add unStr,unInt and unFloat in the Haskell binding

src/runtime/haskell-bind/PGF2.hsc

@@ -30,7 +30,7 @@ module PGF2 (-- * PGF
              -- ** Functions
              Fun,functions, functionsByCat, functionType, hasLinearization,
              -- ** Expressions
-             Expr,showExpr,readExpr,mkApp,unApp,mkStr,mkInt,mkFloat,
+             Expr,showExpr,readExpr,mkApp,unApp,mkStr,unStr,mkInt,unInt,mkFloat,unFloat,
              -- ** Types
              Type(..), Hypo, BindType(..), showType,
 

src/runtime/haskell-bind/PGF2/Expr.hsc

@@ -73,6 +73,16 @@ mkStr str =
       exprFPl <- newForeignPtr gu_pool_finalizer exprPl
       return (Expr c_expr exprFPl)
 
+-- | Decomposes an expression into a string literal
+unStr :: Expr -> Maybe String
+unStr (Expr expr master) =
+  unsafePerformIO $ do
+    plit <- pgf_expr_unlit expr (#const PGF_LITERAL_STR)
+    if plit == nullPtr
+      then return Nothing
+      else do s <- peekUtf8CString (plit `plusPtr` (#offset PgfLiteralStr, val))
+              return (Just s)
+
 -- | Constructs an expression from an integer literal
 mkInt :: Int -> Expr
 mkInt val =
@@ -82,6 +92,16 @@ mkInt val =
       exprFPl <- newForeignPtr gu_pool_finalizer exprPl
       return (Expr c_expr exprFPl)
 
+-- | Decomposes an expression into an integer literal
+unInt :: Expr -> Maybe Int
+unInt (Expr expr master) =
+  unsafePerformIO $ do
+    plit <- pgf_expr_unlit expr (#const PGF_LITERAL_INT)
+    if plit == nullPtr
+      then return Nothing
+      else do n <- peek (plit `plusPtr` (#offset PgfLiteralInt, val))
+              return (Just (fromIntegral (n :: CInt)))
+
 -- | Constructs an expression from a real number
 mkFloat :: Double -> Expr
 mkFloat val =
@@ -91,6 +111,16 @@ mkFloat val =
       exprFPl <- newForeignPtr gu_pool_finalizer exprPl
       return (Expr c_expr exprFPl)
 
+-- | Decomposes an expression into a real number literal
+unFloat :: Expr -> Maybe Double
+unFloat (Expr expr master) =
+  unsafePerformIO $ do
+    plit <- pgf_expr_unlit expr (#const PGF_LITERAL_FLT)
+    if plit == nullPtr
+      then return Nothing
+      else do n <- peek (plit `plusPtr` (#offset PgfLiteralFlt, val))
+              return (Just (realToFrac (n :: CDouble)))
+
 -- | parses a 'String' as an expression
 readExpr :: String -> Maybe Expr
 readExpr str =

src/runtime/haskell-bind/PGF2/FFI.hs

@@ -266,6 +266,9 @@ foreign import ccall "pgf/pgf.h pgf_expr_int"
 foreign import ccall "pgf/pgf.h pgf_expr_float"
   pgf_expr_float :: CDouble -> Ptr GuPool -> IO PgfExpr
 
+foreign import ccall "pgf/pgf.h pgf_expr_unlit"
+  pgf_expr_unlit :: PgfExpr -> CInt -> IO (Ptr a)
+
 foreign import ccall "pgf/pgf.h pgf_expr_unapply"
   pgf_expr_unapply :: PgfExpr -> Ptr GuPool -> IO (Ptr PgfApplication)