Checkpoint

internal/sliceutil/filter.go

@@ -0,0 +1,70 @@
+package sliceutil
+
+// AppendFilter takes two slice, 's' as source and 'd' as destination
+// and a predicate function, then applies it to each element of 's',
+// when 'p' returns true it appends the element into d, otherwise omit it.
+func AppendFilter[T any](s []T, d *[]T, p func(T) bool) {
+	for _, e := range s {
+		if p(e) {
+			*d = append(*d, e)
+		}
+	}
+}
+
+// AssignFilter takes two slice, 's' as source and 'd' as destination
+// and a predicate function, then applies it to each element of 's'.
+// 'd' slice will have the same capacity of 's' but starts with 0 length.
+// When 'p' returns true it appends the element into d, otherwise omit it.
+func AssignFilter[T any](s []T, d *[]T, p func(T) bool) {
+	if cap(*d) == 0 {
+		*d = make([]T, 0, len(s))
+	}
+	for _, e := range s {
+		if p(e) {
+			*d = append(*d, e)
+		}
+	}
+}
+
+// DisposeFilter takes two slice, 's' as source and 'd' as destination
+// and a predicate function, then applies it to each element of 's'.
+// 'd' slice will share the exact same memory address of 's'.
+// When 'p' returns true it appends the element into d, otherwise omit it.
+// Then disposes the 's'. IMPORTANT: 's' cannot be used again.
+func DisposeFilter[T any](s []T, d *[]T, p func(T) bool) {
+	*d = s[:0]
+	for _, e := range s {
+		if p(e) {
+			*d = append(*d, e)
+		}
+	}
+	var NIL T
+	for i := len(*d); i < len(s); i++ {
+		s[i] = NIL
+	}
+}
+
+// InPlaceFilter takes a slice and a predicate function, then applies it to each element of 's'.
+// When 'p' returns true it assign the value to the last index plus one where p was true, otherwise omit it.
+func InPlaceFilter[T any](s *[]T, p func(T) bool) {
+	i := 0
+	for _, e := range *s {
+		if p(e) {
+			(*s)[i] = e
+			i++
+		}
+	}
+	*s = (*s)[:i]
+}
+
+// Filter takes a slice and a predcate function, then applies it to each element of 's'.
+// When 'p' returns true it appends the value to the output slice.
+func Filter[T any](s []T, p func(T) bool) []T {
+	o := make([]T, 0, len(s))
+	for _, e := range s {
+		if p(e) {
+			o = append(o, e)
+		}
+	}
+	return o
+}