diff --git a/src_main/containers/pideque.h b/src_main/containers/pideque.h
index dd2e3d3c..3a4d7c21 100755
--- a/src_main/containers/pideque.h
+++ b/src_main/containers/pideque.h
@@ -370,7 +370,12 @@ public:
 	}
 
 #ifdef PIP_CXX11_SUPPORT
-	PIDeque<T> forEach(std::function<T(const T &)> f) const {
+	const PIDeque<T> & forEach(std::function<void(const T &)> f) const {
+		for (uint i = 0; i < pid_size; ++i)
+			f(pid_data[i + pid_start]);
+		return *this;
+	}
+	PIDeque<T> copyForEach(std::function<T(const T &)> f) const {
 		PIDeque<T> ret; ret.reserve(pid_size);
 		for (uint i = 0; i < pid_size; ++i)
 			ret << f(pid_data[i + pid_start]);
diff --git a/src_main/containers/pivector.h b/src_main/containers/pivector.h
index 583e8980..41d7082c 100755
--- a/src_main/containers/pivector.h
+++ b/src_main/containers/pivector.h
@@ -362,7 +362,12 @@ public:
 	}
 
 #ifdef PIP_CXX11_SUPPORT
-	PIVector<T> forEach(std::function<T(const T &)> f) const {
+	const PIVector<T> & forEach(std::function<void(const T &)> f) const {
+		for (uint i = 0; i < piv_size; ++i)
+			f(piv_data[i]);
+		return *this;
+	}
+	PIVector<T> copyForEach(std::function<T(const T &)> f) const {
 		PIVector<T> ret; ret.reserve(piv_size);
 		for (uint i = 0; i < piv_size; ++i)
 			ret << f(piv_data[i]);