reorganized examples directory

[coq-hetmet.git] / examples / CommandSyntaxExample.hs

diff --git a/examples/CommandSyntaxExample.hs b/examples/CommandSyntaxExample.hs
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+++ b/examples/CommandSyntaxExample.hs
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+{-# OPTIONS_GHC -XModalTypes -XMultiParamTypeClasses -ddump-types -XNoMonoPatBinds  #-}
+module CommandSyntaxExample
+where
+
+--
+-- Please ignore this; I never got around to implementing it.
+--
+
+{-
+The example may seem a little contrived, but its purpose is to
+illustrate the be- haviour when the argument of mapC refers both to
+its parameter and a free vari- able (n).
+
+\begin{verbatim}
+-- we can use mapA rather than mapC (from page 100)
+
+mapA f = proc xs -> case xs of
+[] -> returnA -< [] x:xs’ -> do y <- f -< x
+ys’ <- mapA f -< xs’ returnA -< y:ys
+
+example2 =
+   <[ \(n,xs) -> 
+       ~(mapA <[ \x-> (~(delay 0) n, x) ]> )
+        xs
+    ]>
+
+<[ example2 (n,xs) =
+   ~(mapA <[ \x-> (~(delay 0) n, x) ]> ) xs ]>
+\end{verbatim}
+
+
+-- from Hughes' "programming with Arrows"
+
+mapC :: ArrowChoice arr => arr (env,a) b -> arr (env,[a]) [b] mapC c = proc (env,xs) ->
+case xs of [] -> returnA -< [] x:xs’ -> do y <- c -< (env,x)
+ys <- mapC c -< (env,xs’) returnA -< y:ys
+
+example2 = proc (n,xs) -> (| mapC (\x-> do delay 0 -< n
+&&& do returnA -< x) |) xs
+-}