Add option::and_then

2 files changed, 59 insertions, 9 deletions

diff --git a/asl/option.hpp b/asl/option.hpp
index ab88992..ebb9eef 100644
--- a/asl/option.hpp
+++ b/asl/option.hpp
@@ -3,6 +3,7 @@
 #include "asl/assert.hpp"

 #include "asl/meta.hpp"

 #include "asl/maybe_uninit.hpp"

+#include "asl/functional.hpp"

 

 namespace asl

 {

@@ -334,7 +335,6 @@ public:
 

     constexpr bool has_value() const { return m_has_value; }

 

-    // @Todo Do we want this on rvalues? Or maybe some kind of unwrap?

     constexpr T&& value() &&

     {

         ASL_ASSERT(m_has_value); // @Todo Release assert

@@ -389,13 +389,46 @@ public:
     }

 

     template<typename... Args>

-    T& emplace(Args&&... args) &

+    constexpr T& emplace(Args&&... args) &

         requires constructible<T, Args&&...>

     {

         if (m_has_value) { reset(); }

         construct(ASL_FWD(args)...);

         return value();

     }

+

+    template<typename F>

+    constexpr auto and_then(F&& f) &

+        requires is_option<result_of_t<F(T&)>>

+    {

+        if (has_value())

+        {

+            return invoke(ASL_FWD(f), value());

+        }

+        return un_cvref_t<result_of_t<F(T&)>>{};

+    }

+

+    template<typename F>

+    constexpr auto and_then(F&& f) const&

+        requires is_option<result_of_t<F(const T&)>>

+    {

+        if (has_value())

+        {

+            return invoke(ASL_FWD(f), value());

+        }

+        return un_cvref_t<result_of_t<F(const T&)>>{};

+    }

+

+    template<typename F>

+    constexpr auto and_then(F&& f) &&

+        requires is_option<result_of_t<F(T)>>

+    {

+        if (has_value())

+        {

+            return invoke(ASL_FWD(f), ASL_MOVE(value()));

+        }

+        return un_cvref_t<result_of_t<F(T)>>{};

+    }

 };

 

 template<typename T>

diff --git a/asl/tests/option_tests.cpp b/asl/tests/option_tests.cpp
index 73998f8..ea20b98 100644
--- a/asl/tests/option_tests.cpp
+++ b/asl/tests/option_tests.cpp
@@ -155,18 +155,18 @@ ASL_TEST(convert_copy)
     asl::option<uint8_t> opt8 = uint8_t{8};

     asl::option<uint16_t> opt16 = opt8;

     

-    ASL_TEST_EXPECT(opt16.has_value());

+    ASL_TEST_ASSERT(opt16.has_value());

     ASL_TEST_EXPECT(opt16.value() == 8);

 

     opt8 = uint8_t{10};

-    ASL_TEST_EXPECT(opt8.has_value());

+    ASL_TEST_ASSERT(opt8.has_value());

     ASL_TEST_EXPECT(opt8.value() == 10);

     

     opt16 = asl::nullopt;

     ASL_TEST_EXPECT(!opt16.has_value());

     

     opt16 = opt8;

-    ASL_TEST_EXPECT(opt16.has_value());

+    ASL_TEST_ASSERT(opt16.has_value());

     ASL_TEST_EXPECT(opt16.value() == 10);

 }

 

@@ -175,18 +175,18 @@ ASL_TEST(convert_move)
     asl::option<uint8_t> opt8 = uint8_t{8};

     asl::option<uint16_t> opt16 = ASL_MOVE(opt8);

     

-    ASL_TEST_EXPECT(opt16.has_value());

+    ASL_TEST_ASSERT(opt16.has_value());

     ASL_TEST_EXPECT(opt16.value() == 8);

 

     opt8 = ASL_MOVE(uint8_t{10});

-    ASL_TEST_EXPECT(opt8.has_value());

+    ASL_TEST_ASSERT(opt8.has_value());

     ASL_TEST_EXPECT(opt8.value() == 10);

     

     opt16 = asl::nullopt;

     ASL_TEST_EXPECT(!opt16.has_value());

     

     opt16 = ASL_MOVE(opt8);

-    ASL_TEST_EXPECT(opt16.has_value());

+    ASL_TEST_ASSERT(opt16.has_value());

     ASL_TEST_EXPECT(opt16.value() == 10);

 }

 

@@ -204,7 +204,7 @@ ASL_TEST(emplace)
     asl::option<int> a = asl::nullopt;

 

     a.emplace(42);

-    ASL_TEST_EXPECT(a.has_value());

+    ASL_TEST_ASSERT(a.has_value());

     ASL_TEST_EXPECT(a.value() == 42);

 }

 

@@ -224,3 +224,20 @@ ASL_TEST(emplace_destroys_previous)
     

     ASL_TEST_EXPECT(b2);

 }

+

+ASL_TEST(and_then)

+{

+    asl::option<int> a = 5;

+    asl::option<int> b;

+

+    auto fn = [](int x) -> asl::option<float> { return static_cast<float>(x) + 0.5F; };

+

+    auto a2 = a.and_then(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.and_then(fn);

+    static_assert(asl::is_same<decltype(b2), asl::option<float>>);

+    ASL_TEST_ASSERT(!b2.has_value());

+}