| ;;; ck, to facilitate applicative-order macro programming | |
| ;;; Copyright (C) 2012 Free Software Foundation, Inc | |
| ;;; Copyright (C) 2009, 2011 Oleg Kiselyov | |
| ;;; | |
| ;;; This library is free software; you can redistribute it and/or | |
| ;;; modify it under the terms of the GNU Lesser General Public | |
| ;;; License as published by the Free Software Foundation; either | |
| ;;; version 3 of the License, or (at your option) any later version. | |
| ;;; | |
| ;;; This library is distributed in the hope that it will be useful, | |
| ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| ;;; Lesser General Public License for more details. | |
| ;;; | |
| ;;; You should have received a copy of the GNU Lesser General Public | |
| ;;; License along with this library; if not, write to the Free Software | |
| ;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
| ;;; | |
| ;;; | |
| ;;; Originally written by Oleg Kiselyov and later contributed to Guile. | |
| ;;; | |
| ;;; Based on the CK machine introduced in: | |
| ;;; | |
| ;;; Matthias Felleisen and Daniel P. Friedman: Control operators, the | |
| ;;; SECD machine, and the lambda-calculus. In Martin Wirsing, editor, | |
| ;;; Formal Description of Programming Concepts III, pages | |
| ;;; 193-217. Elsevier, Amsterdam, 1986. | |
| ;;; | |
| ;;; See http://okmij.org/ftp/Scheme/macros.html#ck-macros for details. | |
| ;;; | |
| (define-module (system base ck) | |
| #:export (ck)) | |
| (define-syntax ck | |
| (syntax-rules (quote) | |
| ((ck () 'v) v) ; yield the value on empty stack | |
| ((ck (((op ...) ea ...) . s) 'v) ; re-focus on the other argument, ea | |
| (ck-arg s (op ... 'v) ea ...)) | |
| ((ck s (op ea ...)) ; Focus: handling an application; | |
| (ck-arg s (op) ea ...)))) ; check if args are values | |
| (define-syntax ck-arg | |
| (syntax-rules (quote) | |
| ((ck-arg s (op va ...)) ; all arguments are evaluated, | |
| (op s va ...)) ; do the redex | |
| ((ck-arg s (op ...) 'v ea1 ...) ; optimization when the first ea | |
| (ck-arg s (op ... 'v) ea1 ...)) ; was already a value | |
| ((ck-arg s (op ...) ea ea1 ...) ; focus on ea, to evaluate it | |
| (ck (((op ...) ea1 ...) . s) ea)))) | |