Simulated cin input

lc provides a mechanism which allows the user to enter objects in the same way as in library mode, i.e. when using the cin operator. This is done using a cast from the string type. For example (quadratic_form) "(1 2 3)"; is a valid input for a quadratic form. In the same way, (rational_factorization) "[(2,3) (3,7)]"; is a valid input for factorization object.