --- Stability : unstable --- Portability : unportable --- --- The existential type to store the list of commands to be executed. --- I must thank Claus Reinke for the help in understanding the mysteries of --- reading existential types. The Read instance of Runnable must be credited to --- him. --- --- See here: --- http:\/\/www.haskell.org\/pipermail\/haskell-cafe\/2007-July\/028227.html --- ------------------------------------------------------------------------------ - -module Runnable where - -import Control.Monad -import Text.Read -import Config (runnableTypes) -import Commands - -data Runnable = forall r . (Exec r, Read r, Show r) => Run r - -instance Exec Runnable where - start (Run a) = start a - alias (Run a) = alias a - -instance Show Runnable where - show (Run x) = show x - -instance Read Runnable where - readPrec = readRunnable - -class ReadAsAnyOf ts ex where - -- | Reads an existential type as any of hidden types ts - readAsAnyOf :: ts -> ReadPrec ex - -instance ReadAsAnyOf () ex where - readAsAnyOf ~() = mzero - -instance (Show t, Read t, Exec t, ReadAsAnyOf ts Runnable) => ReadAsAnyOf (t,ts) Runnable where - readAsAnyOf ~(t,ts) = r t `mplus` readAsAnyOf ts - where r ty = do { m <- readPrec; return (Run (m `asTypeOf` ty)) } - --- | The 'Prelude.Read' parser for the 'Runnable' existential type. It --- needs an 'Prelude.undefined' with a type signature containing the --- list of all possible types hidden within 'Runnable'. See 'Config.runnableTypes'. --- Each hidden type must have a 'Prelude.Read' instance. -readRunnable :: ReadPrec Runnable -readRunnable = prec 10 $ do - Ident "Run" <- lexP - parens $ readAsAnyOf runnableTypes |