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46 lines
1.6 KiB
Scheme
46 lines
1.6 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 Free Software Foundation, Inc.
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;;;;
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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;;;; License as published by the Free Software Foundation; either
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;;;; version 2.1 of the License, or (at your option) any later version.
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;;;;
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;;;; This library 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 GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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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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`(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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