added a command for tree operations and started a module for defining them

src/GF/Command/TreeOperations.hs

@@ -0,0 +1,58 @@
+module GF.Command.TreeOperations (
+  treeOp,
+  allTreeOps
+  --typeCheck,
+  --compute
+  ) where
+
+import GF.Compile.TypeCheck
+import GF.Compile.AbsCompute
+
+-- for conversions
+import PGF.Data
+--import GF.Compile.GrammarToGFCC (mkType,mkExp)
+import GF.Grammar.Grammar
+
+
+type TreeOp = [Tree] -> [Tree]
+
+treeOp :: String -> Maybe TreeOp
+treeOp f = fmap snd $ lookup f allTreeOps
+
+allTreeOps :: [(String,(String,TreeOp))]
+allTreeOps = [
+   ("compute",("compute by using semantic definitions (def)",
+      id)),
+   ("smallest",("sort trees from smallest to largest, in number of nodes",
+      id)),
+   ("typecheck",("type check and solve metavariables; reject if incorrect",
+      id))
+  ]
+
+typeCheck :: PGF -> Tree -> (Tree,(Bool,[String]))
+typeCheck pgf t = (t,(True,[]))
+
+compute :: PGF -> Tree -> Tree
+compute pgf t = t
+
+
+
+{-
+data Tree = 
+   Abs [CId] Tree                   -- ^ lambda abstraction. The list of variables is non-empty
+ | Var CId                          -- ^ variable
+ | Fun CId [Tree]                   -- ^ function application
+ | Lit Literal                      -- ^ literal
+ | Meta Int                         -- ^ meta variable
+
+data Literal = 
+   LStr String                      -- ^ string constant
+ | LInt Integer                     -- ^ integer constant
+ | LFlt Double                      -- ^ floating point constant
+
+mkType :: A.Type -> C.Type
+mkType t = case GM.typeForm t of
+  Ok (hyps,(_,cat),args) -> C.DTyp (mkContext hyps) (i2i cat) (map mkExp args)
+
+mkExp :: A.Term -> C.Expr
+-}