kstd/vector: implement single-element erase

2 files changed, 107 insertions, 0 deletions

diff --git a/libs/kstd/include/kstd/vector b/libs/kstd/include/kstd/vector
index 0d4aac8..74aefa9 100644
--- a/libs/kstd/include/kstd/vector
+++ b/libs/kstd/include/kstd/vector
@@ -690,6 +690,22 @@ namespace kstd
       return begin() + prefix_size;
     }
 
+    constexpr auto erase(const_iterator position) -> iterator
+    {
+      if (position == end())
+      {
+        os::panic("[kstd:vector] Attempted to erase end()!");
+      }
+
+      auto prefix_size = std::ranges::distance(cbegin(), position);
+
+      std::ranges::move(begin() + prefix_size + 1, end(), begin() + prefix_size);
+      std::allocator_traits<allocator_type>::destroy(m_allocator, end() - 1);
+      --m_size;
+
+      return begin() + prefix_size;
+    }
+
     //! Append a given element to this vector via copy construction.
     constexpr auto push_back(value_type const & value) -> void
     {
diff --git a/libs/kstd/tests/src/vector.cpp b/libs/kstd/tests/src/vector.cpp
index 0735c9a..3ff041f 100644
--- a/libs/kstd/tests/src/vector.cpp
+++ b/libs/kstd/tests/src/vector.cpp
@@ -649,6 +649,45 @@ SCENARIO("Vector modifiers", "[vector]")
         REQUIRE(it == v.begin() + 1);
       }
     }
+
+    WHEN("erasing the first element")
+    {
+      auto it = v.erase(v.cbegin());
+
+      THEN("the first element is removed and the size decreases")
+      {
+        REQUIRE(v.size() == 2);
+        REQUIRE(v[0] == 20);
+        REQUIRE(v[1] == 30);
+        REQUIRE(it == v.begin());
+      }
+    }
+
+    WHEN("erasing a middle element")
+    {
+      auto it = v.erase(v.cbegin() + 1);
+
+      THEN("the middle element is removed and the size decreases")
+      {
+        REQUIRE(v.size() == 2);
+        REQUIRE(v[0] == 10);
+        REQUIRE(v[1] == 30);
+        REQUIRE(it == v.begin() + 1);
+      }
+    }
+
+    WHEN("erasing the last element")
+    {
+      auto it = v.erase(v.cend() - 1);
+
+      THEN("the last element is removed and the size decreases")
+      {
+        REQUIRE(v.size() == 2);
+        REQUIRE(v[0] == 10);
+        REQUIRE(v[1] == 20);
+        REQUIRE(it == v.end());
+      }
+    }
   }
 }
 
@@ -868,6 +907,58 @@ SCENARIO("Vector modifier move semantics", "[vector]")
         REQUIRE(v[3].was_moved);
       }
     }
+
+    WHEN("erasing an element in the middle")
+    {
+      for (auto& elem : v)
+      {
+        elem.was_copied = false;
+        elem.was_moved = false;
+      }
+
+      auto it = v.erase(v.cbegin() + 1);
+
+      THEN("the subsequent elements are move-assigned leftwards")
+      {
+        REQUIRE(v.size() == 2);
+        
+        REQUIRE(v[0].value == 10);
+        REQUIRE_FALSE(v[0].was_moved);
+        REQUIRE_FALSE(v[0].was_copied);
+
+        REQUIRE(v[1].value == 30);
+        REQUIRE(v[1].was_moved);
+        REQUIRE_FALSE(v[1].was_copied);
+
+        REQUIRE(it == v.begin() + 1);
+      }
+    }
+
+    WHEN("erasing the last element")
+    {
+      for (auto& elem : v)
+      {
+        elem.was_copied = false;
+        elem.was_moved = false;
+      }
+
+      auto it = v.erase(v.cend() - 1);
+
+      THEN("no elements are moved, just the last element destroyed")
+      {
+        REQUIRE(v.size() == 2);
+
+        REQUIRE(v[0].value == 10);
+        REQUIRE_FALSE(v[0].was_moved);
+        REQUIRE_FALSE(v[0].was_copied);
+
+        REQUIRE(v[1].value == 20);
+        REQUIRE_FALSE(v[1].was_moved);
+        REQUIRE_FALSE(v[1].was_copied);
+
+        REQUIRE(it == v.end());
+      }
+    }
   }
 }