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//
// 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);
}