BLI: Return number of values removed from remove_if

Make the `remove_if` function for `Vector`, `VectorSet`, `Set`, and `Map` return the number of elements it removed.

Pull Request: https://projects.blender.org/blender/blender/pulls/107069

source/blender/blenlib/BLI_map.hh

@@ -885,12 +885,14 @@ class Map {
   }
 
   /**
-   * Remove all key-value-pairs for that the given predicate is true.
+   * Remove all key-value-pairs for that the given predicate is true and return the number of
+   * removed pairs.
    *
    * This is similar to std::erase_if.
    */
-  template<typename Predicate> void remove_if(Predicate &&predicate)
+  template<typename Predicate> int64_t remove_if(Predicate &&predicate)
   {
+    const int64_t prev_size = this->size();
     for (Slot &slot : slots_) {
       if (slot.is_occupied()) {
         const Key &key = *slot.key();
@@ -901,6 +903,7 @@ class Map {
         }
       }
     }
+    return prev_size - this->size();
   }
 
   /**

source/blender/blenlib/BLI_set.hh

@@ -489,12 +489,14 @@ class Set {
   }
 
   /**
-   * Remove all values for which the given predicate is true.
+   * Remove all values for which the given predicate is true and return the number of removed
+   * values.
    *
    * This is similar to std::erase_if.
    */
-  template<typename Predicate> void remove_if(Predicate &&predicate)
+  template<typename Predicate> int64_t remove_if(Predicate &&predicate)
   {
+    const int64_t prev_size = this->size();
     for (Slot &slot : slots_) {
       if (slot.is_occupied()) {
         const Key &key = *slot.key();
@@ -504,6 +506,7 @@ class Set {
         }
       }
     }
+    return prev_size - this->size();
   }
 
   /**

source/blender/blenlib/BLI_vector.hh

@@ -816,14 +816,17 @@ class Vector {
   }
 
   /**
-   * Remove all values for which the given predicate is true.
+   * Remove all values for which the given predicate is true and return the number of values
+   * removed.
    *
    * This is similar to std::erase_if.
    */
-  template<typename Predicate> void remove_if(Predicate &&predicate)
+  template<typename Predicate> int64_t remove_if(Predicate &&predicate)
   {
+    const T *prev_end = this->end();
     end_ = std::remove_if(this->begin(), this->end(), predicate);
     UPDATE_VECTOR_SIZE(this);
+    return int64_t(prev_end - end_);
   }
 
   /**

source/blender/blenlib/BLI_vector_set.hh

@@ -347,13 +347,14 @@ class VectorSet {
   }
 
   /**
-   * Remove all values for which the given predicate is true. This may change the order of elements
-   * in the vector.
+   * Remove all values for which the given predicate is true and return the number or values
+   * removed. This may change the order of elements in the vector.
    *
    * This is similar to std::erase_if.
    */
-  template<typename Predicate> void remove_if(Predicate &&predicate)
+  template<typename Predicate> int64_t remove_if(Predicate &&predicate)
   {
+    const int64_t prev_size = this->size();
     for (Slot &slot : slots_) {
       if (slot.is_occupied()) {
         const int64_t index = slot.index();
@@ -363,6 +364,7 @@ class VectorSet {
         }
       }
     }
+    return prev_size - this->size();
   }
 
   /**

source/blender/blenlib/tests/BLI_map_test.cc

@@ -646,8 +646,8 @@ TEST(map, RemoveIf)
   for (const int64_t i : IndexRange(100)) {
     map.add(i * i, i);
   }
-  map.remove_if([](auto item) { return item.key > 100; });
-  EXPECT_EQ(map.size(), 11);
+  const int64_t removed = map.remove_if([](auto item) { return item.key > 100; });
+  EXPECT_EQ(map.size() + removed, 100);
   for (const int64_t i : IndexRange(100)) {
     if (i <= 10) {
       EXPECT_EQ(map.lookup(i * i), i);

source/blender/blenlib/tests/BLI_set_test.cc

@@ -582,8 +582,8 @@ TEST(set, RemoveIf)
   for (const int64_t i : IndexRange(100)) {
     set.add(i * i);
   }
-  set.remove_if([](const int64_t key) { return key > 100; });
-  EXPECT_EQ(set.size(), 11);
+  const int64_t removed = set.remove_if([](const int64_t key) { return key > 100; });
+  EXPECT_EQ(set.size() + removed, 100);
   for (const int64_t i : IndexRange(100)) {
     EXPECT_EQ(set.contains(i * i), i <= 10);
   }

source/blender/blenlib/tests/BLI_vector_set_test.cc

@@ -134,8 +134,8 @@ TEST(vector_set, RemoveIf)
   for (const int64_t i : IndexRange(100)) {
     set.add(i * i);
   }
-  set.remove_if([](const int64_t key) { return key % 2 == 0; });
-  EXPECT_EQ(set.size(), 50);
+  const int64_t removed = set.remove_if([](const int64_t key) { return key % 2 == 0; });
+  EXPECT_EQ(set.size() + removed, 100);
   for (const int64_t i : IndexRange(100)) {
     EXPECT_EQ(set.contains(i * i), i % 2 == 1);
   }

source/blender/blenlib/tests/BLI_vector_test.cc

@@ -422,7 +422,8 @@ TEST(vector, Remove)
 TEST(vector, RemoveIf)
 {
   Vector<int> vec = {1, 2, 3, 4, 5, 6, 7, 8};
-  vec.remove_if([](const int x) { return x % 2 == 0; });
+  const int64_t removed = vec.remove_if([](const int x) { return x % 2 == 0; });
+  EXPECT_EQ(vec.size() + removed, 8);
   const Vector<int> expected_vec = {1, 3, 5, 7};
   EXPECT_EQ(vec.size(), expected_vec.size());
   EXPECT_EQ_ARRAY(vec.data(), expected_vec.data(), size_t(vec.size()));