new ranges :D

iterators/main.cpp

@@ -1,21 +0,0 @@
-#include "counting_iterator.hpp"
-#include <vector>
-#include <iostream>
-
-int main(){
-	std::vector<int> v{1,3,37,1337,7};
-
-	for(auto x : counted(v)){
-		std::cout << "v[" << x.index << "] = " << x.value << std::endl;
-	}
-
-	for(auto x : counted(v)){
-		x.value *= x.index;
-	}
-
-	for(auto x : counted(v)){
-		std::cout << "v[" << x.index << "] = " << x.value << std::endl;
-	}
-
-	return 0;
-}

ranges/README.md

@@ -26,3 +26,18 @@ for(auto x : counted(v)) {
 ```
 This will output the container `v`, with it's indeces. And it will multiply every value in `v` by 2.
 
+
+tuple element
+=============
+
+```c++
+map<.., ..> m = {..};
+for(auto key : keys(m))
+	... key ...
+for(auto v : values(m))
+	... v ...
+```
+
+Some helper functions for easy access to maps. It also works well on vectors of tuples, or any container with a tuple-like interface.
+The general function is `nth_values<N>(v)`, which allows you to iterate over the N-th element in the tuples of `v`.
+For more information see tuple_element.h. Note that this does have a good const version, in contrast to the thing above (counted).

ranges/main.cpp

@@ -0,0 +1,50 @@
+#include <vector>
+#include <map>
+#include <iostream>
+
+#include "counting_iterator.hpp"
+#include "tuple_element.hpp"
+
+void counting_iterator(){
+	std::vector<int> v{1,3,37,1337,7};
+	
+	for(auto x : counted(v)){
+		std::cout << "v[" << x.index << "] = " << x.value << std::endl;
+	}
+	
+	for(auto x : counted(v)){
+		x.value *= x.index;
+	}
+	
+	for(auto x : counted(v)){
+		std::cout << "v[" << x.index << "] = " << x.value << std::endl;
+	}
+}
+
+void tuple_element (){
+	std::map<int, int> m1;
+	for(int i = -5; i <= 5; ++i)
+		m1[i] = i*i;
+	
+	for(auto & p : values(m1)){
+		p -= 5;
+	}
+	
+	auto const & m = m1;
+	for(auto & p : values(m)){		// p is a const ref
+		std::cout << p << "\t";
+	}
+	
+	std::cout << std::endl;
+	
+	for(auto & p : keys(m1)){		// p is a const ref, because keys in a map are const
+		std::cout << p << "\t";
+	}
+	
+	std::cout << std::endl;
+}
+		
+int main(){
+	counting_iterator();
+	tuple_element();
+}

ranges/tuple_element.hpp

@@ -0,0 +1,187 @@
+//
+//  main.cpp
+//  temp
+//
+//  Created by Joshua Moerman on 9/3/11.
+//  Copyright 2011 Vadovas. All rights reserved.
+//
+
+/*
+ Some helper function to easily iterate over a container of tuples. In
+ particular this is useful with maps. This is meant to be used in
+ range-based for loops.
+ 
+ Example:
+	map<string, int> m = {...};
+	for(auto & str : keys(m))
+		cout << str << "\t";
+	cout << endl;
+	for(auto & i : values(m))
+		cout << i << "\t";
+ 
+ keys() let you iterate over the keys of a map (the elements returned are
+ const references). values() let you iterate over the values.
+ There is a more general function for any container over tuples: nth_values.
+ 
+ Example:
+	vector<tuple<int, int, const int>> v = {...};
+	for(auto & i : nth_values<2>(v)){
+		cout << i << endl;
+		++i;		// error: attempting to write to read-only variable
+					// that's because i is a const ref.
+	}
+ 
+ That's all :). It's very trivial to just use i.first or get<0>(i),
+ but this might be very handy when debugging or something.
+ 
+ */
+
+#include <utility>
+
+namespace details {
+
+	/* lazy implementation, relies on inheritance
+	 only op* and op-> are overloaded (to return a specific element in
+	 the pair or tuple (note that std::get and std::tuple_element
+	 are overloaded for pair, to make pair look like a tuple :) ).
+	 */
+	template <size_t N, typename Iterator>
+	struct tuple_iterator : public Iterator {
+		tuple_iterator(Iterator it)
+		: Iterator(it)
+		{}
+		
+		typename std::tuple_element<N, typename Iterator::value_type>::type &
+		operator*(){
+			return std::get<N>(*(Iterator&)(*this));
+		}
+		
+		typename std::tuple_element<N, typename Iterator::value_type>::type &
+		operator->(){
+			return std::get<N>(*(Iterator&)(*this));
+		}
+	};
+
+	template <size_t N, typename Iterator>
+	struct const_tuple_iterator : public Iterator {
+		const_tuple_iterator(Iterator it)
+		: Iterator(it)
+		{}
+		
+		typename std::tuple_element<N, typename Iterator::value_type>::type const &
+		operator*(){
+			return std::get<N>(*(Iterator&)(*this));
+		}
+		
+		typename std::tuple_element<N, typename Iterator::value_type>::type const &
+		operator->(){
+			return std::get<N>(*(Iterator&)(*this));
+		}
+	};
+
+	/* The const_iterator is not really needed, since no-one will actually
+	 store a const tuple_container_wrapper, but it's here for completeness.
+	 */
+	template <size_t N, typename Container>
+	struct tuple_container_wrapper {
+		typedef tuple_iterator<N, typename Container::iterator> iterator;
+		typedef const_tuple_iterator<N, typename Container::const_iterator> const_iterator;
+		
+		tuple_container_wrapper(Container & c)
+		: c(c)
+		{}
+		
+		iterator begin(){
+			return iterator(c.begin());
+		}
+		
+		iterator end(){
+			return iterator(c.end());
+		}
+		
+		const_iterator begin() const {
+			return const_iterator(c.cbegin());
+		}
+		
+		const_iterator end() const {
+			return const_iterator(c.cend());
+		}
+		
+		const_iterator cbegin() const {
+			return const_iterator(c.cbegin());
+		}
+		
+		const_iterator cend() const {
+			return const_iterator(c.cend());
+		}
+		
+	private:
+		Container & c;
+	};
+	
+	template <size_t N, typename Container>
+	struct const_tuple_container_wrapper {
+		typedef const_tuple_iterator<N, typename Container::const_iterator> const_iterator;
+		
+		const_tuple_container_wrapper(Container const & c)
+		: c(c)
+		{}
+		
+		const_iterator begin() const {
+			return const_iterator(c.cbegin());
+		}
+		
+		const_iterator end() const {
+			return const_iterator(c.cend());
+		}
+		
+		const_iterator cbegin() const {
+			return const_iterator(c.cbegin());
+		}
+		
+		const_iterator cend() const {
+			return const_iterator(c.cend());
+		}
+		
+	private:
+		Container const & c;
+	};
+	
+}
+
+/* nth_values() is the general function to iterate over a specific
+ data element in the container (of tuples/pairs).
+ For map-types there are the functions keys() and values(), which are
+ special cases of this function.
+ */
+template <size_t N, typename Container>
+details::tuple_container_wrapper<N, Container>
+nth_values(Container & m) {
+	return details::tuple_container_wrapper<N, Container>(m);
+}
+
+template <size_t N, typename Container>
+details::const_tuple_container_wrapper<N, Container>
+nth_values(Container const & m) {
+	return details::const_tuple_container_wrapper<N, Container>(m);
+}
+
+// NOTE: keys in a map are always const, so a const-only function suffices
+template <typename Map>
+details::const_tuple_container_wrapper<0, Map>
+keys(Map const & m) {
+	return nth_values<0>(m);
+}
+
+template <typename Map>
+details::tuple_container_wrapper<1, Map>
+values(Map & m) {
+	return nth_values<1>(m);
+}
+
+template <typename Map>
+details::const_tuple_container_wrapper<1, Map>
+values(Map const & m) {
+	return nth_values<1>(m);
+}
+