a quick method to compute modulo n with rounding towards -infinity.
addition of discrete module.
a method to extract a row vector.
predicates is_row and is_col
is_scalar predicate
split the sub-matrix extraction and vector/scalar conversion functions into a separate impl block.  implemented column extraction function.
a function to extrtact a sub matrix from a matrix.
function for repeating a matrix.
Introduced matelt.rs and materr.rs simplified code in matrix.rs
main.rs need not be tracked.
main.rs will no longer be tracked. This is used only for writing experimental code. Actual production code is in library , unit tests and the examples that would appear in future.