feat: add cmp to iterator interface (#114)

* feat: add cmp to iterator interface

* fix: compilation error with std::expected

Author: uncommon-nickname

include/rusty_iterators/interface.hpp

@@ -61,6 +61,13 @@ using iterator::Take;
 using iterator::Zip;
 using iterator::ZipLongest;
 
+enum class Ordering : uint8_t
+{
+    Equal,
+    Less,
+    Greater,
+};
+
 template <class T, class Derived>
 class IterInterface
 {
@@ -85,6 +92,9 @@ class IterInterface
         requires AllFunctor<T, Functor>
     [[nodiscard]] auto all(Functor&& f) -> bool;
 
+    template <class Other>
+    [[nodiscard]] auto cmp(Other&& it) -> Ordering;
+
     [[nodiscard]] auto collect() -> std::vector<T>;
     [[nodiscard]] auto count() -> size_t;
 
@@ -229,7 +239,7 @@ template <class Functor>
     requires rusty_iterators::concepts::AnyFunctor<T, Functor>
 auto rusty_iterators::interface::IterInterface<T, Derived>::any(Functor&& f) -> bool // NOLINT
 {
-    auto anyf = [f = std::forward<Functor>(f)](auto acc, auto x) {
+    auto anyf = [f = std::forward<Functor>(f)](auto acc, auto x) -> std::expected<bool, bool> {
         return f(x) ? std::expected<bool, bool>{true} : std::unexpected{false};
     };
     return self().tryFold(false, std::move(anyf));
@@ -240,12 +250,31 @@ template <class Functor>
     requires rusty_iterators::concepts::AllFunctor<T, Functor>
 auto rusty_iterators::interface::IterInterface<T, Derived>::all(Functor&& f) -> bool // NOLINT
 {
-    auto allf = [f = std::forward<Functor>(f)](auto acc, auto x) {
+    auto allf = [f = std::forward<Functor>(f)](auto acc, auto x) -> std::expected<bool, bool> {
         return !f(x) ? std::expected<bool, bool>{false} : std::unexpected{true};
     };
     return self().tryFold(true, std::move(allf));
 }
 
+template <class T, class Derived>
+template <class Other>
+auto rusty_iterators::interface::IterInterface<T, Derived>::cmp(Other&& it) -> Ordering
+{
+    auto func = [](auto acc, auto x) -> std::expected<Ordering, Ordering> {
+        auto left  = std::get<0>(x);
+        auto right = std::get<1>(x);
+
+        if (left > right)
+            return std::expected<Ordering, Ordering>{Ordering::Greater};
+
+        if (left < right)
+            return std::expected<Ordering, Ordering>{Ordering::Less};
+
+        return std::unexpected{Ordering::Equal};
+    };
+    return self().zipLongest(std::forward<Other>(it)).tryFold(Ordering::Equal, std::move(func));
+}
+
 template <class T, class Derived>
 auto rusty_iterators::interface::IterInterface<T, Derived>::collect() -> std::vector<T>
 {

tests/iterator.test.cpp

@@ -3,6 +3,7 @@
 
 #include <rusty_iterators/iterator.hpp>
 
+using ::rusty_iterators::interface::Ordering;
 using ::rusty_iterators::iterator::LazyIterator;
 using ::testing::ElementsAreArray;
 
@@ -411,3 +412,53 @@ TEST(TestIterator, TestGetWithUbAndLb)
 
     EXPECT_THAT(it.collect(), ElementsAreArray({2, 3}));
 }
+
+TEST(TestIterator, TestCmpLongerVector)
+{
+    auto v1 = std::vector{1, 2, 3};
+    auto v2 = std::vector{1, 2};
+
+    auto result = LazyIterator{v1}.cmp(LazyIterator{v2});
+
+    ASSERT_EQ(result, Ordering::Greater);
+}
+
+TEST(TestIterator, TestCmpShorterVector)
+{
+    auto v1 = std::vector{1, 2};
+    auto v2 = std::vector{1, 2, 3};
+
+    auto result = LazyIterator{v1}.cmp(LazyIterator{v2});
+
+    ASSERT_EQ(result, Ordering::Less);
+}
+
+TEST(TestIterator, TestCmpEqualVectors)
+{
+    auto v1 = std::vector{1, 2, 3};
+    auto v2 = std::vector{1, 2, 3};
+
+    auto result = LazyIterator{v1}.cmp(LazyIterator{v2});
+
+    ASSERT_EQ(result, Ordering::Equal);
+}
+
+TEST(TestIterator, TestCmpGreaterValue)
+{
+    auto v1 = std::vector{1, 2, 3};
+    auto v2 = std::vector{1, 2, 4};
+
+    auto result = LazyIterator{v1}.cmp(LazyIterator{v2});
+
+    ASSERT_EQ(result, Ordering::Less);
+}
+
+TEST(TestIterator, TestCmpShorterValue)
+{
+    auto v1 = std::vector{1, 2, 3};
+    auto v2 = std::vector{1, 2, 2};
+
+    auto result = LazyIterator{v1}.cmp(LazyIterator{v2});
+
+    ASSERT_EQ(result, Ordering::Greater);
+}