Overloading operators such as <<,>>,== etc.

George Porter

Hi, I have a problem to solve and I really don't know where to start. Here is the problem:

Implement a class that does string manipulation by overloading the following operators: <<, >>, = and ==. For example consider the following code:

StrShift example;
example = "John";
printf("\"example << 2\" results in %s\n", example << 2);

In the above code the output would be "hnJo" which shows the last two characters of the string "John" rotated to the left of the string. Please note that state is maintained so two calls of example << 1 would give the same end result as calling example << 2 once.

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
Sorry, George, there was an error in the RotateRight method which I've corrected now in the original post.

I've also expanded the examples to include testing of the >> and != operator overloads.

Incidentally, one thing I forgot to mention previously is that when the question says that 'state should be maintained' I've taken it that the instance of StrShift being operated on should be mutated so that its underlying string represents the result of the operation.

This isn't something that would normally be done in C# because strings themselves are immutable though it is possible to achieve.
0
SUNIL GUTTA12y ago
Nice lines george :) I too wanna become like him and share the knowledge i attain to my beloved friends . Vulpes Ty very much for sharing your thoughts & Time . Words cant appreciate your effort .

Have a nice day
0
George Porter12y ago
Dear Vulpes, I cannot thank you enough for all your help. You are great person.
0
George Porter12y ago
Dear Friend, There is a problem with the code above. The >> operators return a strange thing, for example John >> 2 returns Jnnn
0
George Porter12y ago
Dear friend, thank you very much for taking the time and effort to answer this question. I wish one day that I will be a great Engineer like you and give back to you and the community all the knowledge and help that you offered me. Thank you so much.
0
Vulpes12y ago
Well, first of all, you can't overload the assignment operator '=' in C#. However, you can create an implicit conversion from string to StrShift which is just as good as far as this example is concerned.

Notice also that if you overload '==' then you have to overload '!=' as well. It's also good practice to overload the GetHashCode and Equals methods which StrShift will inherit from System.Object at the same time.

Finally, note that the C function printf is not supported in C# - you have to use Console.Write(Line) instead. Incidentally, operator overloading is not permitted in C at all though it is permitted in C++.

Anyway here's some C# code to do all this:

using System;

public class StrShift
{
private string str;

public StrShift(string str)
{
this.str = str;
}

public static implicit operator StrShift(string s)
{
return new StrShift(s);
}

public override string ToString()
{
return str;
}

public override int GetHashCode()
{
return str.GetHashCode();
}

public override bool Equals(object obj)
{
return str.Equals(obj);
}

public static bool operator ==(StrShift ss1, StrShift ss2)
{
return ss1.str == ss2.str;
}

public static bool operator !=(StrShift ss1, StrShift ss2)
{
return ss1.str != ss2.str;
}

public static StrShift operator <<(StrShift ss, int n)
{
if (n < 1) return ss;
char[] chars = ss.str.ToCharArray();
for(int i = 1; i <= n; i++) RotateLeft(chars);
ss.str = new string(chars); // maintain state
return ss;
}

public static StrShift operator >>(StrShift ss, int n)
{
if (n < 1) return ss;
char[] chars = ss.str.ToCharArray();
for(int i = 1; i <= n; i++) RotateRight(chars);
ss.str = new string(chars); // maintain state
return ss;
}

private static void RotateLeft(char[] chars)
{
int len = chars.Length;
if (len < 2) return;
char temp = chars[0];

for(int i = 1; i < len; i++)
{
chars[i - 1] = chars[i];
}

chars[len - 1] = temp;
}

private static void RotateRight(char[] chars)
{
int len = chars.Length;
if (len < 2) return;
char temp = chars[len - 1];

for(int i = len - 2; i >= 0; i--)
{
chars[i + 1] = chars[i];
}

chars[0] = temp;
}
}

class Program
{
static void Main()
{
StrShift example = "John";
Console.WriteLine("\"example << 2\" results in {0}\n", example << 2);
StrShift example2 = "John"; // set to original value
Console.WriteLine("\"example2 << 1\" results in {0}", example2 << 1);
Console.WriteLine("and \"example2 << 1\" again results in {0}\n", example2 << 1);
Console.WriteLine("\"example == example2\" is {0}\n", example == example2);
example = "John"; // reset to original value
Console.WriteLine("\"example >> 2\" results in {0}\n", example >> 2);
example2 = "John"; // set to original value
Console.WriteLine("\"example2 >> 1\" results in {0}", example2 >> 1);
Console.WriteLine("and \"example2 >> 1\" again results in {0}\n", example2 >> 1);
Console.WriteLine("\"example != example2\" is {0}", example != example2);
Console.ReadKey();
}
}

The output is:

"example << 2" results in hnJo

"example2 << 1" results in ohnJ
and "example2 << 1" again results in hnJo

"example == example2" is True

"example >> 2" results in hnJo

"example2 >> 1" results in nJoh
and "example2 >> 1" again results in hnJo

"example != example2" is False

0