-;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile
-;;;; written by Michael Livshin <mike@olan.com>
+;;;; and-let-star.scm --- and-let* syntactic form (SRFI-2) for Guile
;;;;
-;;;; Copyright (C) 1999, 2001, 2004, 2006 Free Software Foundation, Inc.
+;;;; Copyright (C) 1999, 2001, 2004, 2006, 2013 Free Software Foundation, Inc.
;;;;
;;;; 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 2.1 of the License, or (at your option) any later version.
+;;;; 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
(define-module (ice-9 and-let-star)
:export-syntax (and-let*))
-(defmacro and-let* (vars . body)
+(define-syntax %and-let*
+ (lambda (form)
+ (syntax-case form ()
+ ((_ orig-form ())
+ #'#t)
+ ((_ orig-form () body bodies ...)
+ #'(begin body bodies ...))
+ ((_ orig-form ((var exp) c ...) body ...)
+ (identifier? #'var)
+ #'(let ((var exp))
+ (and var (%and-let* orig-form (c ...) body ...))))
+ ((_ orig-form ((exp) c ...) body ...)
+ #'(and exp (%and-let* orig-form (c ...) body ...)))
+ ((_ orig-form (var c ...) body ...)
+ (identifier? #'var)
+ #'(and var (%and-let* orig-form (c ...) body ...)))
+ ((_ orig-form (bad-clause c ...) body ...)
+ (syntax-violation 'and-let* "Bad clause" #'orig-form #'bad-clause)))))
- (define (expand vars body)
- (cond
- ((null? vars)
- (if (null? body)
- #t
- `(begin ,@body)))
- ((pair? vars)
- (let ((exp (car vars)))
- (cond
- ((pair? exp)
- (cond
- ((null? (cdr exp))
- `(and ,(car exp) ,(expand (cdr vars) body)))
- (else
- (let ((var (car exp)))
- `(let (,exp)
- (and ,var ,(expand (cdr vars) body)))))))
- (else
- `(and ,exp ,(expand (cdr vars) body))))))
- (else
- (error "not a proper list" vars))))
-
- (expand vars body))
+(define-syntax and-let*
+ (lambda (form)
+ (syntax-case form ()
+ ((_ (c ...) body ...)
+ #`(%and-let* #,form (c ...) body ...)))))
(cond-expand-provide (current-module) '(srfi-2))