From 40588e30f6ab1d200180ba03e7e0823d20b642bc Mon Sep 17 00:00:00 2001
From: Tobias Zindl <zie.develop@gmail.com>
Date: Thu, 5 Oct 2023 22:27:16 +0200
Subject: [PATCH] :sparkles: add integral constant

---
 include/zll/meta/integral_constant.hpp        | 27 +++++++++++++++
 tests/unit_tests/meson.build                  |  2 +-
 .../meta/integral_constant_tests.cpp          | 33 +++++++++++++++++++
 3 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 include/zll/meta/integral_constant.hpp
 create mode 100644 tests/unit_tests/meta/integral_constant_tests.cpp

diff --git a/include/zll/meta/integral_constant.hpp b/include/zll/meta/integral_constant.hpp
new file mode 100644
index 0000000..3cb3f32
--- /dev/null
+++ b/include/zll/meta/integral_constant.hpp
@@ -0,0 +1,27 @@
+#ifndef ZLL_META_INTEGRALCONSTANT_HPP
+#define ZLL_META_INTEGRALCONSTANT_HPP
+
+namespace zll {
+namespace meta {
+
+template <typename T, T VALUE_V>
+struct integral_constant {
+    typedef T value_type;
+    typedef integral_constant<T, VALUE_V> type;
+
+    static const value_type value = VALUE_V;
+
+    operator value_type() const { return VALUE_V; }
+    value_type operator()() const { return VALUE_V; }
+};
+
+template <bool BOOL_V>
+struct bool_constant : integral_constant<bool, BOOL_V> {};
+
+typedef bool_constant<true> true_type;
+typedef bool_constant<false> false_type;
+
+}  // namespace meta
+}  // namespace zll
+
+#endif  // ZLL_META_INTEGRALCONSTANT_HPP
diff --git a/tests/unit_tests/meson.build b/tests/unit_tests/meson.build
index cec2190..cf821f8 100644
--- a/tests/unit_tests/meson.build
+++ b/tests/unit_tests/meson.build
@@ -1,5 +1,6 @@
 
 unit_tests_srcs = [
+    'meta/integral_constant_tests.cpp',
     'main.cpp',
 ]
 
@@ -9,7 +10,6 @@ unit_tests_exec = executable(
     unit_tests_srcs,
     include_directories: unit_tests_inc_dir,
     dependencies: [utest_dep, dis_dep],
-    override_options: ['cpp_std=c++20', 'warning_level=3'],
 )
 
 test('zll-unit-tests', unit_tests_exec, suite: 'dis')
diff --git a/tests/unit_tests/meta/integral_constant_tests.cpp b/tests/unit_tests/meta/integral_constant_tests.cpp
new file mode 100644
index 0000000..abd0449
--- /dev/null
+++ b/tests/unit_tests/meta/integral_constant_tests.cpp
@@ -0,0 +1,33 @@
+#include "zll/meta/integral_constant.hpp"
+#include "zll/debug/static_assert.hpp"
+
+#include <utest.h>
+
+UTEST(meta_integral_constant, int_constant) {
+    typedef zll::meta::integral_constant<int, 2> two_t;
+
+    const two_t two = two_t();
+    ASSERT_EQ(two_t::value, 2);
+    ASSERT_EQ(two(), 2);
+    const int val = two;
+
+    ASSERT_EQ(val, 2);
+    ZLL_STATIC_ASSERT((two_t::value == 2));
+}
+
+UTEST(meta_integral_constant, bool_constant) {
+    {
+        const zll::meta::true_type true_v;
+        ASSERT_TRUE((zll::meta::true_type::value));
+        ASSERT_TRUE(true_v);
+        ASSERT_TRUE(true_v());
+        ZLL_STATIC_ASSERT((zll::meta::true_type::value));
+    }
+    {
+        const zll::meta::false_type false_v;
+        ASSERT_FALSE((zll::meta::false_type::value));
+        ASSERT_FALSE(false_v);
+        ASSERT_FALSE(false_v());
+        ZLL_STATIC_ASSERT(!(zll::meta::false_type::value));
+    }
+}