Create string with specified number of characters

Question

Is there a way to create a string of say 256 characters at initialization with c++?

Part of my assignment requires me to "1. Create a string of 256 characters. Use repetitions of your first name."

I'm not quite sure of how to do this other than using a loop but I feel like there is an easier way.

Answer 1

Taking a look at the constructor reference of basic_string, one can see that there is no easy way of repeating a complete string. For a single character, you could use (2) like this:

std::string s(5, 'a'); // s == "aaaaa" 

For generating a string repetition, you'll need some workaround. It's easier to do this post-construction by simply filling the string with, for example, std::generate (having fun with algorithms).

#include <string> #include <algorithm>  // ...  std::string pattern("Xeo "); auto pattern_it = pattern.begin(); std::string s(256, '\0'); std::generate(s.begin(), s.end(),     [&]() -> char {        if(pattern_it == pattern.end())         pattern_it = pattern.begin();       return *pattern_it++; // return current value and increment     }); 

Live example.

Answer 2

If you want a very long string, you can cut down the number of loop repetitions by doubling.

#include <string> using std::string;  string repeatToLength ( unsigned len, string s ) {   string r, si = s;    // add all the whole multiples of s.   for ( unsigned q = len / s.size(); q > 0; q >>= 1 ) {     if ( q & 1 ) r += si; // add si to r if the low bit of q is 1     si +=  si; // double si   }   r += s.substr ( 0, len - r.size() ); // add any remainder   return r; }