Programming Forums > Application Development > C++

Sane · Dec 7th, 2005, 5:30 PM

I need to learn C++ for school soon, so I thought I'd get started sooner with a quick script. This demonstrates the Vigenere Cypher, nothing too deep in the code. It's only heavily commented because I had to sell it.

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#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string.h>
using namespace std;

string Qualify(string text)                     // this will get rid of all non A-Z letters
{
    string result ("");                         // the result of the function
    int lp, let_val;                            // the loop indicator, and ascii value var
                    
    strupr((char *) text.c_str());              // convert all characters to upper case
     
    for(lp = 0; lp < text.length(); lp++)       // loop through every character in 'text'
    {   
        let_val = int(text[lp]);                // get the ascii value of the letter
        if (let_val > 64 && let_val < 91)       // if the letter is between 'A' and 'Z'
        {
            result += text[lp];                 // keep this letter               
        }
    }                                            
    return (result);                            // give back the result
}


string VigenereCypher(string text, string key)  // this encrypts a string into a Vigenere Cypher
{
    string result ("");                         // the result of our function
    text = Qualify(text);                       // remove the spaces and upper-case 'text'
    key = Qualify(key);                         // same to the 'key'
    
    int key_len(key.length()), lp, let_val, key_val; 
                                                // declared our variables
    for(lp = 0; lp < text.length(); lp++)       // loop through each character in 'text'
    {
        let_val = int(text[lp]);                // get the ascii value of the letter
        key_val = int(key[lp % key_len]);       // get the ascii value of our current key letter

/*  
basically, the Vigenere Cypher changes the value of the current letter by 
an amount equal to the current letter of the key, so to do this we must: 
  - add the two values together and subtract by 130 to get a value from 0-50,
  - confine the result to 0-25 by finding the remainder (%) of dividing by 26,
  - add the number to 65, because 65 = A, 66 = B, etc,
  - convert to ascii, then append to result */
        result += char((let_val + key_val - 130) % 26 + 65);
    } 
    return (result);                            // give back the result
}


int main ()
{
    string cypher, key, text;                   // declare variables

    cout << "Enter the text (no spaces): ";     // no spaces allowed in cin
    cin >> text;                                // get text from user

    cout << "Enter the key: ";
    cin >> key;                                 // get key from user
    
    cypher = VigenereCypher(text, key);         // using the text and key, get cypher
    
    ofstream ofile;
    ofile.open ("VigenereCyphers.txt", ofstream::out | ofstream::app);
    ofile << "Text:\n - " << text << "\nKey:\n - " << key << "\nCypher:\n - " << cypher << "\n\n";
    ofile.close();                              // appended all data to a text file
    
    cout << cypher << endl;                     // display the cypher
    cout << "\nAppended to: VigenereCyphers.txt" << endl;

    system("PAUSE");                            // wait for the user to press a key
    return 0;
}

#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string.h>
using namespace std;

string Qualify(string text)                     // this will get rid of all non A-Z letters
{
    string result ("");                         // the result of the function
    int lp, let_val;                            // the loop indicator, and ascii value var
                    
    strupr((char *) text.c_str());              // convert all characters to upper case
     
    for(lp = 0; lp < text.length(); lp++)       // loop through every character in 'text'
    {   
        let_val = int(text[lp]);                // get the ascii value of the letter
        if (let_val > 64 && let_val < 91)       // if the letter is between 'A' and 'Z'
        {
            result += text[lp];                 // keep this letter               
        }
    }                                            
    return (result);                            // give back the result
}


string VigenereCypher(string text, string key)  // this encrypts a string into a Vigenere Cypher
{
    string result ("");                         // the result of our function
    text = Qualify(text);                       // remove the spaces and upper-case 'text'
    key = Qualify(key);                         // same to the 'key'
    
    int key_len(key.length()), lp, let_val, key_val; 
                                                // declared our variables
    for(lp = 0; lp < text.length(); lp++)       // loop through each character in 'text'
    {
        let_val = int(text[lp]);                // get the ascii value of the letter
        key_val = int(key[lp % key_len]);       // get the ascii value of our current key letter

/*  
basically, the Vigenere Cypher changes the value of the current letter by 
an amount equal to the current letter of the key, so to do this we must: 
  - add the two values together and subtract by 130 to get a value from 0-50,
  - confine the result to 0-25 by finding the remainder (%) of dividing by 26,
  - add the number to 65, because 65 = A, 66 = B, etc,
  - convert to ascii, then append to result */
        result += char((let_val + key_val - 130) % 26 + 65);
    } 
    return (result);                            // give back the result
}


int main ()
{
    string cypher, key, text;                   // declare variables

    cout << "Enter the text (no spaces): ";     // no spaces allowed in cin
    cin >> text;                                // get text from user

    cout << "Enter the key: ";
    cin >> key;                                 // get key from user
    
    cypher = VigenereCypher(text, key);         // using the text and key, get cypher
    
    ofstream ofile;
    ofile.open ("VigenereCyphers.txt", ofstream::out | ofstream::app);
    ofile << "Text:\n - " << text << "\nKey:\n - " << key << "\nCypher:\n - " << cypher << "\n\n";
    ofile.close();                              // appended all data to a text file
    
    cout << cypher << endl;                     // display the cypher
    cout << "\nAppended to: VigenereCyphers.txt" << endl;

    system("PAUSE");                            // wait for the user to press a key
    return 0;
}

And I realise there's some "bad form", like system("PAUSE"). But I couldn't do cin.get(), because after the user hits enter from the last cin, it seems to carry through over to cin.get().

Oh well, wee.

Ooble · Dec 7th, 2005, 5:36 PM

Noice.

BTW, try:

(Toggle Plain Text)

cin.sync(); // clears the input buffer (apparently)
cin.get();

Jessehk · Dec 7th, 2005, 5:57 PM

And just for future reference, a C++ program is not a script

nnxion · Dec 7th, 2005, 6:56 PM

Not bad for a first try. You should use <cstdlib> and <string> instead of <stdlib.h> and <string.h>. Using namespace std is also (often) not good practice. Instead try: using std::cout; etc.
You also know that you are relying on the ascii character set here, and that other character sets might not have A at 65.

Sane · Dec 7th, 2005, 6:57 PM

What's the difference between those two sets of includes?

And in what context are there different character sets? =O

UnKnown X · Dec 7th, 2005, 6:59 PM

There's the EBCDIC set used by some computers

I don't really know a more efficient way for performing character checks than to write a function that takes a character as an argument and returns c == 'A' || c == 'B' || ... || c == 'Z' where c is that character.

Unless of course you use the isalpha function from the standard string library.

nnxion · Dec 7th, 2005, 7:01 PM

There is also EBCDIC. But I think you don't have to worry about that in *nix and windows worlds, since they use ascii and unicode.

Edit: Need to type faster

Sane · Dec 7th, 2005, 7:03 PM

Ah I see.

And by the way, this is why I love Python.

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return''.join(chr((ord(k[a%len(k)])+ord(t[a]))%26+65)for a in range(len(t)))

So much shorter then that C++ code. XD

EDIT: Oh, and thanks Ooble! I'll try that. Nice Avatar too.

Munsta · Dec 7th, 2005, 8:39 PM

EBCDIC charset is used on IBM mainframes but you shouldn't worry about that because they don't run Windows or *nix.

DaWei · Dec 7th, 2005, 8:41 PM

Quote:

So much shorter then that C++ code. XD

Of course, you're enjoying riding on someone else's shoulders (nothing wrong with that, either). There's a hell of a lot of C/C++ code behind that, helping you out.

Dec 7th, 2005, 5:30 PM	#1
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 2,075 Rep Power: 6	My First C++ Program I need to learn C++ for school soon, so I thought I'd get started sooner with a quick script. This demonstrates the Vigenere Cypher, nothing too deep in the code. It's only heavily commented because I had to sell it. (Toggle Plain Text) #include <iostream> #include <fstream> #include <stdlib.h> #include <string.h> using namespace std; string Qualify(string text) // this will get rid of all non A-Z letters { string result (""); // the result of the function int lp, let_val; // the loop indicator, and ascii value var strupr((char ) text.c_str()); // convert all characters to upper case for(lp = 0; lp < text.length(); lp++) // loop through every character in 'text' { let_val = int(text[lp]); // get the ascii value of the letter if (let_val > 64 && let_val < 91) // if the letter is between 'A' and 'Z' { result += text[lp]; // keep this letter } } return (result); // give back the result } string VigenereCypher(string text, string key) // this encrypts a string into a Vigenere Cypher { string result (""); // the result of our function text = Qualify(text); // remove the spaces and upper-case 'text' key = Qualify(key); // same to the 'key' int key_len(key.length()), lp, let_val, key_val; // declared our variables for(lp = 0; lp < text.length(); lp++) // loop through each character in 'text' { let_val = int(text[lp]); // get the ascii value of the letter key_val = int(key[lp % key_len]); // get the ascii value of our current key letter / basically, the Vigenere Cypher changes the value of the current letter by an amount equal to the current letter of the key, so to do this we must: - add the two values together and subtract by 130 to get a value from 0-50, - confine the result to 0-25 by finding the remainder (%) of dividing by 26, - add the number to 65, because 65 = A, 66 = B, etc, - convert to ascii, then append to result / result += char((let_val + key_val - 130) % 26 + 65); } return (result); // give back the result } int main () { string cypher, key, text; // declare variables cout << "Enter the text (no spaces): "; // no spaces allowed in cin cin >> text; // get text from user cout << "Enter the key: "; cin >> key; // get key from user cypher = VigenereCypher(text, key); // using the text and key, get cypher ofstream ofile; ofile.open ("VigenereCyphers.txt", ofstream::out \| ofstream::app); ofile << "Text:\n - " << text << "\nKey:\n - " << key << "\nCypher:\n - " << cypher << "\n\n"; ofile.close(); // appended all data to a text file cout << cypher << endl; // display the cypher cout << "\nAppended to: VigenereCyphers.txt" << endl; system("PAUSE"); // wait for the user to press a key return 0; } #include <iostream> #include <fstream> #include <stdlib.h> #include <string.h> using namespace std; string Qualify(string text) // this will get rid of all non A-Z letters { string result (""); // the result of the function int lp, let_val; // the loop indicator, and ascii value var strupr((char ) text.c_str()); // convert all characters to upper case for(lp = 0; lp < text.length(); lp++) // loop through every character in 'text' { let_val = int(text[lp]); // get the ascii value of the letter if (let_val > 64 && let_val < 91) // if the letter is between 'A' and 'Z' { result += text[lp]; // keep this letter } } return (result); // give back the result } string VigenereCypher(string text, string key) // this encrypts a string into a Vigenere Cypher { string result (""); // the result of our function text = Qualify(text); // remove the spaces and upper-case 'text' key = Qualify(key); // same to the 'key' int key_len(key.length()), lp, let_val, key_val; // declared our variables for(lp = 0; lp < text.length(); lp++) // loop through each character in 'text' { let_val = int(text[lp]); // get the ascii value of the letter key_val = int(key[lp % key_len]); // get the ascii value of our current key letter /* basically, the Vigenere Cypher changes the value of the current letter by an amount equal to the current letter of the key, so to do this we must: - add the two values together and subtract by 130 to get a value from 0-50, - confine the result to 0-25 by finding the remainder (%) of dividing by 26, - add the number to 65, because 65 = A, 66 = B, etc, - convert to ascii, then append to result */ result += char((let_val + key_val - 130) % 26 + 65); } return (result); // give back the result } int main () { string cypher, key, text; // declare variables cout << "Enter the text (no spaces): "; // no spaces allowed in cin cin >> text; // get text from user cout << "Enter the key: "; cin >> key; // get key from user cypher = VigenereCypher(text, key); // using the text and key, get cypher ofstream ofile; ofile.open ("VigenereCyphers.txt", ofstream::out \| ofstream::app); ofile << "Text:\n - " << text << "\nKey:\n - " << key << "\nCypher:\n - " << cypher << "\n\n"; ofile.close(); // appended all data to a text file cout << cypher << endl; // display the cypher cout << "\nAppended to: VigenereCyphers.txt" << endl; system("PAUSE"); // wait for the user to press a key return 0; } And I realise there's some "bad form", like system("PAUSE"). But I couldn't do cin.get(), because after the user hits enter from the last cin, it seems to carry through over to cin.get(). Oh well, wee.

Dec 7th, 2005, 5:36 PM	#2
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Noice. BTW, try: (Toggle Plain Text) cin.sync(); // clears the input buffer (apparently) cin.get(); cin.sync(); // clears the input buffer (apparently) cin.get(); __________________ Me :: You :: Them

Dec 7th, 2005, 5:57 PM	#3
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 648 Rep Power: 4	And just for future reference, a C++ program is not a script __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

Dec 7th, 2005, 6:56 PM	#4
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	Not bad for a first try. You should use <cstdlib> and <string> instead of <stdlib.h> and <string.h>. Using namespace std is also (often) not good practice. Instead try: using std::cout; etc. You also know that you are relying on the ascii character set here, and that other character sets might not have A at 65. __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Dec 7th, 2005, 7:01 PM	#7
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	There is also EBCDIC. But I think you don't have to worry about that in *nix and windows worlds, since they use ascii and unicode. Edit: Need to type faster __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Dec 7th, 2005, 6:57 PM	#5
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 2,075 Rep Power: 6	What's the difference between those two sets of includes? And in what context are there different character sets? =O

Dec 7th, 2005, 6:59 PM	#6
UnKnown X Hobbyist Programmer Join Date: Dec 2005 Location: Sandvika, Norway Posts: 114 Rep Power: 0	There's the EBCDIC set used by some computers I don't really know a more efficient way for performing character checks than to write a function that takes a character as an argument and returns c == 'A' \|\| c == 'B' \|\| ... \|\| c == 'Z' where c is that character. Unless of course you use the isalpha function from the standard string library.

Dec 7th, 2005, 7:03 PM	#8
Sane Programming Guru Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 2,075 Rep Power: 6	Ah I see. And by the way, this is why I love Python. (Toggle Plain Text) return''.join(chr((ord(k[a%len(k)])+ord(t[a]))%26+65)for a in range(len(t))) return''.join(chr((ord(k[a%len(k)])+ord(t[a]))%26+65)for a in range(len(t))) So much shorter then that C++ code. XD EDIT: Oh, and thanks Ooble! I'll try that. Nice Avatar too.

Dec 7th, 2005, 8:39 PM	#9
Munsta Newbie Join Date: Nov 2005 Posts: 9 Rep Power: 0	EBCDIC charset is used on IBM mainframes but you shouldn't worry about that because they don't run Windows or *nix.

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My First C++ Program