isupeene/sparse-matrix — pull request #12 by bsoetaer (2014-09-26 04:44:52+00:00)
Title: Arithmetic contracts

Created the arithmetic contracts. test_exp fails because it tries to call the scalar * because matrix identity function creates a scalar.

Problems encountered with the sub and add operations that have not yet been fixed.
Running the following:
irb
```ruby
require "matrix"
require "matrix_test"
abc = Matrix[[1,2],[3,4]]
abc + 1 # this works and calls the preconditions
abc + 1 # this does not call the preconditions
abc - 1 # this does not call the preconditions
ghi = Matrix[[1,2]]
ghi - 1 # this does not call the preconditions either
```