reverse the string

This is a discussion on reverse the string within the C++ Programming forums, part of the General Programming Boards category; For my driver I have to reverse the strings in a string literal by means of a class called ReverseString. ...

  1. #1
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    reverse the string

    For my driver I have to reverse the strings in a string literal by means of a class called ReverseString. I will show you guys my function below that is supposed to reverse my string. I will also post my test for the string. My output is:
    ahsuruP
    ahsuruP
    ahsuruP

    and I am pretty sure that is not the correct output. Why doesn't my function work? Thanks for the help

    Code:
    ReverseString ReverseString::operator ~()
    {
    	int k = 0;
    	char *temp = buf;
    	for(int i = stringlength-1; i>=(stringlength/2); i--)
    	{
    		swap(temp[k], temp[i]);
    		k++;	
    	}
    	return temp;
    }
    
    
    void test19() {
    
        system("cls");
    
        cout << "19. Testing: ReverseString class." << endl << endl;
    
        csis << "19. Testing: ReverseString class." << endl << endl;
    
        ReverseString s19("Purusha");
    
        ReverseString t19;
    
        s19.setName("s19");
    
        t19.setName("t19");
    
        t19 = ~s19;
    
        s19.print();
    
        t19.print();
    
     
    
        ReverseString u19(~~s19);
    
        u19.setName("u19");
    
        u19.print();
    
        wait();
    
    }

  2. #2
    System Novice siavoshkc's Avatar
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    Where is the class?
    Learn C++ (C++ Books, C Books, FAQ, Forum Search)
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  3. #3
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    Quote Originally Posted by siavoshkc View Post
    Where is the class?
    I posted the function (~operator) but I'll post the entire header and source code:

    Code:
    //reverse.h
    
    #ifndef ReverseString_H
    #define ReverseString_H
    
    #include <iostream>
    #include "string.h"
    #include "strdrv.h"
    
    
    
    
    
    class ReverseString: public String
    {
    public:
    	ReverseString();
    	ReverseString(const ReverseString &rhs);
    	ReverseString(const char *str);
    	ReverseString operator=(const ReverseString &rhs);
    	ReverseString operator~();
    };
    
    #endif
    
    // reverse.cpp
    #define _CRT_SECURE_NO_DEPRECATE 1	
    #include <iostream>
    #include <assert.h>
    #include <algorithm>
    #include "reverse.h"
    
    
    using namespace std;
    
    ReverseString::ReverseString()
    { }
    
    ReverseString::ReverseString(const ReverseString &rhs)
    { }
    
    
    ReverseString::ReverseString(const char *str)
    {
    	name = NULL;
    	assert( str != 0);
    	stringlength = strlen(str);
    	size = stringlength + 1;
    	buf = new char[size];
    	strcpy(buf, str);
    }
    
    ReverseString ReverseString::operator =(const ReverseString &rhs)
    {
    	if(this != &rhs)
    	{
    		delete []buf;
    		stringlength = rhs.stringlength;
    		size = stringlength + 1;
    		buf = new char[size];
    		strcpy(buf, rhs.buf);
    	}
    	return *this;
    }
    
    ReverseString ReverseString::operator ~()
    {
    	int k = 0;
    	char *temp = buf;
    	for(int i = stringlength-1; i>=(stringlength/2); i--)
    	{
    		swap(temp[k], temp[i]);
    		k++;	
    	}
    	return temp;
    }

  4. #4
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    Quote Originally Posted by BKurosawa View Post
    For my driver I have to reverse the strings in a string literal by means of a class called ReverseString. I will show you guys my function below that is supposed to reverse my string. I will also post my test for the string. My output is:
    ahsuruP
    ahsuruP
    ahsuruP

    and I am pretty sure that is not the correct output. Why doesn't my function work? Thanks for the help
    So what is the output you expect?

    Your operator~ does modifiy the original string which is probably not what you wanted...

    --
    Mats

  5. #5
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    Quote Originally Posted by matsp View Post
    So what is the output you expect?

    Your operator~ does modifiy the original string which is probably not what you wanted...

    --
    Mats
    I have the test up there. I might be wrong but I think that the output should be:
    Purusha
    ahsuruP
    Purusha

    How do I fix it? Thanks

  6. #6
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    What's the temp variable in your operator~ function? Where does it point, and how do you think you should fix it?

    --
    Mats

  7. #7
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    Quote Originally Posted by matsp View Post
    What's the temp variable in your operator~ function? Where does it point, and how do you think you should fix it?

    --
    Mats
    The temp points to buf... why is that a problem?

  8. #8
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    Quote Originally Posted by BKurosawa View Post
    The temp points to buf... why is that a problem?
    In you line "t19 = ~s19;", what is buf? What gets modified in that line?

    --
    Mats

  9. #9
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    Quote Originally Posted by matsp View Post
    In you line "t19 = ~s19;", what is buf? What gets modified in that line?

    --
    Mats
    What if I do this? :

    Code:
    ReverseString ReverseString::operator ~()
    {
    	int k = 0;
    	char *temp = buf;
    	for(int i = stringlength-1; i>=(stringlength/2); i--)
    	{
    		swap(temp[k], temp[i]);
    		k++;	
    	}
    	ReverseString object(temp);
    	return object;
    }

  10. #10
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    Sorry, but did you think that through, or just randomly guess ?

    No, that's not quite right, but you have the sort of right idea. The order in which you do things is a bit wrong, that's it.

    --
    Mats

  11. #11
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    >> The order in which you do things is a bit wrong.

    How so?

  12. #12
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    Instead of asking us to solve your coding problems, how about you think about what actually happens in the code... If you UNDERSTAND what you are doing, then it's going to work so much better for you in the future. You seem to prefer the method of "randomly change the code and hope that either it fixes the problem, or someone tells you how to do it" - this is NOT the right way to learn programming.

    --
    Mats

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