[Help-gsl] return value of matrix operations

[kamaraju kusumanchi]

I am a bit confused about where the result of a matrix operation
function is stored. For example consider gsl_matrix_add as described
in http://www.gnu.org/software/gsl/manual/html_node/Matrix-operations.html.

Function: int gsl_matrix_add (gsl_matrix * a, const gsl_matrix * b)

    This function adds the elements of matrix b to the elements of
matrix a, a'(i,j) = a(i,j) + b(i,j). The two matrices must have the
same dimensions.

Where is the result a' stored? Is it overwritten on a or b? Also the
function is returning an integer. So it can't be a', right?

I tried poking into gsl (1.11) source code on my Debian Stable (Lenny)
system. I found the function declarations in
matrix/gsl_matrix_double.h . But I could not find the actual function
definition. Can someone help me locate that as well?