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-rw-r--r--include/ftl/details/optional.h58
-rw-r--r--include/ftl/details/type_traits.h27
-rw-r--r--include/ftl/optional.h56
-rw-r--r--include/ftl/small_vector.h9
-rw-r--r--libs/ftl/optional_test.cpp59
5 files changed, 190 insertions, 19 deletions
diff --git a/include/ftl/details/optional.h b/include/ftl/details/optional.h
new file mode 100644
index 0000000000..bff7c1e000
--- /dev/null
+++ b/include/ftl/details/optional.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <functional>
+#include <optional>
+
+#include <ftl/details/type_traits.h>
+
+namespace android::ftl {
+
+template <typename>
+struct Optional;
+
+namespace details {
+
+template <typename>
+struct is_optional : std::false_type {};
+
+template <typename T>
+struct is_optional<std::optional<T>> : std::true_type {};
+
+template <typename T>
+struct is_optional<Optional<T>> : std::true_type {};
+
+template <typename F, typename T>
+struct transform_result {
+ using type = Optional<std::remove_cv_t<std::invoke_result_t<F, T>>>;
+};
+
+template <typename F, typename T>
+using transform_result_t = typename transform_result<F, T>::type;
+
+template <typename F, typename T>
+struct and_then_result {
+ using type = remove_cvref_t<std::invoke_result_t<F, T>>;
+ static_assert(is_optional<type>{}, "and_then function must return an optional");
+};
+
+template <typename F, typename T>
+using and_then_result_t = typename and_then_result<F, T>::type;
+
+} // namespace details
+} // namespace android::ftl
diff --git a/include/ftl/details/type_traits.h b/include/ftl/details/type_traits.h
new file mode 100644
index 0000000000..7092ec50fb
--- /dev/null
+++ b/include/ftl/details/type_traits.h
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <type_traits>
+
+namespace android::ftl::details {
+
+// TODO: Replace with std::remove_cvref_t in C++20.
+template <typename U>
+using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<U>>;
+
+} // namespace android::ftl::details
diff --git a/include/ftl/optional.h b/include/ftl/optional.h
index daf4502bd2..a0a95c4b9a 100644
--- a/include/ftl/optional.h
+++ b/include/ftl/optional.h
@@ -18,9 +18,10 @@
#include <functional>
#include <optional>
-#include <type_traits>
#include <utility>
+#include <ftl/details/optional.h>
+
namespace android::ftl {
// Superset of std::optional<T> with monadic operations, as proposed in https://wg21.link/P0798R8.
@@ -37,30 +38,59 @@ struct Optional final : std::optional<T> {
// Returns Optional<U> where F is a function that maps T to U.
template <typename F>
constexpr auto transform(F&& f) const& {
- using U = std::remove_cv_t<std::invoke_result_t<F, decltype(value())>>;
- if (has_value()) return Optional<U>(std::invoke(std::forward<F>(f), value()));
- return Optional<U>();
+ using R = details::transform_result_t<F, decltype(value())>;
+ if (has_value()) return R(std::invoke(std::forward<F>(f), value()));
+ return R();
}
template <typename F>
constexpr auto transform(F&& f) & {
- using U = std::remove_cv_t<std::invoke_result_t<F, decltype(value())>>;
- if (has_value()) return Optional<U>(std::invoke(std::forward<F>(f), value()));
- return Optional<U>();
+ using R = details::transform_result_t<F, decltype(value())>;
+ if (has_value()) return R(std::invoke(std::forward<F>(f), value()));
+ return R();
}
template <typename F>
constexpr auto transform(F&& f) const&& {
- using U = std::invoke_result_t<F, decltype(std::move(value()))>;
- if (has_value()) return Optional<U>(std::invoke(std::forward<F>(f), std::move(value())));
- return Optional<U>();
+ using R = details::transform_result_t<F, decltype(std::move(value()))>;
+ if (has_value()) return R(std::invoke(std::forward<F>(f), std::move(value())));
+ return R();
}
template <typename F>
constexpr auto transform(F&& f) && {
- using U = std::invoke_result_t<F, decltype(std::move(value()))>;
- if (has_value()) return Optional<U>(std::invoke(std::forward<F>(f), std::move(value())));
- return Optional<U>();
+ using R = details::transform_result_t<F, decltype(std::move(value()))>;
+ if (has_value()) return R(std::invoke(std::forward<F>(f), std::move(value())));
+ return R();
+ }
+
+ // Returns Optional<U> where F is a function that maps T to Optional<U>.
+ template <typename F>
+ constexpr auto and_then(F&& f) const& {
+ using R = details::and_then_result_t<F, decltype(value())>;
+ if (has_value()) return std::invoke(std::forward<F>(f), value());
+ return R();
+ }
+
+ template <typename F>
+ constexpr auto and_then(F&& f) & {
+ using R = details::and_then_result_t<F, decltype(value())>;
+ if (has_value()) return std::invoke(std::forward<F>(f), value());
+ return R();
+ }
+
+ template <typename F>
+ constexpr auto and_then(F&& f) const&& {
+ using R = details::and_then_result_t<F, decltype(std::move(value()))>;
+ if (has_value()) return std::invoke(std::forward<F>(f), std::move(value()));
+ return R();
+ }
+
+ template <typename F>
+ constexpr auto and_then(F&& f) && {
+ using R = details::and_then_result_t<F, decltype(std::move(value()))>;
+ if (has_value()) return std::invoke(std::forward<F>(f), std::move(value()));
+ return R();
}
};
diff --git a/include/ftl/small_vector.h b/include/ftl/small_vector.h
index 339726e4ea..11294c3ac8 100644
--- a/include/ftl/small_vector.h
+++ b/include/ftl/small_vector.h
@@ -21,11 +21,12 @@
#include <algorithm>
#include <iterator>
-#include <type_traits>
#include <utility>
#include <variant>
#include <vector>
+#include <ftl/details/type_traits.h>
+
namespace android::ftl {
template <typename>
@@ -80,10 +81,6 @@ class SmallVector final : details::ArrayTraits<T>, details::ArrayComparators<Sma
using Static = StaticVector<T, N>;
using Dynamic = SmallVector<T, 0>;
- // TODO: Replace with std::remove_cvref_t in C++20.
- template <typename U>
- using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<U>>;
-
public:
FTL_ARRAY_TRAIT(T, value_type);
FTL_ARRAY_TRAIT(T, size_type);
@@ -104,7 +101,7 @@ class SmallVector final : details::ArrayTraits<T>, details::ArrayComparators<Sma
// Constructs at most N elements. See StaticVector for underlying constructors.
template <typename Arg, typename... Args,
- typename = std::enable_if_t<!is_small_vector<remove_cvref_t<Arg>>{}>>
+ typename = std::enable_if_t<!is_small_vector<details::remove_cvref_t<Arg>>{}>>
SmallVector(Arg&& arg, Args&&... args)
: vector_(std::in_place_type<Static>, std::forward<Arg>(arg), std::forward<Args>(args)...) {}
diff --git a/libs/ftl/optional_test.cpp b/libs/ftl/optional_test.cpp
index ede159a955..ad8d3cf8ef 100644
--- a/libs/ftl/optional_test.cpp
+++ b/libs/ftl/optional_test.cpp
@@ -20,6 +20,7 @@
#include <ftl/unit.h>
#include <gtest/gtest.h>
+#include <cstdlib>
#include <functional>
#include <numeric>
#include <utility>
@@ -82,4 +83,62 @@ TEST(Optional, Transform) {
.transform([](const std::string& s) { return s.length(); }));
}
+namespace {
+
+Optional<int> parse_int(const std::string& str) {
+ if (const int i = std::atoi(str.c_str())) return i;
+ return std::nullopt;
+}
+
+} // namespace
+
+TEST(Optional, AndThen) {
+ // Empty.
+ EXPECT_EQ(std::nullopt, Optional<int>().and_then([](int) -> Optional<int> { return 0; }));
+ EXPECT_EQ(std::nullopt, Optional<int>().and_then([](int) { return Optional<int>(); }));
+
+ // By value.
+ EXPECT_EQ(0, Optional(0).and_then([](int x) { return Optional(x); }));
+ EXPECT_EQ(123, Optional("123").and_then(parse_int));
+ EXPECT_EQ(std::nullopt, Optional("abc").and_then(parse_int));
+
+ // By reference.
+ {
+ Optional opt = 'x';
+ EXPECT_EQ('z', opt.and_then([](char& c) {
+ c = 'y';
+ return Optional('z');
+ }));
+
+ EXPECT_EQ('y', opt);
+ }
+
+ // By rvalue reference.
+ {
+ std::string out;
+ EXPECT_EQ("xyz"s, Optional("abc"s).and_then([&out](std::string&& str) {
+ out = std::move(str);
+ return Optional("xyz"s);
+ }));
+
+ EXPECT_EQ(out, "abc"s);
+ }
+
+ // Chaining.
+ using StringVector = StaticVector<std::string, 3>;
+ EXPECT_EQ(14u, Optional(StaticVector{"-"s, "1"s})
+ .and_then([](StringVector&& v) -> Optional<StringVector> {
+ if (v.push_back("4"s)) return v;
+ return {};
+ })
+ .and_then([](const StringVector& v) -> Optional<std::string> {
+ if (v.full()) return std::accumulate(v.begin(), v.end(), std::string());
+ return {};
+ })
+ .and_then(parse_int)
+ .and_then([](int i) {
+ return i > 0 ? std::nullopt : std::make_optional(static_cast<unsigned>(-i));
+ }));
+}
+
} // namespace android::test
generated by cgit v1.2.3-59-g8ed1b (git 2.39.0) at 2025-10-20 00:11:07 +0000