copy string

[atlkhan]

Hi I have this simple program which copies one string to another i.e newstring---->old . When I print out old string it is succesfully copied. But when I use a program to test if those two strings are equal, It gives me false value. Can someone guide me. I think it has something to do with how I allocate memory.

Here is my program


#include<iostream>
#include<string>
using namespace std;
int main()
{
char *newstring="This is the string I want to copy into old";
char *old;
char test='a';
int index=0;
bool result;

// Copying newstring to the old string

old = new char[100] ;
while(test != '\0')
{



old[index]=newstring[index];
test=old[index];
index=index+1;


}

// Testing if the old string is equal to the newstring

test='a';

while(test != '\0')
{
test=newstring[index];

if(newstring[index] == old[index])
result = true;
else
{
result=false;
break;
}
index =index+1;
}

//Checking the result of comparision

cout<<"\n The result is "<<result<<endl;

}

[Savage]

old = new char[100] ;
while(test != '\0')
{
   old[index]=newstring[index];
   test=old[index];
   index=index+1;
}

There is a simple function declared in string.h called strcat which appends one string to the end of another.So if we set old[0] to '\0' and then call the function we will sucsessfully copy one string to another.If u wish to test it there is also a nice function called strcmp which tests strings and return 0 if they match.

Savage

[JosAH]

old = new char[100] ;
while(test != '\0')
{
   old[index]=newstring[index];
   test=old[index];
   index=index+1;
}

There is a simple function declared in string.h called strcat which appends one string to the end of another.So if we set old[0] to '\0' and then call the function we will sucsessfully copy one string to another.If u wish to test it there is also a nice function called strcmp which tests strings and return 0 if they match.

Savage

There's another simple function for copying a string: strcpy(). You don't have to
manually set the first char to '\0' then. The reason of failing to compare those
two strings succesfully is the fact that variable 'index' isn't reset to 0 (zero)
before the comparing while loop starts.

kind regards,

Jos

[atlkhan]

Thanks man , I really appreciate it