View Compilation Error

0_0_4062013_27216.cpp: In function `T getPower(T&, int) [with T = Matrix]':
0_0_4062013_27216.cpp:90:   instantiated from here
0_0_4062013_27216.cpp:48: error: invalid initialization of non-const reference of type 'Matrix&' from a temporary of type 'Matrix'
0_0_4062013_27216.cpp:40: error: in passing argument 1 of `T square(T&) [with T = Matrix]'