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Diffstat (limited to 'module/system/base/ck.scm')
-rw-r--r-- | module/system/base/ck.scm | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/module/system/base/ck.scm b/module/system/base/ck.scm new file mode 100644 index 000000000..cd9cc18c6 --- /dev/null +++ b/module/system/base/ck.scm @@ -0,0 +1,55 @@ +;;; 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)))) |