revised specification, updated readme, refactored main loop and imple…

…mentation

.gitignore

@@ -1,4 +1,7 @@
 .idea/
 CMakeLists.txt
 cmake-build-debug/
-.run
+.run
+*.exe
+*.o
+*~

README.md

@@ -1,4 +1,4 @@
-# Julius Caesar's Substitution Cipher!
+# Caleb's Caesar Shift/Substitution Cipher!
 Enter an integer (key) to left shift the normal alphabet by that number of positions.  
 Then, enter a message to encrypt using your new cipher alphabet.  
 🔥 FYI a key of 13 is effectively ROT-13.  

caesar-cipher.cpp

@@ -1,8 +1,5 @@
 #include "caesar-cipher.h"
 
-// https://www.tutorialspoint.com/cplusplus-program-to-implement-caesar-cypher
-// https://www.asciihex.com/
-
 using namespace std;
 
 void encryption(const string &plainAlpha) {
@@ -20,7 +17,7 @@ void encryption(const string &plainAlpha) {
         cin >> key;
     }
     cin.ignore(numeric_limits<streamsize>::max(), '\n');     // discard \n
-    cout << "Enter the message to encrypt: ";     // input message to encrypt
+    cout << "Enter the message to encrypt: ";                       // input message to encrypt
     getline(cin, message);
 
     // shift alphabet [key] letters to the left

caesar-cipher.h

@@ -9,21 +9,21 @@
 using namespace std;
 
 void encryption(const string&);
-// Function to display encrypt interface
-// Postcondition: const string is the alphabet displayed in plain then in ciphered
+// Function to display encrypt interface.
+// Postcondition: const string is the alphabet displayed in plain then in ciphered.
 
 void decryption(const string&);
-// Function to display decrypt interface
-// Postcondition: const string is the alphabet displayed in plain then in ciphered
+// Function to display decrypt interface.
+// Postcondition: const string is the alphabet displayed in plain then in ciphered.
 
 string cipherAlpha(int&, const string&);
 // Function to generate cipher alphabet.
-// Postcondition: const string is shifted left by const int positions
+// Postcondition: const string is alphabet shifted left by int positions.
 
 string cipherMessage(const string&, int&);
-// Function to encrypt the message
-// Postcondition: string message shifted left by int positions
+// Function to encrypt the message.
+// Postcondition: const string is message shifted left by int positions.
 
 string decrypt(const string&, int&);
-// Function to decrypt the message
-// Postcondition: string ciphertext shifted back to the right by int positions
+// Function to decrypt the message.
+// Postcondition: const string is ciphertext shifted back by int positions.

main.cpp

@@ -12,10 +12,10 @@ int main() {
     int option;
     string plainAlpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
-    while (cin) {
+    for(;;) {
         cout << "(1) Encrypt, (2) Decrypt, (0) Quit: ";
         cin >> option;
-        if (!cin) {
+        if (cin.fail()) {
             cin.clear();
             cin.ignore(numeric_limits<streamsize>::max(), '\n');
             cout << "Error! Invalid input." << endl;