A modern C++ metaprogramming library. It provides high level algorithms to manipulate heterogeneous sequences, allows writing type-level computations with a natural syntax, provides tools to introspect user-defined types and much more
Your standard library for metaprogramming
Overview
#include <boost/hana.hpp>
#include <cassert>
#include <string>
namespace hana = boost::hana;
using namespace hana::literals;
struct Fish { std::string name; };
struct Cat { std::string name; };
struct Dog { std::string name; };
int main() {
// Sequences capable of holding heterogeneous objects, and algorithms
// to manipulate them.
auto animals = hana::make_tuple(Fish{"Nemo"}, Cat{"Garfield"}, Dog{"Snoopy"});
auto names = hana::transform(animals, [](auto a) {
return a.name;
});
assert(hana::reverse(names) == hana::make_tuple("Snoopy", "Garfield", "Nemo"));
// No compile-time information is lost: even if `animals` can't be a
// constant expression because it contains strings, its length is constexpr.
static_assert(hana::length(animals) == 3u, "");
// Computations on types can be performed with the same syntax as that of
// normal C++. Believe it or not, everything is done at compile-time.
auto animal_types = hana::make_tuple(hana::type_c<Fish*>, hana::type_c<Cat&>, hana::type_c<Dog*>);
auto animal_ptrs = hana::filter(animal_types, [](auto a) {
return hana::traits::is_pointer(a);
});
static_assert(animal_ptrs == hana::make_tuple(hana::type_c<Fish*>, hana::type_c<Dog*>), "");
// And many other goodies to make your life easier, including:
// 1. Access to elements in a tuple with a sane syntax.
static_assert(animal_ptrs[0_c] == hana::type_c<Fish*>, "");
static_assert(animal_ptrs[1_c] == hana::type_c<Dog*>, "");
// 2. Unroll loops at compile-time without hassle.
std::string s;
hana::int_c<10>.times([&]{ s += "x"; });
// equivalent to s += "x"; s += "x"; ... s += "x";
// 3. Easily check whether an expression is valid.
// This is usually achieved with complex SFINAE-based tricks.
auto has_name = hana::is_valid([](auto&& x) -> decltype((void)x.name) { });
static_assert(has_name(animals[0_c]), "");
static_assert(!has_name(1), "");
}
Depends (5)
Builds
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_fedora_37-gcc_12.2-bindist |
timestamp |
2024-04-27 20:17:40 UTC (08:42:40 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-gcc_13-static_O3 |
timestamp |
2024-04-27 11:19:12 UTC (17:41:07 hours ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-gcc_13-ndebug_O3 |
timestamp |
2024-04-27 11:18:35 UTC (17:41:45 hours ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-gcc_13-O3 |
timestamp |
2024-04-27 11:17:20 UTC (17:43:00 hours ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-gcc_13 |
timestamp |
2024-04-27 11:15:15 UTC (17:45:05 hours ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_15_libc++ |
timestamp |
2024-04-27 09:41:10 UTC (19:19:10 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_15 |
timestamp |
2024-04-27 09:37:58 UTC (19:22:21 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_11-gcc_12 |
timestamp |
2024-04-27 09:22:47 UTC (19:37:32 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-gcc_12-bindist |
timestamp |
2024-04-27 08:27:09 UTC (20:33:10 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0_libc++-O3 |
timestamp |
2024-04-27 06:19:23 UTC (22:40:56 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0_libc++ |
timestamp |
2024-04-27 06:18:39 UTC (22:41:41 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0_libc++-static_O3 |
timestamp |
2024-04-27 06:16:49 UTC (22:43:30 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0-O3 |
timestamp |
2024-04-27 06:15:27 UTC (22:44:53 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0-static_O3 |
timestamp |
2024-04-27 06:14:15 UTC (22:46:05 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_16.0 |
timestamp |
2024-04-27 06:12:51 UTC (22:47:29 hours ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-clang_16.0_llvm_msvc_17.6 |
timestamp |
2024-04-27 04:14:45 UTC (01 00:45:35 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-clang_16.0_llvm_msvc_17.6-O2 |
timestamp |
2024-04-27 04:09:48 UTC (01 00:50:32 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-clang_16.0_llvm_msvc_17.6-static_O2 |
timestamp |
2024-04-27 04:09:25 UTC (01 00:50:55 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-msvc_17.6 |
timestamp |
2024-04-27 04:03:24 UTC (01 00:56:55 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-msvc_17.6-static_O2 |
timestamp |
2024-04-27 04:01:38 UTC (01 00:58:42 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-msvc_17.6-O2 |
timestamp |
2024-04-27 04:01:13 UTC (01 00:59:07 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-w64-mingw32 |
tgt config |
windows_10-gcc_12.2_mingw_w64-static_O2 |
timestamp |
2024-04-27 03:26:33 UTC (01 01:33:47 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-w64-mingw32 |
tgt config |
windows_10-gcc_12.2_mingw_w64-O2 |
timestamp |
2024-04-27 03:25:45 UTC (01 01:34:35 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-w64-mingw32 |
tgt config |
windows_10-gcc_12.2_mingw_w64 |
timestamp |
2024-04-27 03:21:00 UTC (01 01:39:20 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-msvc_17.5 |
timestamp |
2024-04-27 02:58:02 UTC (01 02:02:17 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-microsoft-win32-msvc14.3 |
tgt config |
windows_10-clang_15.0_msvc_msvc_17.6 |
timestamp |
2024-04-27 02:57:03 UTC (01 02:03:17 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-freebsd13.2 |
tgt config |
freebsd_13-clang_14.0-static_O3 |
timestamp |
2024-04-27 02:36:23 UTC (01 02:23:57 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-freebsd13.2 |
tgt config |
freebsd_13-clang_14.0-O3 |
timestamp |
2024-04-27 02:34:15 UTC (01 02:26:05 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-freebsd13.2 |
tgt config |
freebsd_13-clang_14.0 |
timestamp |
2024-04-27 02:33:41 UTC (01 02:26:38 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-freebsd12.4 |
tgt config |
freebsd_12-clang_13.0 |
timestamp |
2024-04-27 02:33:01 UTC (01 02:27:18 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_15.0 |
timestamp |
2024-04-27 02:30:05 UTC (01 02:30:15 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-clang_15.0_libc++ |
timestamp |
2024-04-27 02:23:36 UTC (01 02:36:44 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_11-gcc_12.1 |
timestamp |
2024-04-27 02:18:02 UTC (01 02:42:18 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_15.0-static_O3 |
timestamp |
2024-04-27 00:36:39 UTC (01 04:23:41 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_15.0-O3 |
timestamp |
2024-04-27 00:33:31 UTC (01 04:26:49 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_15.0 |
timestamp |
2024-04-27 00:30:43 UTC (01 04:29:37 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_14.0-static_O3 |
timestamp |
2024-04-26 15:24:41 UTC (01 13:35:38 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_14.0-O3 |
timestamp |
2024-04-26 15:24:04 UTC (01 13:36:16 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-clang_14.0 |
timestamp |
2024-04-26 15:23:24 UTC (01 13:36:56 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_fedora_38-gcc_13-bindist |
timestamp |
2024-04-26 12:23:26 UTC (01 16:36:53 days ago) |
result |
warning (update) | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-gcc_13.1-ndebug_O3 |
timestamp |
2024-04-26 12:09:36 UTC (01 16:50:44 days ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-gcc_13.1-static_O3 |
timestamp |
2024-04-26 12:06:21 UTC (01 16:53:58 days ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-gcc_13.1 |
timestamp |
2024-04-26 12:04:59 UTC (01 16:55:21 days ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
x86_64-linux-gnu |
tgt config |
linux_debian_12-gcc_13.1-O3 |
timestamp |
2024-04-26 12:04:58 UTC (01 16:55:22 days ago) |
result |
warning (update) | warning (test-installed) | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16_libc++-static_O3 |
timestamp |
2024-04-25 16:44:54 UTC (02 12:15:26 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16_libc++-O3 |
timestamp |
2024-04-25 16:42:01 UTC (02 12:18:19 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16_libc++ |
timestamp |
2024-04-25 16:41:44 UTC (02 12:18:36 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16-static_O3 |
timestamp |
2024-04-25 16:38:50 UTC (02 12:21:30 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16-O3 |
timestamp |
2024-04-25 16:38:35 UTC (02 12:21:45 days ago) |
result |
success | log | rebuild |
toolchain |
public-0.16.0 |
target |
aarch64-linux-gnu |
tgt config |
linux_debian_12-clang_16 |
timestamp |
2024-04-25 16:34:49 UTC (02 12:25:30 days ago) |
result |
success | log | rebuild |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-gcc_13_homebrew |
result |
excluded (https://github) |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-gcc_13_homebrew-O3 |
result |
excluded (https://github) |
target |
x86_64-apple-darwin22.5.0 |
tgt config |
macos_13-gcc_13_homebrew-static_O3 |
result |
excluded (https://github) |