For every character in string

Question

1. Looping through the characters of a std::string, using a range-based for loop (it's from C++11, already supported in recent releases of GCC, clang, and the VC11 beta):

   std::string str = ???;
   for(char& c : str) {
       do_things_with(c);
   }
   

2. Looping through the characters of a std::string with iterators:

   std::string str = ???;
   for(std::string::iterator it = str.begin(); it != str.end(); ++it) {
       do_things_with(*it);
   }
   

3. Looping through the characters of a std::string with an old-fashioned for-loop:

   std::string str = ???;
   for(std::string::size_type i = 0; i < str.size(); ++i) {
       do_things_with(str[i]);
   }
   

4. Looping through the characters of a null-terminated character array:

   char* str = ???;
   for(char* it = str; *it; ++it) {
       do_things_with(*it);
   }
   

A for loop can be implemented like this:

string str("HELLO");
for (int i = 0; i < str.size(); i++){
    cout << str[i];
}

This will print the string character by character. str[i] returns character at index i.

If it is a character array:

char str[6] = "hello";
for (int i = 0; str[i] != '\0'; i++){
    cout << str[i];
}

Basically above two are two type of strings supported by c++. The second is called c string and the first is called std string or(c++ string).I would suggest use c++ string,much Easy to handle.

In modern C++:

std::string s("Hello world");

for (char & c : s)
{
    std::cout << "One character: " << c << "\n";
    c = '*';
}

In C++98/03:

for (std::string::iterator it = s.begin(), end = s.end(); it != end; ++it)
{
    std::cout << "One character: " << *it << "\n";
    *it = '*';
}

For read-only iteration, you can use std::string::const_iterator in C++98, and for (char const & c : s) or just for (char c : s) in C++11.

Here is another way of doing it, using the standard algorithm.

#include <iostream>
#include <string>
#include <algorithm>

int main()
{
   std::string name = "some string";
   std::for_each(name.begin(), name.end(), [] (char c) {
      std::cout << c;
   });
}

const char* str = "abcde";
int len = strlen(str);
for (int i = 0; i < len; i++)
{
    char chr = str[i];
    //do something....
}

I don't see any examples using a range based for loop with a "c string".

char cs[] = "This is a c string\u0031 \x32 3";

// range based for loop does not print '\n'
for (char& c : cs) {
    printf("%c", c);
}

not related but int array example

int ia[] = {1,2,3,4,5,6};

for (int& i : ia) {
    printf("%d", i);
}