The Caesar cipher is a simple and widely known encryption technique. The action of a Caesar cipher is to replace each letter in the unencrypted message (called "plaintext" in cryptography) with a different one a fixed number of places down the alphabet. The resulting message is called "ciphertext". For example: Plaintext: Hello, world! Ciphertext: Ebiil, tloia! The cipher illustrated above uses a left shift of three (or a right shift of 23), so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. Write a C++ function to implement the Caesar cipher, using the prototype:

precond: numpos>=0 and rshift<=26 postcond: the return value is the encrypted version of orig using the caesar(rshift) cipher string encryptCaesar(string orig, int rshift);

Your function should preserve case, and any non-alphabetic characters should be left unchanged. For example, encryptCaesar("Hello, world!",23) = "Ebiil, tloia!". You may write additional helper functions if you wish (and it will help you in later tasks). For example, one useful function may be to shift a single character some number of positions. Remember: Separation of Concerns!