1 files changed, 23 insertions, 0 deletions
diff --git a/examples/systemS/Proof.gf b/examples/systemS/Proof.gf
new file mode 100644
index 000000000..06a6f1c68
--- /dev/null
+++ b/examples/systemS/Proof.gf
@@ -0,0 +1,23 @@
+abstract Proof = Formula ** {
+
+  cat
+    Text ;
+    Proof ;
+    [Formula] ;
+
+  fun
+    Start : [Formula] -> Formula -> Proof -> Text ;
+
+    Hypo : Proof ;
+    Implic : [Formula] -> Formula -> Proof -> Proof ;
+    RedAbs : Formula -> Proof -> Proof ;
+    ExFalso : Formula -> Proof ;
+    ConjSplit : Formula -> Formula -> Formula -> Proof -> Proof ;
+    ModPon : [Formula] -> Formula -> Proof -> Proof ;
+    Forget : [Formula] -> Formula -> Proof -> Proof ;
+
+    DeMorgan1, DeMorgan2 : Formula -> Formula -> Proof -> Proof ;
+    ImplicNeg : [Formula] -> Formula -> Proof -> Proof ;
+    NegRewrite : Formula -> [Formula] -> Proof -> Proof ;
+
+}