       template.render(Box(["set": NSSet()]))!
     
     In order to render a section if and only if a set is not empty, you can
-    query its isEmpty ou count property (since 0 is falsey):
+    query its count property (since 0 is falsey):
     
     ::
     
       // Renders "Set elements are 3,1,2," and "Set is empty"
-      var template = Template(string: "{{#set.isEmpty}}Set is empty{{^}}Set elements are: {{#set}}{{.}},{{/set}}{{/}}")!
+      var template = Template(string: "{{#set.count}}Set elements are: {{#set}}{{.}},{{/set}}{{^}}Set is empty{{/}}")!
       template.render(Box(["set": NSSet(objects: 1,2,3)]))!
       template.render(Box(["set": NSSet()]))!
+    
+    Sets can not be queried for the key `isEmpty` on purpose. `set.isEmpty`
+    would evaluate to false in case of a missing set, and this would be soooo
+    misleading. So we recommend testing for `set.count` as above (which is
+    falsey for both empty and missing sets).
     */
     public override var mustacheBox: ObjCMustacheBox {
         return ObjCMustacheBox(MustacheBox(

                    // Support for both Objective-C and Swift arrays.
                    return Box(count)
                    
                case "isEmpty":
                    // Support for Swift arrays.
                    return Box(count == 0)
                    
                case "firstObject", "first":
                    // Support for both Objective-C and Swift arrays.
                    if count > 0 {

    
    Sets can be queried for the following key:
    
    - count: number of elements in the set
    - anyObject: any object of the set
    
    ::
    
      // Renders "3" and "0"
      template = Template(string: "{{set.count}}")!
      template.render(Box(["set": NSSet(objects: 1,2,3)]))!
