ContinuumIO/blaze — pull request #319 by mrocklin (2014-06-06 19:53:30+00:00)
Title: Scalar Expressions

See major issue #281

Introduces a new scalar expression system. Now instead of `Add`, `Mul`, `sin`, `exp` being of type `ColumnWise` they are now of type `ScalarExpr`. `ColumnWise` has graduated from being an abstract class to a concrete one which contains a scalar expr and a sequence of columnar arguments.

Along with this comes some efficiencies.

1. Python streaming split-apply-combine is now able to handle much more general problems (although I think we actually could have managed this without this change).
2. This will also be essential for non-trivial Spark solutions.
3. This will make a transition to array exprs simpler
4. There was some nice refactoring along the way.