implementing type-level strings...

[hs-rrdtool.git] / Data / HList / String.hs

diff --git a/Data/HList/String.hs b/Data/HList/String.hs
index a51457ed3a336f055df4ae3866353011cdcdba62..bcec59c6d750ab623878087757d95302453fa7e3 100644 (file)
--- a/Data/HList/String.hs
+++ b/Data/HList/String.hs
@@ -1,6 +1,33 @@
 module Data.HList.String
-    (
+    ( HString
+    , hString
     )
     where
 
---import Data.HList.Prelude
+import Data.HList.Number
+import Data.HList.Prelude
+import Language.Haskell.TH
+import Language.Haskell.TH.Quote
+
+
+class HString s
+
+instance HString HNil
+
+instance HNat c => HString (HCons c s)
+
+hString :: QuasiQuoter
+hString = QuasiQuoter quoteStrExp quoteStrPat
+
+quoteStrExp :: String -> ExpQ
+quoteStrExp []     = varE (mkName "hNil")
+quoteStrExp (c:cs) = appsE [ varE (mkName "hCons")
+                           , hNatLiteralE (fromEnum c)
+                           , quoteStrExp cs
+                           ]
+
+quoteStrPat :: String -> PatQ
+quoteStrPat []     = varP (mkName "HNil")
+quoteStrPat (c:cs) = conP (mkName "HCons") [ hNatLiteralP (fromEnum c)
+                                           , quoteStrPat cs
+                                           ]