Transform matrix A into reduced row echelon form this function is written along the lines of the rref-matlab function.
rref(A, tol = sqrt(.Machine$double.eps), verbose = FALSE,
fractions = FALSE)matrix for which the reduced row echelon form is searched
tolerance to find pivots
logical, print verbose information
logical, not used right now.
a list of two entries is returned; ret[[1]] is the reduced row echelon form of A, ret[[2]] is the index of columns in which a pivot was found