custom string exercise in c++

Question

I have a custom string class that uses an array of chars,

class MyString
{

private:
int length; 
char *chars; 

public:
MyString(const char* input)
{
    length = 0; 
    while (input[length] != '\0')
        ++length;

    chars = new char[length + 1];

    for (int j = 0; j < length; j++)
        chars[j] = input[j];
}

However when I use this class with a simple output I am getting a strange result in the console:

MyString newStr = "Test";
cout << newStr;

Gives me this output in the console:

Test═²²²²½½½½½½½½■ε■ε■ε■

This is with Visual Studio 2010 Win32 console app. I don't really know c++ very well and this is my first try at it.

Your first try should be with a [book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list), do you have one? — GManNickG, Jan 18 '11 at 02:20
You haven't shown the code that outputs the string. Show that. — Cheers and hth. - Alf, Jan 18 '11 at 02:34

score 2 · Answer 1 · answered Jan 18 '11 at 02:22

2

You forgot to put \0 at the end of chars[]. \0 is the character that MUST be put at the end of a char sequence. Otherwise, your program will output some random stuff (the bits after your array in memory) until it finds a \0.

answered Jan 18 '11 at 02:22

Hilydrow

918
1
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score 2 · Answer 2 · answered Jan 18 '11 at 02:24

2

Your loop that copies input to chars isn't including the NUL terminator. Change the loop condition to j <= length and it should work.

answered Jan 18 '11 at 02:24

Daniel Gallagher

6,915
25
31

score 1 · Answer 3 · answered Jan 18 '11 at 02:23

1

There are a couple of things that I'd recommend:

You are not null terminating your chars[]
you need to overload the << operator. Go to: http://www.fredosaurus.com/notes-cpp/oop-friends/overload-io.html for an example.

answered Jan 18 '11 at 02:23

David Weiser

5,190
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custom string exercise in c++

3 Answers3

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