src/Pure/term_xml.scala

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/term_xml.scala	Tue Jul 12 18:00:05 2011 +0200
@@ -0,0 +1,57 @@
+/*  Title:      Pure/term_xml.scala
+    Author:     Makarius
+
+XML data representation of lambda terms.
+*/
+
+package isabelle
+
+
+object Term_XML
+{
+  import Term._
+
+  object Encode
+  {
+    import XML.Encode._
+
+    val sort: T[Sort] = list(string)
+
+    def typ: T[Typ] =
+      variant[Typ](List(
+        { case Type(a, b) => (List(a), list(typ)(b)) },
+        { case TFree(a, b) => (List(a), sort(b)) },
+        { case TVar((a, b), c) => (List(a, int_atom(b)), sort(c)) }))
+
+    def term: T[Term] =
+      variant[Term](List(
+        { case Const(a, b) => (List(a), typ(b)) },
+        { case Free(a, b) => (List(a), typ(b)) },
+        { case Var((a, b), c) => (List(a, int_atom(b)), typ(c)) },
+        { case Bound(a) => (List(int_atom(a)), Nil) },
+        { case Abs(a, b, c) => (List(a), pair(typ, term)(b, c)) },
+        { case App(a, b) => (Nil, pair(term, term)(a, b)) }))
+  }
+
+  object Decode
+  {
+    import XML.Decode._
+
+    val sort: T[Sort] = list(string)
+
+    def typ: T[Typ] =
+      variant[Typ](List(
+        { case (List(a), b) => Type(a, list(typ)(b)) },
+        { case (List(a), b) => TFree(a, sort(b)) },
+        { case (List(a, b), c) => TVar((a, int_atom(b)), sort(c)) }))
+
+    def term: T[Term] =
+      variant[Term](List(
+        { case (List(a), b) => Const(a, typ(b)) },
+        { case (List(a), b) => Free(a, typ(b)) },
+        { case (List(a, b), c) => Var((a, int_atom(b)), typ(c)) },
+        { case (List(a), Nil) => Bound(int_atom(a)) },
+        { case (List(a), b) => val (c, d) = pair(typ, term)(b); Abs(a, c, d) },
+        { case (Nil, a) => val (b, c) = pair(term, term)(a); App(b, c) }))
+  }
+}