diff --git a/tensor.cc b/tensor.cc
index 973dc88..ac30ef3 100644
--- a/tensor.cc
+++ b/tensor.cc
@@ -158,6 +158,27 @@ LA_largeindex Tensor<T>::vindex(int *sign,  int i1, va_list args) const
 }
 
 
+//binary I/O
+
+template<typename T>
+void Tensor<T>::put(int fd) const
+{
+shape.put(fd,true);
+cumsizes.put(fd,true);
+data.put(fd,true);
+}
+
+template<typename T>
+void Tensor<T>::get(int fd)
+{
+shape.get(fd,true);
+cumsizes.get(fd,true);
+data.get(fd,true);
+}
+
+
+
+
 template class Tensor<double>;
 template class Tensor<std::complex<double> >;
 
diff --git a/tensor.h b/tensor.h
index 103cc9c..fc44419 100644
--- a/tensor.h
+++ b/tensor.h
@@ -43,8 +43,12 @@ T *ptr;
 int sgn;
 public:
 	Signedpointer(T *p, int s) : ptr(p),sgn(s) {};
-	T& operator=(const T rhs) {if(sgn==0) return *ptr; if(sgn>0) *ptr=rhs; else *ptr = -rhs; return *ptr;}
-//@@@@@@operations like += etc. on singedpointer as LHS of the non-const tensor.operator() expressions
+	//dereferencing *ptr  should intentionally segfault for sgn==0
+	T& operator=(const T rhs) {if(sgn>0) *ptr=rhs; else *ptr = -rhs; return *ptr;}
+	T& operator*=(const T rhs) {*ptr *= rhs; return *ptr;}
+	T& operator/=(const T rhs) {*ptr /= rhs; return *ptr;}
+	T& operator+=(const T rhs) {if(sgn>0) *ptr += rhs; else *ptr -= rhs; return *ptr;}
+	T& operator-=(const T rhs) {if(sgn>0) *ptr -= rhs; else *ptr += rhs; return *ptr;}
 };
 
 
@@ -65,6 +69,11 @@ class LA_traits<indexgroup> {
 	static bool is_plaindata() {return true;};
 	static void copyonwrite(indexgroup& x) {};
 	typedef INDEXGROUP normtype;
+        static inline void put(int fd, const indexgroup &x, bool dimensions=1) {if(sizeof(indexgroup)!=write(fd,&x,sizeof(indexgroup))) laerror("write error 1 in indexgroup put"); }
+        static inline void multiput(int nn, int fd, const indexgroup *x, bool dimensions=1) {if(nn*sizeof(indexgroup)!=write(fd,x,nn*sizeof(indexgroup))) laerror("write error 1 in indexgroup multiiput"); }
+        static inline void get(int fd, indexgroup &x, bool dimensions=1) {if(sizeof(indexgroup)!=read(fd,&x,sizeof(indexgroup))) laerror("read error 1 in indexgroup get");}
+        static inline void multiget(int nn, int fd, indexgroup *x, bool dimensions=1) {if(nn*sizeof(indexgroup)!=read(fd,x,nn*sizeof(indexgroup))) laerror("read error 1 in indexgroup get");}
+
 };
 
 
@@ -74,13 +83,10 @@ typedef NRVec<NRVec<LA_index> > SUPERINDEX; //all indices in the INDEXGROUP stru
 
 template<typename T>
 class Tensor {
-//essential data
 	NRVec<indexgroup> shape;
+	NRVec<LA_largeindex> cumsizes; //cumulative sizes of symmetry index groups (a function of shape but precomputed for efficiency)
 	NRVec<T> data;	
 
-//redundant data to facilitate efficient indexing
-	NRVec<LA_largeindex> cumsizes; //cumulative sizes of symmetry index groups
-
 private:
 	LA_largeindex index(int *sign, const SUPERINDEX &I) const; //map the tensor indices to the position in data
 	LA_largeindex index(int *sign, const  FLATINDEX &I) const; //map the tensor indices to the position in data
@@ -102,14 +108,18 @@ public:
         inline T operator()(const FLATINDEX &I) {int sign; LA_largeindex i=index(&sign,I); if(sign==0) return 0; return sign>0 ?data[i] : -data[i];};
         inline Signedpointer<T> lhs(int i1...) {va_list args; int sign; LA_largeindex i; va_start(args,i1); i= vindex(&sign, i1,args);  return Signedpointer<T>(&data[i],sign); };
         inline T operator()(int i1...) {va_list args; ; int sign; LA_largeindex i; va_start(args,i1);  i= vindex(&sign, i1,args); if(sign==0) return 0; return sign>0 ?data[i] : -data[i];};
-
-	//NOTE: for sign==0 data[i]  can be undefined pointer, avoid dereferencing it
 	
 	inline Tensor& operator*=(const T &a) {data*=a; return *this;};
+	inline Tensor& operator/=(const T &a) {data/=a; return *this;};
+
+	void put(int fd) const;
+	void get(int fd);
 
 	//@@@TODO - unwinding to full size in a specified index
 	//@@@TODO - contractions - basic and efficient
-	//@@@TODO get/put to file, stream i/o
+	//@@@dodelat indexy
+	//@@@ dvojite rekurzivni loopover s callbackem - nebo iterator s funkci next???
+	//@@@ stream i/o na zaklade tohoto
 };