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For the code to function as before, a decryption function is added to the code. When the code is executed, this function reads the payload and decrypts it before executing it in turn. Encryption alone is not polymorphism. To gain polymorphic behavior, the encryptor/decryptor pair is mutated with each copy of the code.
Polymorphism is the phenomenon wherein somewhat interchangeable objects each expose an operation of the same name but possibly differing in behavior. As an example, a File object and a Database object both have a StoreRecord method that can be used to write a personnel record to storage. Their implementations differ.
As an example, an abstract base class MathSymbol may provide a pure virtual function doOperation(), and derived classes Plus and Minus implement doOperation() to provide concrete implementations. Implementing doOperation() would not make sense in the MathSymbol class, as MathSymbol is an abstract concept whose behaviour is defined solely for ...
As another, more significant, example of compile-time loop unrolling, template metaprogramming can be used to create length-n vector classes (where n is known at compile time). The benefit over a more traditional length-n vector is that the loops can be unrolled, resulting in very optimized code. As an example, consider the addition operator.
Notable examples of systems employing polymorphic recursion include Dussart, Henglein and Mossin's binding-time analysis [2] and the Tofte–Talpin region-based memory management system. [3] As these systems assume the expressions have already been typed in an underlying type system (not necessary employing polymorphic recursion), inference can ...
In the above example, the function Base<Derived>::interface(), though declared before the existence of the struct Derived is known by the compiler (i.e., before Derived is declared), is not actually instantiated by the compiler until it is actually called by some later code which occurs after the declaration of Derived (not shown in the above ...
Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
Ad hoc polymorphism is a dispatch mechanism: control moving through one named function is dispatched to various other functions without having to specify the exact function being called. Overloading allows multiple functions taking different types to be defined with the same name; the compiler or interpreter automatically ensures that the right ...