Consider lambdas literals + create literal axioms when an argument is a function

1 files changed, 30 insertions, 0 deletions

diff --git a/Test/hofs/Fold.dfy b/Test/hofs/Fold.dfy
new file mode 100644
index 00000000..df7d0126
--- /dev/null
+++ b/Test/hofs/Fold.dfy
@@ -0,0 +1,30 @@
+// RUN: %dafny /compile:3 "%s" > "%t"
+// RUN: %diff "%s.expect" "%t"
+
+datatype List = Nil | Cons(A,List<A>);
+
+datatype Expr = Add(List<Expr>) | Mul(List<Expr>) | Lit(int);
+
+function method Eval(e : Expr): int
+{
+  match e
+    case Add(es) => Fold(es,0,(e,v) requires e < es => Eval(e) + v)
+    case Mul(es) => Fold(es,1,(e,v) requires e < es => Eval(e) * v)
+    case Lit(i)  => i
+}
+
+function method Fold(xs : List<A>, unit : B, f : (A,B) -> B): B
+  reads f.reads;
+  requires forall x : A, y: B :: x < xs ==> f.requires(x,y);
+{
+  match xs
+    case Nil => unit
+    case Cons(x,xs) => f(x,Fold(xs,unit,f))
+}
+
+method Main() {
+  var two := Lit(2);
+  var add := (x,y) => Add(Cons(x,Cons(y,Nil)));
+  assert Eval(add(two,two)) == 4;
+  print "3 = ", Eval(add(Lit(1),two)), "\n";
+}