Data commit

Task/Stack/E/stack-2.e

@@ -0,0 +1,30 @@
+def makeStack() {
+    var store := null
+    def stack {
+        to push(x) { store := [x, store] }
+        to pop() { def [x, next] := store; store := next; return x }
+        to last() { return store[0] }
+        to empty() { return (store == null) }
+    }
+    return stack
+}
+
+? def s := makeStack()
+# value: <stack>
+
+? s.push(1)
+? s.push(2)
+? s.last()
+# value: 2
+
+? s.pop()
+# value: 2
+
+? s.empty()
+# value: false
+
+? s.pop()
+# value: 1
+
+? s.empty()
+# value: true