multistate 0.1.2 → 0.1.3.1

raw patch · 2 files changed

+110/−23 lines, 2 filesdep ~basedep ~mtldep ~tfp

Dependency ranges changed: base, mtl, tfp, transformers

Files

• example/Example.hs +76/−9
• multistate.cabal +34/−14

@@ -10,6 +10,7 @@ import Control.Applicative ( (<$>), (<*>) )  import Control.Monad.Trans ( lift )+import Control.Monad.Writer  {- Small example showing@@ -25,25 +26,91 @@ --                , MonadMultiState Char m --                , m~MultiStateT x IO) --             => m ()-examplePrint = do+simpleExamplePrint = do   c  <- mGet   cs <- mGet   lift $ putStrLn (c:cs) -exampleAction = do-  examplePrint+simpleExampleAction = do+  simpleExamplePrint   mSet 'J'-  examplePrint+  simpleExamplePrint -main = evalMultiStateT-     $ withMultiState 'H'-     $ withMultiState "ello, World!"-     $ exampleAction+simpleExample = do+  evalMultiStateT+    $ withMultiState 'H'+    $ withMultiState "ello, World!"+    $ simpleExampleAction --- output of main:+-- output: --  "Hello, World! --   Jello, World! --  "++-- and a more complex example:++newtype Account = Account Float+newtype Interest = Interest Float++setAccount :: MonadMultiState Account m => Float -> m ()+setAccount x = mSet (Account x)+getAccount :: MonadMultiState Account m => m Float+getAccount = do+  (Account x) <- mGet+  return x+modAccount :: MonadMultiState Account m => (Float -> Float) -> m ()+modAccount f = do+  (Account x) <- mGet+  mSet (Account (f x))++-- wait for a specific time, changing the account according to interest+wait :: ( MonadMultiState Account m+        , MonadMultiState Interest m )+     => Float+     -> m ()+wait t = do+  (Interest i) <- mGet+  (Account x) <- mGet+  mSet (Account (x*(1+i)**t))++logAccount :: ( MonadWriter [String] m+              , MonadMultiState Account m)+           => m ()+logAccount = do+  (Account x) <- mGet+  tell $ ["account balance = " ++ show x]++accountCalculation :: Writer [String] ()+accountCalculation = evalMultiStateT $ do+  tell ["account calculation start"]+  -- we cannot use any of the account methods here, because state is empty+  -- logAccount+  --   -->+  --   No instance for (Control.Monad.MultiState.ContainsType Account Null)+  withMultiState (Account 0.0) $ do -- state contains an Account.+    logAccount+    modAccount (+10.0)+    logAccount+    -- trying to use "wait" here would give type error, like above.+    withMultiState (Interest 0.03) $ do -- state now also contains Interest.+      wait 10.0 -- we can use wait, because state contains all+                -- necessary stuff.+      logAccount+      modAccount (\x -> x - 10.0)+      wait 10.0+      logAccount+      mSet (Interest 0.00)+      wait 10.0+    -- we can return back to the environment without interest+    -- but the changes to the account are still present+    logAccount+  -- and we can return to an empty state+  tell ["account calculation end"]++main = do+  simpleExample+  mapM_ putStrLn $ execWriter accountCalculation+  --whatIsNotPossible :: MultiStateT (Cons [Char] Null) IO () --whatIsNotPossible = mGet >>= (lift . print) -- type ambiguous

@@ -1,5 +1,5 @@ Name:          multistate-Version:       0.1.2+Version:       0.1.3.1 Cabal-Version: >= 1.8 Build-Type:    Simple license:       BSD3@@ -11,7 +11,7 @@ Bug-reports:   https://github.com/lspitzner/multistate/issues Stability:     Experimental category:      Control-tested-with:   GHC == 7.8.2+tested-with:   GHC == 7.6.3, GHC == 7.8.3  Synopsis: like mtl's ReaderT/StateT, but more than one contained value/type. Description:@@ -44,8 +44,24 @@   >      $ withMultiState "ello, World!"   >      $ examplePrint   .-  ( you can find this example as an executable in the package. )+  the output is:   .+  > Hello, World!+  > Jello, World!+  .+  ( you can find both this and a more complex example+    in an executable in the package. )+  .+  == Error Messages+  .+  If you try to execute an action that requires a specific type in the state,+  but the current state does not contain that type, the error message is+  something like+  .+  > Control.Monad.MultiState.ContainsType Foo Null+  .+  where @Foo@ is the missing type.+  .   == Known Deficits   .   This package currently lacks a complete set of "lifting instances", i.e.@@ -77,10 +93,10 @@     Control.Monad.MultiReader   other-modules:   build-depends:-    base >=4 && <6,-    mtl >=2 && <3,-    tfp >=0.8,-    transformers == 0.3.*+    base         >= 4.6   && <4.8,+    mtl          >= 2.1   && <2.3,+    tfp          >= 0.8   && <0.9,+    transformers >= 0.3   && <0.5   extensions:     GADTs     TypeFamilies@@ -97,10 +113,12 @@   if flag(build-test) {     buildable: True     build-depends:+      -- no version constraints necessary, because they are already+      -- given by library       multistate,-      base >= 4 && < 6,-      transformers == 0.3.*,-      tfp >=0.8+      base,+      tfp,+      transformers   } else {     buildable: False   }@@ -113,11 +131,13 @@   if flag(build-example) {     buildable: True     build-depends:+      -- no version constraints necessary, because they are already+      -- given by library       multistate,-      base >= 4 && < 6,-      transformers == 0.3.*,-      tfp >=0.8,-      mtl >=2 && <3+      base,+      mtl,+      tfp,+      transformers   } else {     buildable: False   }