rica.column
The `column` namespace contains an implementation of a Column data strucutre
and functions to help create Columns out of other collections.
A Column is simply a typed PersistentVector that allows nils.
column-type
(column-type col)
Returns the type of the given column. All elements in the column are either
this type or nil.
column-type-mismatch
(column-type-mismatch actual-dtype expected-dtype)
create-column
(create-column coll dtype)(create-column coll)
Creates a new Column containing the contents of coll. The type of the
Column's contents can either be given (dytpe) or infered. If a column type
is infered from a collection with all nils, java.lang.Boolean is used.
A Column is a indexed structure whose elements are all either nil or the same
type.