ice-9/and-let-star.scm

   1 ;;;; and-let-star.scm --- and-let* syntactic form (draft SRFI-2) for Guile
   2 ;;;; written by Michael Livshin <mike@olan.com>
   3 ;;;;
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  44
  45 (define-module (ice-9 and-let-star)
  46   :export-syntax (and-let*))
  47
  48 (defmacro and-let* (vars . body)
  49
  50   (define (expand vars body)
  51     (cond
  52      ((null? vars)
  53       `(begin ,@body))
  54      ((pair? vars)
  55       (let ((exp (car vars)))
  56         (cond
  57          ((pair? exp)
  58           (cond
  59            ((null? (cdr exp))
  60             `(and ,(car exp) ,(expand (cdr vars) body)))
  61            (else
  62             (let ((var (car exp))
  63                   (val (cadr exp)))
  64               `(let (,exp)
  65                  (and ,var ,(expand (cdr vars) body)))))))
  66          (else
  67           `(and ,exp ,(expand (cdr vars) body))))))
  68      (else
  69       (error "not a proper list" vars))))
  70
  71   (expand vars body))