E language with samples

samples/E/Guards.E

@@ -0,0 +1,69 @@
+# from
+# http://wiki.erights.org/wiki/Walnut/Advanced_Topics/Build_your_Own_Guards
+def makeVOCPair(brandName :String) :near {
+
+    var myTempContents := def none {}
+
+    def brand {
+        to __printOn(out :TextWriter) :void {
+            out.print(brandName)
+        }
+    }
+
+    def ProveAuth {
+        to __printOn(out :TextWriter) :void {
+            out.print(`<$brandName prover>`)
+        }
+        to getBrand() :near { return brand }
+        to coerce(specimen, optEjector) :near {
+            def sealedBox {
+                to getBrand() :near { return brand }
+                to offerContent() :void {
+                    myTempContents := specimen
+                }
+            }
+            return sealedBox
+        }
+    }
+    def CheckAuth {
+        to __printOn(out :TextWriter) :void {
+            out.print(`<$brandName checker template>`)
+        }
+        to getBrand() :near { return brand }
+        match [`get`, authList :any[]] {
+            def checker {
+                to __printOn(out :TextWriter) :void {
+                    out.print(`<$brandName checker>`)
+                }
+                to getBrand() :near { return brand }
+                to coerce(specimenBox, optEjector) :any {
+                    myTempContents := null
+                    if (specimenBox.__respondsTo("offerContent", 0)) {
+                      # XXX Using __respondsTo/2 here is a kludge
+                        specimenBox.offerContent()
+                    } else {
+                        myTempContents := specimenBox
+                    }
+                    for auth in authList {
+                        if (auth == myTempContents) {
+                            return auth
+                        }
+                    }
+                    myTempContents := none
+                    throw.eject(optEjector,
+                                `Unmatched $brandName authorization`)
+                }
+            }
+        }
+        match [`__respondsTo`, [`get`, _]] {
+            true
+        }
+        match [`__respondsTo`, [_, _]] {
+            false
+        }
+        match [`__getAllegedType`, []] {
+            null.__getAllegedType()
+        }
+    }
+    return [ProveAuth, CheckAuth]
+}