gfse: edit abstract syntax in text mode with instant syntax error reporting

This is an experimental feature. It requires server support for parsing and is
thus not available while offline, unlike most other editing functionality.

src/compiler/SimpleEditor/JSON.hs

@@ -0,0 +1,47 @@
+module SimpleEditor.JSON where
+
+import Text.JSON
+
+import SimpleEditor.Syntax
+
+
+instance JSON Grammar where
+  showJSON (Grammar name extends abstract concretes) =
+    makeObj [prop "basename" name,
+             prop "extends" extends,
+             prop "abstract" abstract,
+             prop "concretes" concretes]
+
+instance JSON Abstract where
+  showJSON (Abstract startcat cats funs) =
+    makeObj [prop "startcat" startcat,
+             prop "cats" cats,
+             prop "funs" funs]
+
+instance JSON Fun   where showJSON (Fun   name typ) = signature  name typ
+instance JSON Param where showJSON (Param name rhs) = definition name rhs
+instance JSON Oper  where showJSON (Oper  name rhs) = definition name rhs
+
+signature  name typ = makeObj [prop "name" name,prop "type" typ]
+definition name rhs = makeObj [prop "name" name,prop "rhs" rhs]
+
+instance JSON Concrete where
+  showJSON (Concrete langcode opens params lincats opers lins) =
+    makeObj [prop "langcode" langcode,
+             prop "opens" opens,
+             prop "params" params,
+             prop "lincats" lincats,
+             prop "opers" opers,
+             prop "lins" lins]
+
+instance JSON Lincat where
+  showJSON (Lincat cat lintype) =
+    makeObj [prop "cat" cat,prop "type" lintype]
+
+instance JSON Lin where
+  showJSON (Lin fun args lin) =
+    makeObj [prop "fun" fun,
+             prop "args" args,
+             prop "lin" lin]
+
+prop name v = (name,showJSON v)