Add option::transform and option::or_else

asl/option.hpp

@@ -429,6 +429,53 @@ public:
         }
         return un_cvref_t<result_of_t<F(T)>>{};
     }
+
+    template<typename F>
+    constexpr auto transform(F&& f) &
+    {
+        using U = un_cvref_t<result_of_t<F(T&)>>;
+        if (has_value())
+        {
+            return option<U>{ invoke(ASL_FWD(f), value()) };
+        }
+        return option<U>{};
+    }
+
+    template<typename F>
+    constexpr auto transform(F&& f) const&
+    {
+        using U = un_cvref_t<result_of_t<F(const T&)>>;
+        if (has_value())
+        {
+            return option<U>{ invoke(ASL_FWD(f), value()) };
+        }
+        return option<U>{};
+    }
+
+    template<typename F>
+    constexpr auto transform(F&& f) &&
+    {
+        using U = un_cvref_t<result_of_t<F(T)>>;
+        if (has_value())
+        {
+            return option<U>{ invoke(ASL_FWD(f), ASL_MOVE(value())) };
+        }
+        return option<U>{};
+    }
+
+    template<typename F>
+    constexpr option or_else(F&& f) const&
+        requires is_same<un_cvref_t<result_of_t<F()>>, option>
+    {
+        return has_value() ? *this : invoke(ASL_FWD(f));
+    }
+
+    template<typename F>
+    constexpr option or_else(F&& f) &&
+        requires is_same<un_cvref_t<result_of_t<F()>>, option>
+    {
+        return has_value() ? ASL_MOVE(*this) : invoke(ASL_FWD(f));
+    }
 };
 
 template<typename T>

asl/tests/option_tests.cpp

@@ -241,3 +241,38 @@ ASL_TEST(and_then)
     static_assert(asl::is_same<decltype(b2), asl::option<float>>);
     ASL_TEST_ASSERT(!b2.has_value());
 }
+
+ASL_TEST(transform)
+{
+    asl::option<int> a = 5;
+    asl::option<int> b;
+
+    auto fn = [](int x) -> float { return static_cast<float>(x) + 0.5F; };
+
+    auto a2 = a.transform(fn);
+    static_assert(asl::is_same<decltype(a2), asl::option<float>>);
+    ASL_TEST_ASSERT(a2.has_value());
+    ASL_TEST_EXPECT(a2.value() == 5.5F);
+
+    auto b2 = b.transform(fn);
+    static_assert(asl::is_same<decltype(b2), asl::option<float>>);
+    ASL_TEST_ASSERT(!b2.has_value());
+}
+
+ASL_TEST(or_else)
+{
+    asl::option<int> a = 5;
+    asl::option<int> b;
+
+    auto fn = []() -> asl::option<int> { return 12; };
+
+    auto a2 = a.or_else(fn);
+    static_assert(asl::is_same<decltype(a2), asl::option<int>>);
+    ASL_TEST_ASSERT(a2.has_value());
+    ASL_TEST_EXPECT(a2.value() == 5);
+
+    auto b2 = b.or_else(fn);
+    static_assert(asl::is_same<decltype(b2), asl::option<int>>);
+    ASL_TEST_ASSERT(b2.has_value());
+    ASL_TEST_EXPECT(b2.value() == 12);
+}