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/*
# utility
Lots of miscelaneous utilities.
http://en.cppreference.com/w/cpp/utility
*/
#include "common.hpp"
int main() {
#if __cplusplus >= 201103L
/*
# tuple
Hold a ordered collection of elements.
Each element can be of a different type.
The length is always fixed.
*/
{
//create
{
//constructor
{
std::tuple<int,char,std::string> t0(0, 'a', "a");
}
/*
# make_tuple
forwards arguments to tuple constructor.
The advantage over the constructor is that since it is a function
template argument deduction can be done, so we don't need to type in
template arguments.
Remember that template argument deduction cannot be done for constructors.
*/
{
std::tuple<int,char,std::string> t;
//without make_tuple
t = std::make_tuple(0, 'a', "a");
t = std::tuple<int,char,std::string>(0, 'a', "a");
//with make_tuple
}
//tuple from pair
{
std::tuple<int,char> t2( std::pair<int,char>(0, 'a'));
}
//uniform initialization
{
std::tuple<int,char,std::string> t{0, 'a', "a"};
}
// Fails because the tuple constructor are is `explicit`!
// TODO Rationale? <http://stackoverflow.com/questions/14961809/returning-a-tuple-from-a-function-using-uniform-initialization-syntax>
{
//std::tuple<int, int> t = {0, 1};
//std::tuple<int, int> t[]{{0, 1}};
}
}
/*
# get
Get single element from tuple.
Returns references, so it is possible to modify the tuples with them.
Copies are made from input elements
*/
{
std::tuple<int,std::string> t0(0, "abc");
assert(std::get<0>(t0) == 0);
assert(std::get<1>(t0) == "abc");
std::get<0>(t0) = 1;
assert(std::get<0>(t0) == 1);
std::get<1>(t0)[0] = '0';
assert(std::get<1>(t0) == "0bc");
}
/*
# tie
Unpack a tuple.
Unpack by reference seems not to be possible: <http://stackoverflow.com/questions/16571883/unpacking-a-std-tuple-into-pointers>
# ignore
Magic that exists only to ignore one of tie outputs.
*/
{
int i;
std::string s;
std::tuple<int,float,std::string> t(1, 1.5, "abc");
std::tie(i, std::ignore, s) = t;
assert(i == 1);
assert(s == "abc");
// Clearly copies are made.
i = 2;
assert(std::get<0>(t) == 1);
}
/*
Relational operators operations are implemented
<http://www.cplusplus.com/reference/tuple/tuple/operators/>
`<` family is lexicographical.
*/
{
std::tuple<int,char> t0(0, 'a');
std::tuple<int,char> t1(0, 'a');
std::tuple<int,char> t2(1, 'b');
std::tuple<int,char> t3(-1, 'b');
std::tuple<int,char> t4(0, 'b');
assert(t0 == t1);
assert(t0 != t2);
assert(t0 < t2);
assert(t0 > t3); //-1 counts
assert(t0 < t4); //0 ties, 'a' < 'b'
}
//swap contents of two tuples of same type
{
std::tuple<int,char> t0(0, 'a');
std::tuple<int,char> t1(1, 'b');
std::tuple<int,char> old_t0 = t0;
std::tuple<int,char> old_t1 = t1;
t0.swap(t1);
assert(t0 == old_t1);
assert(t1 == old_t0);
}
}
#endif
/*
# pair
Particular case of tuple for two elements
Methods which also exist for tuple will not be discussed.
Specially important because of `map`.
*/
{
//access: can also be done via `.first` and `.second` in addition to tuple `get`.
{
std::pair<int,char> p(0, 'a');
assert(std::get<0>(p) == p.first);
assert(std::get<1>(p) == p.second);
}
}
/*
# forward
TODO
*/
{
}
}