FTL: Add Optional<T>::and_then
Bug: 185536303
Test: ftl_test
Change-Id: Ic907a662a2090ad1363bd329e7d758b2acef55ad
diff --git a/libs/ftl/optional_test.cpp b/libs/ftl/optional_test.cpp
index ede159a..ad8d3cf 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 @@
.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