+++ /dev/null
-;;;; -*- Mode: Lisp; Syntax: ANSI-Common-Lisp; Base: 10 -*-
-;;;; *************************************************************************
-;;;; FILE IDENTIFICATION
-;;;;
-;;;; Name: pipes.lisp
-;;;; Purpose: Pipes based on ideas from Norvig's PAIP book
-;;;; Programmers: Kevin M. Rosenberg and Peter Norvig
-;;;; Date Started: Apr 2000
-;;;;
-;;;; $Id: pipes.lisp,v 1.3 2002/11/08 16:51:40 kevin Exp $
-;;;;
-;;;; This file is Copyright (c) 2000-2002 by Kevin M. Rosenberg and
-;;;; Copyright (c) 1998-2002 by Peter Norvig.
-;;;; *************************************************************************
-
-(in-package :pipes)
-
-
-(defconstant +empty-pipe+ nil)
-
-(defmacro make-pipe (head tail)
- "Create a pipe by evaluating head and delaying tail."
- `(cons ,head #'(lambda () ,tail)))
-
-(defun pipe-tail (pipe)
- "Return tail of pipe or list, and destructively update
- the tail if it is a function."
- (if (functionp (rest pipe))
- (setf (rest pipe) (funcall (rest pipe)))
- (rest pipe)))
-
-(defun pipe-head (pipe) (first pipe))
-
-(defun pipe-elt (pipe i)
- "The i-th element of pipe, 0-based."
- (if (= i 0)
- (pipe-head pipe)
- (pipe-elt (pipe-tail pipe) (- i 1))))
-
-
-(defun pipe-enumerate (pipe &key count key (result pipe))
- "Go through all (or count) elements of pipe,
- possibly applying the KEY function. (Try PRINT.)"
- ;; Returns RESULT, which defaults to the pipe itself.
- (if (or (eq pipe +empty-pipe+) (eql count 0))
- result
- (progn
- (unless (null key) (funcall key (pipe-head pipe)))
- (pipe-enumerate (pipe-tail pipe)
- :count (if count (1- count))
- :key key :result result))))
-
-(defun pipe-values (pipe &optional count)
- "Simple wrapper to return values of a pipe"
- (pipe-enumerate pipe :count count))
-
-(defun pipe-force (pipe)
- "Force the enumeration of all of the pipe. Never returns
-if the pipe is infinite in length."
- (pipe-enumerate pipe))
-
-(defun pipe-filter (predicate pipe)
- "Keep only items in pipe satisfying predicate."
- (if (eq pipe +empty-pipe+)
- +empty-pipe+
- (let ((head (pipe-head pipe))
- (tail (pipe-tail pipe)))
- (if (funcall predicate head)
- (make-pipe head (pipe-filter predicate tail))
- (pipe-filter predicate tail)))))
-
-
-(defun pipe-map (fn pipe)
- "Map fn over pipe, delaying all but the first fn call."
- (if (eq pipe +empty-pipe+)
- +empty-pipe+
- (make-pipe (funcall fn (pipe-head pipe))
- (pipe-map fn (pipe-tail pipe)))))
-
-
-(defun pipe-map-filtering (fn pipe &optional filter-pred)
- "Map fn over pipe, delaying all but the first fn call,
- while filtering results."
- (if (eq pipe +empty-pipe+)
- +empty-pipe+
- (let* ((head (pipe-head pipe))
- (tail (pipe-tail pipe))
- (result (funcall fn head)))
- (if (or (and filter-pred (funcall filter-pred result))
- result)
- (make-pipe result (pipe-map-filtering fn tail filter-pred))
- (pipe-map-filtering fn tail filter-pred)))))
-
-
-(defun pipe-append (x y)
- "Return a pipe that appends the elements of x and y."
- (if (eq x +empty-pipe+)
- y
- (make-pipe (pipe-head x)
- (pipe-append (pipe-tail x) y))))
-
-
-(defun pipe-mappend (fn pipe)
- "Lazily map fn over pipe, appending results."
- (if (eq pipe +empty-pipe+)
- +empty-pipe+
- (let ((x (funcall fn (pipe-head pipe))))
- (make-pipe (pipe-head x)
- (pipe-append (pipe-tail x)
- (pipe-mappend fn (pipe-tail pipe)))))))
-
-(defun pipe-mappend-filtering (fn pipe &optional filter-pred)
- "Map fn over pipe, delaying all but the first fn call,
- appending results while filtering."
- (if (eq pipe +empty-pipe+)
- +empty-pipe+
- (let* ((head (pipe-head pipe))
- (tail (pipe-tail pipe))
- (result (funcall fn head)))
- (if (or (and filter-pred (funcall filter-pred result))
- result)
- (make-pipe (pipe-head result)
- (pipe-append (pipe-tail result)
- (pipe-mappend-filtering fn tail filter-pred)))
- (pipe-mappend-filtering fn tail filter-pred)))))
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