std::list and STL containers

Dr. Lawlor, CS 202, CS, UAF

std::list is useful to store a list of objects, where you need to both add and remove objects from the list. Unlike vector, it's efficient to add new elements to the middle of a list. Here's the basic interface, which looks extremely similar to std::vector:

#include <list>

int foo(void) {
	std::list<string> l;
	l.push_back("alphonse");
	l.push_back("denise");
	l.push_back("charlie");
	cout<<"List's front == "<<l.front()<<"\n";
	cout<<"List's back == "<<l.back()<<"\n";
	return 0;
}

(Try this in NetRun now!)

The way you access the elements of a list is with an "iterator", which acts like a pointer into the list. You move the iterator forward with "++it", and dereference the iterator with "*it". The iterator starts at "l.begin()", and runs all the way until it hits "l.end()". Typically these are combined into a very weird looking for loop, like so:

#include <list>

int foo(void) {
	std::list<string> l;
	l.push_back("alphonse");
	l.push_back("denise");
	l.push_back("charlie");
	for (std::list<string>::iterator it=l.begin();it!=l.end();++it)
		cout<<"List contains "<<*it<<"\n";
	return 0;
}

(Try this in NetRun now!)

This prints out the contents of the list, one at a time.

Lists support a surprising range of features. Here are some of the more surprising features:

push_back adds an element at the end. push_front adds an element at the beginning.
"l.sort();" sorts the list. "l.reverse();" reverses the order of the list.
"l.splice(it,other);" inserts elements from another list at a given location.
"l.remove("denise");" erases elements by value.

Lists are definitely something to keep in your toolbox!