Build your own algorithm: split

The STL has a rich algorithm library. Yet, on occasion you may find it missing something you need. One common need is a split function.

A split function splits a string on a character separator. For example, here's a Unix /etc/passwd file from a standard Debian installation:

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync

Each field is separated by a colon : character, where the fields are:

1. Login name
2. Optional encrypted password
3. User ID
4. Group ID
5. Username or comment
6. Home directory
7. Optional command interpreter

This is a standard file in POSIX-based operating systems, and there are others like it. Most scripting languages include a built-in function for splitting a string on a separator. There are simple ways to do this in C++. Still, std::string is just another...