Convert sentence to morse code

earachefl · #1 01-May-2006, 14:56

This code is to convert a sentence into Morse code. The run log always terminates with error:

Quote:

Enter a sentence to be translated to Morse Code:
Hi
....
..
terminate called after throwing an instance of 'std:

ut_of_range'
what(): basic_string::at

C9PP9 has exited due to signal 6 (SIGABRT).

TIA for your help!!!

CPP / C++ / C Code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#define inFile "/Users/me/Documents/COMSCI101/C9PP9/MorseCode.txt"    //define location for MorseCode.txt

//function prototypes
void readCode (ifstream&, string[]);
void writeCode (const string[], const char);

int main () 
{
    string codeArray[26];   //Storage for Morse code characters read from codeFile
    string sentence;        //Input - next word
    char nextChar;          //Storage for next character read from string sentence
    int i;                  //counter variable
    ifstream codeFile (inFile); //Declare ifstream codeFile, associate with and open inFile
    if (codeFile.fail()) {
        cerr << "Error opening Code file" << endl;
        return EXIT_FAILURE;
    }
    
    readCode (codeFile, codeArray); //call function readCode to read each code into codeArray
    
    cout << "Enter a sentence to be translated to Morse Code: " << endl;
    cin >> sentence;
    while (sentence != ".") {   //while a period is not entered
        i = 0;                  //initialize counter i
        
        //cout << "< At beginning of outer while loop, i is " << i ;  //uncomment for error checking
        
        nextChar = sentence.at(i);  //get each character in turn from string sentence
        
        //cout << ", and nextChar is " << nextChar << " >" << endl;     //uncomment for error checking
        
        nextChar = toupper(nextChar);   //convert all lowercase characters to uppercase
        
        while (nextChar != ' ') {               //while blank space is not encountered
            writeCode (codeArray, nextChar);    //call function writeCode to display Morse code for nextChar
            i++;                                //increment counter i
            nextChar = sentence.at(i);          //get next character from string sentence
            
            //cout << "<< In inner while loop, nextChar is " << nextChar << ">>" << endl; //Uncomment for error checking
            
            if (nextChar == ' ') {              //if blank space is read, 
                break;                          //break out of loop
            }   
            nextChar = toupper(nextChar);       //convert lowercase to uppercase
        }
        cout << endl;
    }
    codeFile.close();
    
    return 0;
}

//Stores Morse codes read from codeFile in array code
void readCode (ifstream& codeFile, string codeArray[])
{
    int i;                      //counter variable
    string nextCode;            //storage for next code in file
    for (i = 0; i < 26; i++) {  //store strings from codeFile into codeArray
        codeFile >> nextCode;
        codeArray[i] = nextCode;
        
        //cout << nextCode << endl ;//uncomment to see contents of codeFile displayed
    }
}

//Writes Morse equivalent for a letter
void writeCode (const string codeArray[], const char letter)
{
    //cout << "<<< function writeCode called with character " << letter << ">>>" << endl; //uncomment for error checking
    //cout << "<<< integer value passed to codeArray is " << (int) letter - (int) 'A' << " >>>" << endl; //uncomment for error checking
    cout << codeArray[letter - (int) 'A'];  //display value of codeArray at location 0 - 25
    cout << " ";    //Display space between code
    //cout << endl;
}

QED · #2 01-May-2006, 15:01

The only terminal conditions I see in your loops are a check for '.' and a check for ' '. If your string ends in anything else (which I expect is the case, since newline is likely the last thing read in), then you will keep read characters past the end of the string, hence the index counter i will cause string::at() to throw an exception.

Matthew

earachefl · #3 01-May-2006, 21:17

(Edit) I've worked it out while writing this post - but am still interested in feedback on my solution)

OK, I'm still having a brain freeze on this. Help me break it down.

If I get a word from an input stream:

CPP / C++ / C Code:

cout << "Enter a sentence to be translated to Morse Code: " << endl;
 while (cin >> sentence) {   //while newline is not encountered, extract next word

And enter:

Quote:

Hi

followed by the newline character, the extraction operation grabs "Hi" , assigns it to variable sentence, ignores the newline character, and positions the input buffer pointer at the next character, right?
Now, if I was assigning "Hi" to a C-style string (character array), there would actually be three characters assigned, 'H', 'i', '\0'. But since I'm using a C++ string, there are only the two characters in the string, as evidenced by using

CPP / C++ / C Code:

cout << "sentence string length is: " << sentence.length() << endl;

and run log shows :

Quote:

Enter a sentence to be translated to Morse Code:
Hi
sentence string length is: 2

So having gotten that out of the way, and using input "Hi" as an example, using loop repetition condition

CPP / C++ / C Code:

while (nextChar = sentence.at(i))

should cause the loop to execute only twice. Both times it should call function writeCode with the current character (causing the corresponding Morse code to be displayed), increment the counter, and test the loop repetition condition. After the second repetition, the condition should fail, the loop should not execute, and control should return to the outer while loop, awaiting input from the keyboard.

The problem in my code is that

CPP / C++ / C Code:

while (nextChar = sentence.at(i))

doesn't actually cause the loop to terminate because the C++ string has no terminating null character, so it's not a valid loop termination condition, and the program tries to read from the string array at an out-of-bounds position. So my immediate thought would be to get the string length each time and use that as the termination condition. And indeed that works.

The complete (revised) code of that section is:

CPP / C++ / C Code:

cout << "Enter a sentence to be translated to Morse Code: " << endl;

    while (cin >> sentence) {   //while newline is not encountered, extract next word
        i = 0;                  //initialize counter i
        int length;            //Variable to store word length
        length = sentence.length(); //get length of sentence, store in variable length
        while (i < length) {   //while counter is less then the length of the word
            nextChar = sentence.at(i);//get each character in the word
            nextChar = toupper(nextChar);  //convert lower to upper case
            if (nextChar == '.') {   //If sentence ends in period, break out of loop
                break;
            }
            writeCode (codeArray, nextChar);    //call function writeCode to display Morse code for nextChar
            i++;                                //increment counter i
            }
        cout << endl;
    }

I still have a little work to do, but that's basically working.
Is that the "best" solution given the low level of programming that I'm on?

WaltP · #4 02-May-2006, 00:14

Instead of reading one word at a time, read the entire sentence with getline(). This will allow you to process whitespace (TABs and SPACEs) more accurately.

Also, why stop when you get a '.'? A period is a valid Morse Code character. IMO, you should process all valid characters and either ignore or flag all invalid characters.

QED · #5 02-May-2006, 07:29

It might help to consider that std::string is an STL container (of chars). This means that you can use iterators to traverse the string. It is similar to what you've got already, except that each time you call string::at() bounds-checking is performed (some might say unnecessarily, since you know the length of the string).

CPP / C++ / C Code:

cout << "Enter a sentence to be translated to Morse Code: " << endl;

    while (cin >> sentence) {   //while newline is not encountered, extract next word
        std::string::const_iterator pos;
        for (pos = sentence.begin(); pos != sentence.end(); ++pos)
        {   // while current position is within the string
            nextChar = toupper(*pos);  // get current char and convert to upper case
            if (nextChar == '.') {   //If sentence ends in period, break out of loop
                break;
            }
            writeCode (codeArray, nextChar);    //call function writeCode to display Morse code for nextChar
        }
        cout << endl;
    }

Matthew

earachefl · #6 02-May-2006, 09:53

Quote:

Originally Posted by WaltP

Instead of reading one word at a time, read the entire sentence with getline(). This will allow you to process whitespace (TABs and SPACEs) more accurately.

Also, why stop when you get a '.'? A period is a valid Morse Code character. IMO, you should process all valid characters and either ignore or flag all invalid characters.

Walt, that was the assignment! I guess the authors decided that having beginners deal with 26 contiguous characters was a heck of a lot easier than having to deal with some 52 or 53 non-contiguous ones, not counting the special characters.

WaltP · #7 02-May-2006, 17:02

Quote:

Originally Posted by earachefl

Walt, that was the assignment! I guess the authors decided that having beginners deal with 26 contiguous characters was a heck of a lot easier than having to deal with some 52 or 53 non-contiguous ones, not counting the special characters.

OK. It might help to review Guideline 4 for next project.

earachefl · #8 02-May-2006, 17:04

Quote:

Originally Posted by WaltP

OK. It might help to review http://www.gidforums.com/t-5566.html for next project.

Will do, sorry.

#9 03-May-2006, 07:39

Morse.h

CPP / C++ / C Code:

#ifndef _Morse_h_
#define _Morse_h_

#include <iostream>
#include <string>
#include <map>
#include <cstring>

using namespace std;

typedef std::map<char, std::string>mapMorseCode;

class Morse
{
public:
    Morse();
    void print_char_to_code( const char c );
private:
    void init();
    mapMorseCode m_mapMorseCode;
};

#endif // ! _Morse_h_

Morse.cpp

CPP / C++ / C Code:

#ifndef _Morse_h_
#include <Morse.h>
#endif
Morse::Morse()
{
    init();
}

void
Morse::init()
{
    m_mapMorseCode.insert( pair<char,std::string>( 'A', ".-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'B', "-..." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'C', "-.-." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'D', "-.." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'E', "." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'F', "..-." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'G', "--." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'H', "...." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'I', ".." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'J', ".---" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'K', "-.-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'L', ".-.." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'M', "--" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'N', "-." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'O', "---" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'P', ".--." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'Q', "--.-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'R', ".-." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'S', "..." ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'T', "-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'U', "..-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'V', "...-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'W', ".--" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'X', "-..-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'Y', "-.--" ) );
    m_mapMorseCode.insert( pair<char,std::string>( 'Z', "--.." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '.', ".-.-.-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( ',', "-..--" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '?', "..--.." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '0', "-----" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '1', ".----" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '2', "..---" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '3', "...--" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '4', "....-" ) );
    m_mapMorseCode.insert( pair<char,std::string>( '5', "....." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '6', "-...." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '7', "--..." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '8', "---.." ) );
    m_mapMorseCode.insert( pair<char,std::string>( '9', "----." ) );
    m_mapMorseCode.insert( pair<char,std::string>( ' ', "_" ) );

}

void 
Morse::print_char_to_code( const char c )
{
    char l = c;
    if( isalpha( c ) )
    {
        l = toupper( c );
    }
    try
    {
        cout << m_mapMorseCode.find( l )->second;
    }
    catch( ... )
    {

    }
}

int main()
{
    Morse m;
    std::string str = "The quick brown fox jumps over the lazy dog.";
    for( int i = 0; i < (int)str.size(); i++ )
    {
        cout << str[i] << " = ";
        m.print_char_to_code( str[i] );
        cout << endl;
    }
    return 0;
}

Output:

Code:

T = -
h = ....
e = .
  = _
q = --.-
u = ..-
i = ..
c = -.-.
k = -.-
  = _
b = -...
r = .-.
o = ---
w = .--
n = -.
  = _
f = ..-.
o = ---
x = -..-
  = _
j = .---
u = ..-
m = --
p = .--.
s = ...
  = _
o = ---
v = ...-
e = .
r = .-.
  = _
t = -
h = ....
e = .
  = _
l = .-..
a = .-
z = --..
y = -.--
  = _
d = -..
o = ---
g = --.
. = .-.-.-

...I used an underscore for spaces, since in Morse code, a space is simply a pause in transmission of characters. This is a rather quick and dirty hack, but should give you an idea of at least one alternative that flexes C++ standard library features a bit more along the lines of what Matthew noted previously.

By changing the input string:

Code:

A = .-
B = -...
C = -.-.
s = ...
  = _
a = .-
r = .-.
e = .
  = _
a = .-
s = ...
  = _
s = ...
i = ..
m = --
p = .--.
l = .-..
e = .
  = _
a = .-
s = ...
  = _
1 = .----
2 = ..---
3 = ...--
. = .-.-.-

...obviously a more robust class implementation would handle unknown characters better and offer much better interfaces for conversion to and from Morse code, etc.

:davis:

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