sympy/sympy — pull request #1121 by mrocklin (2012-03-14 16:46:13+00:00)
Title: Matrix creation

This pull request cleans up matrix creation. Particularly the following behaviors were changed

x = Matrix(2,2, range(4))

Matrix(x) is x # this is now False, used to be True

X = MatrixSymbol('X', 2, 2)

Matrix(X) # this is now a dense mutable Matrix.

I think that the Matrix(MatExpr) change should replace the as_mutable/as_explicit syntax .

Additionally the _handle_creation_inputs method in MatrixBase was cleaned up a bit.