  Recently, the tensor network states (TNS) methods have proven to be very
powerful tools to investigate the strongly correlated many-particle physics in
one and two dimensions. The implementation of TNS methods depends heavily on
the operations of tensors, including contraction, permutation, reshaping
tensors, SVD and son on. Unfortunately, the most popular computer languages for
scientific computation, such as Fortran and C/C++ do not have a standard
library for such operations, and therefore make the coding of TNS very tedious.
We develop a Fortran2003 package that includes all kinds of basic tensor
operations designed for TNS. It is user-friendly and flexible for different
forms of TNS, and therefore greatly simplifies the coding work for the TNS
methods.
