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75 lines
3 KiB
Scheme
75 lines
3 KiB
Scheme
;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile
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;;;; written by Michael Livshin <mike@olan.com>
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;;;;
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;;;; Copyright (C) 1999, 2001, 2004 Free Software Foundation, Inc.
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;;;;
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;;;; This program is free software; you can redistribute it and/or modify
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;;;; it under the terms of the GNU General Public License as published by
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;;;; the Free Software Foundation; either version 2, or (at your option)
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;;;; any later version.
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;;;;
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;;;; This program is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;;; GNU General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU General Public License
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;;;; along with this software; see the file COPYING. If not, write to
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;;;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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;;;; Boston, MA 02110-1301 USA
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;;;;
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;;;; As a special exception, the Free Software Foundation gives permission
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;;;; for additional uses of the text contained in its release of GUILE.
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;;;;
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;;;; The exception is that, if you link the GUILE library with other files
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;;;; to produce an executable, this does not by itself cause the
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;;;; resulting executable to be covered by the GNU General Public License.
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;;;; Your use of that executable is in no way restricted on account of
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;;;; linking the GUILE library code into it.
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;;;;
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;;;; This exception does not however invalidate any other reasons why
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;;;; the executable file might be covered by the GNU General Public License.
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;;;;
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;;;; This exception applies only to the code released by the
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;;;; Free Software Foundation under the name GUILE. If you copy
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;;;; code from other Free Software Foundation releases into a copy of
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;;;; GUILE, as the General Public License permits, the exception does
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;;;; not apply to the code that you add in this way. To avoid misleading
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;;;; anyone as to the status of such modified files, you must delete
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;;;; this exception notice from them.
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;;;;
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;;;; If you write modifications of your own for GUILE, it is your choice
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;;;; whether to permit this exception to apply to your modifications.
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;;;; If you do not wish that, delete this exception notice.
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(define-module (ice-9 and-let-star)
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:export-syntax (and-let*))
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(defmacro and-let* (vars . body)
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(define (expand vars body)
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(cond
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((null? vars)
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(if (null? body)
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#t
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`(begin ,@body)))
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((pair? vars)
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(let ((exp (car vars)))
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(cond
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((pair? exp)
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(cond
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((null? (cdr exp))
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`(and ,(car exp) ,(expand (cdr vars) body)))
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(else
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(let ((var (car exp))
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(val (cadr exp)))
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`(let (,exp)
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(and ,var ,(expand (cdr vars) body)))))))
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(else
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`(and ,exp ,(expand (cdr vars) body))))))
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(else
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(error "not a proper list" vars))))
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(expand vars body))
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(cond-expand-provide (current-module) '(srfi-2))
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