diff --git a/src/include/xpr/for.cc.h b/src/include/xpr/for.cc.h
index 488bc2d..1d2edf8 100644
--- a/src/include/xpr/for.cc.h
+++ b/src/include/xpr/for.cc.h
@@ -26,25 +26,42 @@ namespace CNORXZ
     template <class PosT>
     inline decltype(auto) For<L,Xpr,F>::operator()(const PosT& last) const
     {
-	typedef typename std::remove_reference<decltype(mXpr(last + mExt * UPos(0)))>::type OutT;
-	auto o = OutT();
-	for(SizeT i = 0; i != mSize; ++i){
-	    const auto pos = last + mExt * UPos(i);
-	    mF(o, mXpr(pos));
+	if constexpr(std::is_same<F,NoF>::value){
+	    for(SizeT i = 0; i != mSize; ++i){
+		const auto pos = last + mExt * UPos(i);
+		mXpr(pos);
+	    }
+	}
+	else {
+	    typedef typename
+		std::remove_reference<decltype(mXpr(last + mExt * UPos(0)))>::type OutT;
+	    auto o = OutT();
+	    for(SizeT i = 0; i != mSize; ++i){
+		const auto pos = last + mExt * UPos(i);
+		mF(o, mXpr(pos));
+	    }
+	    return o;
 	}
-	return o;
     }
 	
     template <SizeT L, class Xpr, class F>
     inline decltype(auto) For<L,Xpr,F>::operator()() const
     {
-	typedef typename std::remove_reference<decltype(mXpr(mExt * UPos(0)))>::type OutT;
-	auto o = OutT();
-	for(SizeT i = 0; i != mSize; ++i){
-	    const auto pos = mExt * UPos(i);
-	    mF(o, mXpr(pos));
+	if constexpr(std::is_same<F,NoF>::value){
+	    for(SizeT i = 0; i != mSize; ++i){
+		const auto pos = mExt * UPos(i);
+		mXpr(pos);
+	    }
+	}
+	else {
+	    typedef typename std::remove_reference<decltype(mXpr(mExt * UPos(0)))>::type OutT;
+	    auto o = OutT();
+	    for(SizeT i = 0; i != mSize; ++i){
+		const auto pos = mExt * UPos(i);
+		mF(o, mXpr(pos));
+	    }
+	    return o;
 	}
-	return o;
     }
 
     template <SizeT L, class Xpr, class F>
@@ -54,6 +71,21 @@ namespace CNORXZ
 	return mXpr.rootSteps(id);
     }
 
+    /************************
+     *   For (non-member)   *
+     ************************/
+
+    template <SizeT L, class Xpr, class F>
+    constexpr decltype(auto) mkFor(SizeT size, const IndexId<L>& id, const Xpr& xpr, F&& f)
+    {
+	return For<L,Xpr,F>(size, id, xpr, std::forward<F>(f));
+    }
+
+    template <SizeT L, class Xpr>
+    constexpr decltype(auto) mkFor(SizeT size, const IndexId<L>& id, const Xpr& xpr)
+    {
+	return For<L,Xpr>(size, id, xpr, NoF {});
+    }
 
     /************
      *   SFor   *
@@ -63,7 +95,7 @@ namespace CNORXZ
     constexpr SFor<N,L,Xpr,F>::SFor(const IndexId<L>& id, const Xpr& xpr, F&& f) :
 	mId(id),
 	mXpr(xpr),
-	mExt(mXpr.RootSteps(mId)),
+	mExt(mXpr.rootSteps(mId)),
 	mF(f)
     {}
 
@@ -71,13 +103,25 @@ namespace CNORXZ
     template <class PosT>
     constexpr decltype(auto) SFor<N,L,Xpr,F>::operator()(const PosT& last) const
     {
-	return exec<0>(last);
+	if constexpr(std::is_same<F,NoF>::value){
+	    exec2<0>(last);
+	    return;
+	}
+	else {
+	    return exec<0>(last);
+	}
     }
 	
     template <SizeT N, SizeT L, class Xpr, class F>
     constexpr decltype(auto) SFor<N,L,Xpr,F>::operator()() const
     {
-	return exec<0>();
+	if constexpr(std::is_same<F,NoF>::value){
+	    exec2<0>();
+	    return;
+	}
+	else {
+	    return exec<0>();
+	}
     }
 
     template <SizeT N, SizeT L, class Xpr, class F>
@@ -93,12 +137,11 @@ namespace CNORXZ
     {
 	constexpr SPos<I> i;
 	const auto pos = last + mExt * i;
-	auto o = mXpr(pos);
 	if constexpr(I < N-1){
-	    return mF(o,exec<I+1>(last));
+	    return mF(mXpr(pos),exec<I+1>(last));
 	}
 	else {
-	    return o;
+	    return mXpr(pos);
 	}
     }
 
@@ -108,15 +151,62 @@ namespace CNORXZ
     {
 	constexpr SPos<I> i;
 	const auto pos = mExt * i;
-	auto o = mXpr(pos);
 	if constexpr(I < N-1){
-	    return mF(o,exec<I+1>());
+	    return mF(mXpr(pos),exec<I+1>());
 	}
 	else {
-	    return o;
+	    return mXpr(pos);
 	}
     }
 
+    template <SizeT N, SizeT L, class Xpr, class F>
+    template <SizeT I, class PosT>
+    inline void SFor<N,L,Xpr,F>::exec2(const PosT& last) const
+    {
+	constexpr SPos<I> i;
+	const auto pos = last + mExt * i;
+	if constexpr(I < N-1){
+	    mXpr(pos);
+	    exec2<I+1>(last);
+	}
+	else {
+	    mXpr(pos);
+	}
+	return;
+    }
+    
+    template <SizeT N, SizeT L, class Xpr, class F>
+    template <SizeT I>
+    inline void SFor<N,L,Xpr,F>::exec2() const
+    {
+	constexpr SPos<I> i;
+	const auto pos = mExt * i;
+	if constexpr(I < N-1){
+	    mXpr(pos);
+	    exec2<I+1>();
+	}
+	else {
+	    mXpr(pos);
+	}
+	return;
+    }
+
+    /*************************
+     *   SFor (non-member)   *
+     *************************/
+
+    template <SizeT N, SizeT L, class Xpr, class F>
+    constexpr decltype(auto) mkSFor(const IndexId<L>& id, const Xpr& xpr, F&& f)
+    {
+	return SFor<N,L,Xpr,F>(id, xpr, std::forward<F>(f));
+    }
+
+    template <SizeT N, SizeT L, class Xpr>
+    constexpr decltype(auto) mkSFor(const IndexId<L>& id, const Xpr& xpr)
+    {
+	return SFor<N,L,Xpr>(id, xpr, NoF {});
+    }
+    
     /************
      *   TFor   *
      ************/
diff --git a/src/include/xpr/for.h b/src/include/xpr/for.h
index d4ea36c..06709c2 100644
--- a/src/include/xpr/for.h
+++ b/src/include/xpr/for.h
@@ -34,7 +34,12 @@ namespace CNORXZ
 	F mF;
     };
 
-    
+    template <SizeT L, class Xpr, class F>
+    constexpr decltype(auto) mkFor(SizeT size, const IndexId<L>& id, const Xpr& xpr, F&& f);
+
+    template <SizeT L, class Xpr>
+    constexpr decltype(auto) mkFor(SizeT size, const IndexId<L>& id, const Xpr& xpr);
+
     // unrolled loop:
     template <SizeT N, SizeT L, class Xpr, class F = NoF>
     class SFor : public XprInterface<SFor<N,L,Xpr,F>>
@@ -60,14 +65,25 @@ namespace CNORXZ
 	template <SizeT I>
 	constexpr decltype(auto) exec() const;
 
+	template <SizeT I, class PosT>
+	inline void exec2(const PosT& last) const;
+
+	template <SizeT I>
+	inline void exec2() const;
+
 	IndexId<L> mId;
 	Xpr mXpr;
-	typedef decltype(mXpr.RootSteps(mId)) XPosT;
+	typedef decltype(mXpr.rootSteps(mId)) XPosT;
 	XPosT mExt;
 	F mF;
 	
     };
 
+    template <SizeT N, SizeT L, class Xpr, class F>
+    constexpr decltype(auto) mkSFor(const IndexId<L>& id, const Xpr& xpr, F&& f);
+
+    template <SizeT N, SizeT L, class Xpr>
+    constexpr decltype(auto) mkSFor(const IndexId<L>& id, const Xpr& xpr);
 
     // multi-threading
     template <SizeT L, class Xpr, class F = NoF>
diff --git a/src/tests/xpr_unit_test.cc b/src/tests/xpr_unit_test.cc
index bb2280d..8e72fec 100644
--- a/src/tests/xpr_unit_test.cc
+++ b/src/tests/xpr_unit_test.cc
@@ -34,6 +34,73 @@ namespace
 	SPos<ss2> mS2p;
     };
 
+    class For_Test : public ::testing::Test
+    {
+    protected:
+
+	class TestXpr1
+	{
+	public:
+	    constexpr TestXpr1(const IndexId<0>& id) : mId(id) {}
+	    
+	    template <class PosT>
+	    inline SizeT operator()(const PosT& last) const
+	    {
+		const SizeT o = 1u;
+		return o << last.val();
+	    }
+
+	    template <SizeT I>
+	    inline UPos rootSteps(const IndexId<I>& id) const
+	    {
+		return UPos( mId == id ? 1u : 0u );
+	    }
+
+	private:
+	    IndexId<0> mId;
+	};
+
+	class TestXpr2
+	{
+	public:
+	    constexpr TestXpr2(const IndexId<0>& id, SizeT size) :
+		mId(id), mSize(size), mCnt(size) {}
+	    
+	    template <class PosT>
+	    inline void operator()(const PosT& last) const
+	    {
+		--mCnt;
+		EXPECT_EQ(mCnt, mSize-last.val()-1);
+	    }
+
+	    template <SizeT I>
+	    inline UPos rootSteps(const IndexId<I>& id) const
+	    {
+		return UPos( mId == id ? 1u : 0u );
+	    }
+
+	private:
+	    IndexId<0> mId;
+	    SizeT mSize;
+	    mutable SizeT mCnt;
+	};
+
+	static constexpr SizeT sSize = 7u;
+
+	For_Test()
+	{
+	    mSize = sSize;
+	    mId1 = 10u;
+	    mId2 = 11u;
+	    mId3 = 12u;
+	}
+
+	SizeT mSize;
+	PtrId mId1;
+	PtrId mId2;
+	PtrId mId3;
+    };
+    
     TEST_F(Pos_Test, Basics)
     {
 	EXPECT_EQ( mUp1.size(), 1u );
@@ -157,6 +224,37 @@ namespace
 	EXPECT_EQ(dp5.sub().val(), mS4p.val() * mUp1.val());
     }
 
+    TEST_F(For_Test, For)
+    {
+	auto loop = mkFor(mSize, IndexId<0>(mId1), TestXpr1( IndexId<0>(mId1) ),
+			  [](auto& o, const auto& e) { o += e; });
+
+	const UPos rs = loop.rootSteps(IndexId<0>(mId1));
+	EXPECT_EQ(rs.val(), 1u);
+	const UPos rs2 = loop.rootSteps(IndexId<0>(mId2));
+	EXPECT_EQ(rs2.val(), 0u);
+	const SizeT res = loop();
+	EXPECT_EQ(res, (1u << mSize) - 1u);
+
+	auto loop2 = mkFor(mSize, IndexId<0>(mId1), TestXpr2( IndexId<0>(mId1), mSize ));
+	loop2();
+    }
+
+    TEST_F(For_Test, SFor)
+    {
+	auto loop = mkSFor<sSize>(IndexId<0>(mId1), TestXpr1( IndexId<0>(mId1) ),
+				  [](const auto& a, const auto& b) { return a + b; });
+
+	const UPos rs = loop.rootSteps(IndexId<0>(mId1));
+	EXPECT_EQ(rs.val(), 1u);
+	const UPos rs2 = loop.rootSteps(IndexId<0>(mId2));
+	EXPECT_EQ(rs2.val(), 0u);
+	const SizeT res = loop();
+	EXPECT_EQ(res, (1u << mSize) - 1u);
+
+	auto loop2 = mkSFor<sSize>(IndexId<0>(mId1), TestXpr2( IndexId<0>(mId1), mSize ));
+	loop2();
+    }
 }
 
 int main(int argc, char** argv)