What is Piping?

Piping is a small library providing mechanisms to create message passing pipeline constructs.

How To

Load Piping through Quicklisp or ASDF:

(ql:quickload :piping)

Create a pipeline and add some pipe segments:

(defvar *pipeline* (make-instance 'pipeline))
(add-segment *pipeline* (make-instance 'predicate-filter :predicate #'evenp))
(add-segment *pipeline* (make-instance 'printer))

Using pass you can then pass items down the pipeline:

(pass *pipeline* 7)
(pass *pipeline* 6)

Often times you'll want to create pipe branches so to speak, to split off passing and to filter for different things:

(add-segment *pipeline* (make-pipe))
(add-segment *pipeline* (make-instance 'predicate-filter :predicate #'zerop) '(2))
(add-segment *pipeline* (make-instance 'printer) '(2))

The last argument to add-segment is a place indicator. A place is always a list of indexes, each index specifying the index within the current pipe. add-segment then adds the segment to the end of the pipe, in this case the pipe we added.

In order to have easier access to places, you can use set-name to create names for certain places. Do note that modifying the pipeline might change or destroy names. See the each function's docstring for more information.

Creating custom pipe segments is just a question of subclassing segment and defining the pass method. If your segment should act like a pipe, you'll have to define methods for find-place, find-parent, insert and withdraw as well.

Visualizing the pipeline can be done relatively well by simply printing the main pipe:

(pipeline *pipeline*)
; ==> #(:FILTER: >>FAUCET #(:FILTER: >>FAUCET)