update to use Control.GArrow instead of GHC.HetMet.GArrow

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

diff --git a/examples/GArrowPretty.hs b/examples/GArrowPretty.hs
new file mode 100644 (file)
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--- /dev/null
+++ b/examples/GArrowPretty.hs
@@ -0,0 +1,41 @@
+{-# LANGUAGE FunctionalDependencies, NoMonomorphismRestriction, MultiParamTypeClasses #-}
+module GArrowPretty(SourceCode(..),pprGArrow) where
+import Prelude hiding (id,(.))
+import Control.GArrow
+import Control.Category
+import Text.PrettyPrint.HughesPJ
+
+-- The Bool flag is to minimize the number of parentheses generated:
+-- it is true iff the principal connective is of lower precedence than
+-- juxtaposition
+data SourceCode a b = SC Bool Doc
+
+instance Category SourceCode where
+  id                  = SC False $ text "id"
+  (SC _ g) . (SC _ f) = SC True  $ f <+> (text ">>>") $$ g
+
+instance GArrow SourceCode (,) () where
+  ga_first     (SC x f) = SC True  $ text "ga_first"
+                                     <+> if x then parens f else f
+  ga_second    (SC x f) = SC True  $ text "ga_second"
+                                     <+> if x then parens f else f
+  ga_cancell            = SC False $ text "ga_cancell"
+  ga_cancelr            = SC False $ text "ga_cancelr"
+  ga_uncancell          = SC False $ text "ga_uncancell"
+  ga_uncancelr          = SC False $ text "ga_uncancelr"
+  ga_assoc              = SC False $ text "ga_assoc"
+  ga_unassoc            = SC False $ text "ga_unassoc"
+
+instance GArrowSwap SourceCode (,) () where
+  ga_swap             = SC False $ text "ga_swap"
+instance GArrowDrop SourceCode (,) () where
+  ga_drop             = SC False $ text "ga_drop"
+instance GArrowCopy SourceCode (,) () where
+  ga_copy             = SC False $ text "ga_copy"
+instance GArrowLoop SourceCode (,) () where
+  ga_loopl   (SC x f) = SC True  $ text "ga_loopl" <+> if x then parens f else f
+  ga_loopr   (SC x f) = SC True  $ text "ga_loopr" <+> if x then parens f else f
+
+pprGArrow :: SourceCode x y -> Doc
+pprGArrow (SC _ doc) = doc
+