1 files changed, 72 insertions, 0 deletions
diff --git a/common/predicate/predicate.go b/common/predicate/predicate.go
new file mode 100644
index 000000000..f9cb1bb2b
--- /dev/null
+++ b/common/predicate/predicate.go
@@ -0,0 +1,72 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package predicate
+
+// P is a predicate function that tests whether a value of type T satisfies some condition.
+type P[T any] func(T) bool
+
+// And returns a predicate that is a short-circuiting logical AND of this and the given predicates.
+func (p P[T]) And(ps ...P[T]) P[T] {
+	return func(v T) bool {
+		for _, pp := range ps {
+			if !pp(v) {
+				return false
+			}
+		}
+		return p(v)
+	}
+}
+
+// Or returns a predicate that is a short-circuiting logical OR of this and the given predicates.
+func (p P[T]) Or(ps ...P[T]) P[T] {
+	return func(v T) bool {
+		for _, pp := range ps {
+			if pp(v) {
+				return true
+			}
+		}
+		return p(v)
+	}
+}
+
+// Negate returns a predicate that is a logical negation of this predicate.
+func (p P[T]) Negate() P[T] {
+	return func(v T) bool {
+		return !p(v)
+	}
+}
+
+// Filter returns a new slice holding only the elements of s that satisfy p.
+// Filter modifies the contents of the slice s and returns the modified slice, which may have a smaller length.
+func (p P[T]) Filter(s []T) []T {
+	var n int
+	for _, v := range s {
+		if p(v) {
+			s[n] = v
+			n++
+		}
+	}
+	return s[:n]
+}
+
+// FilterCopy returns a new slice holding only the elements of s that satisfy p.
+func (p P[T]) FilterCopy(s []T) []T {
+	var result []T
+	for _, v := range s {
+		if p(v) {
+			result = append(result, v)
+		}
+	}
+	return result
+}