Metal

Metal is a single-header C++11 library designed to make you love template metaprogramming.

Overview

#include <metal.hpp>

// First we need some Values
union x { char payload[10]; };
class y { public: char c; };
struct z { char c; int i; };

// ... from which we construct some Lists
using l0 = metal::list<>;
using l1 = metal::prepend<l0, x>;
using l2 = metal::append<l1, z>;
using l3 = metal::insert<l2, metal::number<1>, y>;

static_assert(metal::same<l1, metal::list<x>>::value, "");
static_assert(metal::same<l2, metal::list<x, z>>::value, "");
static_assert(metal::same<l3, metal::list<x, y, z>>::value, "");

// Lists are versatile, we can check their sizes...
static_assert(metal::size<l0>::value == 0, "");
static_assert(metal::size<l1>::value == 1, "");
static_assert(metal::size<l2>::value == 2, "");
static_assert(metal::size<l3>::value == 3, "");

// retrieve their elements...
static_assert(metal::same<metal::front<l3>, x>::value, "");
static_assert(metal::same<metal::back<l3>, z>::value, "");
static_assert(metal::same<metal::at<l3, metal::number<1>>, y>::value, "");

// count those that satisfy a predicate...
static_assert(metal::count_if<l3, metal::trait<std::is_class>>::value == 2, "");
static_assert(metal::count_if<l3, metal::trait<std::is_union>>::value == 1, "");

// We can create new Lists by removing elements...
using l0_ = metal::drop<l3, metal::number<3>>;
using l1_ = metal::take<l3, metal::number<1>>;
using l2_ = metal::erase<l3, metal::number<1>>;

static_assert(metal::same<l0, l0_>::value, "");
static_assert(metal::same<l1, l1_>::value, "");
static_assert(metal::same<l2, l2_>::value, "");

// by reversing the order of elements...
static_assert(metal::same<metal::reverse<l0>, metal::list<>>::value, "");
static_assert(metal::same<metal::reverse<l1>, metal::list<x>>::value, "");
static_assert(metal::same<metal::reverse<l2>, metal::list<z, x>>::value, "");
static_assert(metal::same<metal::reverse<l3>, metal::list<z, y, x>>::value, "");

// by transforming the elements...
using l2ptrs = metal::transform<metal::lazy<std::add_pointer>, l2>;
using l3refs = metal::transform<metal::lazy<std::add_lvalue_reference>, l3>;

static_assert(metal::same<l2ptrs, metal::list<x*, z*>>::value, "");
static_assert(metal::same<l3refs, metal::list<x&, y&, z&>>::value, "");

// even by sorting them...
template<class x, class y>
using smaller = metal::number<(sizeof(x) < sizeof(y))>;

using sorted = metal::sort<l3, metal::lambda<smaller>>;

static_assert(metal::same<sorted, metal::list<y, z, x>>::value, "");

// that and much more!

Quick Start

1. Download metal.hpp
2. #include </path/to/metal.hpp>
3. Love template metaprogramming

Blazingly Fast

You don't need to just take my word for it, see for yourself at metaben.ch.

Portable

Metal is known to work on GCC, Clang, Visual Studio, and Xcode.

Documentation

The complete up-to-date documentation is available online.

License

This project is licensed under the MIT.