reintroduce the compiler API

src/compiler/api/GF/Compile/PGFtoJava.hs

@@ -0,0 +1,43 @@
+module GF.Compile.PGFtoJava (grammar2java) where
+
+import PGF2
+import Data.Maybe(maybe)
+import Data.List(intercalate)
+import GF.Infra.Option
+
+-- | the main function
+grammar2java :: Options
+                -> String  -- ^ Module name.
+                -> PGF
+                -> String
+grammar2java opts name gr = unlines $  
+  javaPreamble name ++ methods ++ javaEnding
+  where
+    methods = [javaMethod gr fun | fun <- functions gr]
+
+javaPreamble name =
+ [
+  "import org.grammaticalframework.pgf.*;",
+  "",
+  "public class " ++ name ++ " {",
+  ""
+ ]
+ 
+javaMethod gr fun =
+  "  public static Expr "++fun++"("++arg_decls++") { return new Expr("++show fun++args++"); }"
+  where
+    arity = maybe 0 getArrity (functionType gr fun)
+    vars  = ['e':show i | i <- [1..arity]]
+    
+    arg_decls = intercalate "," ["Expr "++v | v <- vars]
+    args      = if null vars then ",new Expr[] {}" else ","++intercalate "," vars
+
+    getArrity ty = length hypos
+      where
+        (hypos,_,_) = unType ty
+
+javaEnding =
+ [
+  "",
+  "}"
+ ]