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Avoid quadratic expansion time in 'and' and 'or' macros.

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Fixes <http://bugs.gnu.org/17147>.
Reported by David Kastrup <dak@gnu.org>.

* module/ice-9/boot-9.scm (and, or): Use dotted tail instead of ellipsis
  in patterns.
This commit is contained in:
Mark H Weaver 2014-06-04 19:30:16 -04:00
parent 2da97f1c7c
commit 1ea8954814
1 changed files with 5 additions and 5 deletions
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10
module/ice-9/boot-9.scm
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@ -1,8 +1,6 @@
;;; -*- mode: scheme; coding: utf-8; -*- ;;; -*- mode: scheme; coding: utf-8; -*-
;;;; Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, ;;;; Copyright (C) 1995-2014 Free Software Foundation, Inc.
;;;; 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014
;;;; Free Software Foundation, Inc.
;;;; ;;;;
;;;; This library is free software; you can redistribute it and/or ;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public ;;;; modify it under the terms of the GNU Lesser General Public
@ -409,13 +407,15 @@ If there is no handler at all, Guile prints an error and then exits."
(syntax-rules () (syntax-rules ()
((_) #t) ((_) #t)
((_ x) x) ((_ x) x)
((_ x y ...) (if x (and y ...) #f)))) ;; Avoid ellipsis, which would lead to quadratic expansion time.
((_ x . y) (if x (and . y) #f))))
(define-syntax or (define-syntax or
(syntax-rules () (syntax-rules ()
((_) #f) ((_) #f)
((_ x) x) ((_ x) x)
((_ x y ...) (let ((t x)) (if t t (or y ...)))))) ;; Avoid ellipsis, which would lead to quadratic expansion time.
((_ x . y) (let ((t x)) (if t t (or . y))))))
(include-from-path "ice-9/quasisyntax") (include-from-path "ice-9/quasisyntax")