sets: implement a RemoveFunc() for removing elements matching a condi…

…tion (#26)

README.md

@@ -54,6 +54,7 @@ Implements the following set operations
 - Remove
 - RemoveAll
 - RemoveSet
+- RemoveFunc
 - Contains
 - ContainsAll
 - Subset

hashset.go

@@ -127,6 +127,20 @@ func (s *HashSet[T, H]) RemoveSet(o *HashSet[T, H]) bool {
 	return modified
 }
 
+// RemoveFunc will remove each element from s that satisfies condition f.
+//
+// Return true if s was modified, false otherwise.
+func (s *HashSet[T, H]) RemoveFunc(f func(item T) bool) bool {
+	modified := false
+	for _, item := range s.items {
+		if applies := f(item); applies {
+			s.Remove(item)
+			modified = true
+		}
+	}
+	return modified
+}
+
 // Contains returns whether item is present in s.
 func (s *HashSet[T, H]) Contains(item T) bool {
 	_, exists := s.items[item.Hash()]

hashset_test.go

@@ -204,6 +204,47 @@ func TestHashSet_RemoveSet(t *testing.T) {
 	})
 }
 
+func TestHashSet_RemoveFunc(t *testing.T) {
+	t.Run("empty", func(t *testing.T) {
+		s := NewHashSet[*company, string](10)
+		modified := s.RemoveFunc(func(c *company) bool {
+			return c.floor > 3
+		})
+		must.Empty(t, s)
+		must.False(t, modified)
+	})
+
+	t.Run("none match", func(t *testing.T) {
+		s := HashSetFrom[*company, string]([]*company{c1, c2, c3})
+		modified := s.RemoveFunc(func(c *company) bool {
+			return c.floor > 3
+		})
+		must.False(t, modified)
+		must.Size(t, 3, s)
+	})
+
+	t.Run("some match", func(t *testing.T) {
+		s := HashSetFrom[*company, string]([]*company{c1, c2, c3, c4, c5, c6})
+		modified := s.RemoveFunc(func(c *company) bool {
+			return c.floor > 3
+		})
+		must.True(t, modified)
+		must.Size(t, 3, s)
+		must.Contains[*company](t, c1, s)
+		must.Contains[*company](t, c2, s)
+		must.Contains[*company](t, c3, s)
+	})
+
+	t.Run("all match", func(t *testing.T) {
+		s := HashSetFrom[*company, string]([]*company{c1, c2, c3, c4, c5, c6})
+		modified := s.RemoveFunc(func(c *company) bool {
+			return c.floor >= 0
+		})
+		must.True(t, modified)
+		must.Empty(t, s)
+	})
+}
+
 func TestHashSet_Contains(t *testing.T) {
 	t.Run("empty contains", func(t *testing.T) {
 		a := NewHashSet[*company, string](0)

set.go

@@ -135,6 +135,20 @@ func (s *Set[T]) RemoveSet(o *Set[T]) bool {
 	return modified
 }
 
+// RemoveFunc will remove each element from s that satisfies condition f.
+//
+// Return true if s was modified, false otherwise.
+func (s *Set[T]) RemoveFunc(f func(item T) bool) bool {
+	modified := false
+	for item := range s.items {
+		if applies := f(item); applies {
+			s.Remove(item)
+			modified = true
+		}
+	}
+	return modified
+}
+
 // Contains returns whether item is present in s.
 func (s *Set[T]) Contains(item T) bool {
 	_, exists := s.items[item]

set_test.go

@@ -412,6 +412,44 @@ func TestSet_RemoveSet(t *testing.T) {
 	})
 }
 
+func TestSet_RemoveFunc(t *testing.T) {
+	t.Run("empty", func(t *testing.T) {
+		a := New[int](10)
+		modified := a.RemoveFunc(func(i int) bool {
+			return i%2 == 0
+		})
+		must.Empty(t, a)
+		must.False(t, modified)
+	})
+
+	t.Run("none match", func(t *testing.T) {
+		a := From[int]([]int{1, 3, 5, 7, 9})
+		modified := a.RemoveFunc(func(i int) bool {
+			return i%2 == 0
+		})
+		must.True(t, a.ContainsSlice([]int{1, 3, 5, 7, 9}))
+		must.False(t, modified)
+	})
+
+	t.Run("some match", func(t *testing.T) {
+		a := From[int]([]int{1, 2, 3, 4, 5, 6, 7, 8, 9})
+		modified := a.RemoveFunc(func(i int) bool {
+			return i%2 == 0
+		})
+		must.True(t, a.ContainsSlice([]int{1, 3, 5, 7, 9}))
+		must.True(t, modified)
+	})
+
+	t.Run("all match", func(t *testing.T) {
+		a := From[int]([]int{1, 3, 5, 7, 9})
+		modified := a.RemoveFunc(func(i int) bool {
+			return i%2 != 0
+		})
+		must.Empty(t, a)
+		must.True(t, modified)
+	})
+}
+
 func TestSet_Copy(t *testing.T) {
 	t.Run("copy empty", func(t *testing.T) {
 		a := New[int](0)