I am doing this
char *draw_line(int n, char ch)
{
char *line = new char[50];
for(int i = 0; i <= n; i++)
line[i] = ch;
return line;
}
and while calling the function I am writing this:
char *res_line = draw_line(50, '=');
cout<<*res_line;
but instead of getting = printed 50 times in the console window, it just show = sign one time. My main aim is to return the = or any character as many times I want and output
the same to a text file. That's it.
cout<<*res_line;
is printing one char because *res_line is char, not char*.
Write:
cout<<res_line;
But wait — that is not going to work either because res_line is NOT null-terminated.
Use std::string or std::vector<char> — avoid explicit memory allocation, use RAII idiom instead:
std::string draw_line(int n, char ch)
{
return {n, ch}; //C++11
}
So simple!
Or if you use std::vector:
std::vector<char> draw_line(int n, char ch)
{
return {n, ch}; //C++11
}
which is almost same.
In C++03, however, you've to write:
return std::string(n, ch); //in the first case
return std::vector<char>(n, ch); //in the second case
That is, invoke the constructor explicitly.
draw_line is not null terminated. (You should probably put that in your answer.)
std::vector. std::string is just as good because it is element-wise accessible in the same way vector is, plus it is made to be used with characters.The valid code will look as
char* draw_line( int n, char ch )
{
char *ch2= new char[n + 1]();
std::memset( ch2, ch, n );
return ch2;
}
//...
char *ch50 = draw_line(50,'=');
cout << ch50;
//...
delete []ch50;
Take into account this statement
char *ch2= new char[n + 1]();
But it would be much better to write simply
std::cout << std::string( 50, '=' );
char* draw_line(int n, char ch)
{
char *ch2= (char *) malloc(sizeof(char)*(n+1)); // (n+1) here
for(int i=0;i<n;i++) // < instead of <=
ch2[i]=ch;
ch2[n] = 0; // terminator
return ch2;
}
char *ch50 = draw_line(50,'=');
cout<< ch50; // changed from *ch50 to ch50
ADDON: look at string-fill constructor
cout << string(50, '=');
std::stringnand50are secretly related, you're right. once you fix the terminator, trycout << ch50. And plz consider just usingstd::string(50,ch). Use the standard lib. It's whats for dinner.std::stringbecause it can be safer and more versatile (and because C++ standard); however, if you want to use char[] or char*, then more power to you in my opinion. It just means you may run into more problems to overcome. A learning experience, if you ask me.std::stringis that it won't leak memory. (Of course, if he can accept a maximumn, it's possible to write a thread safe version using a static variable, and avoid all dynamic allocation completely.)