 // Either a special form, evaluated at compile time, or a regular word, evaluated at runtime.
 struct Definition {
     enum Body {
-        // TODO: The initial idea was to associate a closure containing code to execute 
-        // when compiling the special form.  However, this triggers lots of weird behavior
-        // from the Swift compiler so use a string for the time being.
-        case SpecialForm(handler: String)
-        
+        case SpecialForm
         case Regular(phrase: CompiledPhrase)
-        
-        var isSpecialForm : Bool {
-            switch self {
-            case .SpecialForm(_):
-                return true
-            default:
-                return false
-            }
-        }
     }
     
     let name: String

    
    func isSpecialForm(name: String) -> Bool {
        if let def = self[name] {
            if def.body.isSpecialForm {
                return true
            }
        }
        return false

            phraseBeingCompiled.appendInstruction(.PushConstant(n))
        } else if let def = dictionary[token] {
            switch def.body {
            case .SpecialForm:
                let success = compileSpecialForm(token)
                if !success {
                    return false
                }
