#|[
Author: Juergen Lorenz
ju (at) jugilo (dot) de

Copyright (c) 2013, Juergen Lorenz
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

Neither the name of the author nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission. 

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

This module provides simplyfied versions of some of the bindings
macros, restricting destructuring to nested list expressions.
]|# 

(module list-bindings
  (export list-bindings bind-define bind-set! bind bindable? bind-lambda
          bind-case bind/cc bind-let bind-let*)
  (import scheme
          (only chicken condition-case error)
          (only extras format))

(define (list-bindings)
  '(bind-define bind-set! bind bind-lambda bind-let* bind-let bind-case
     bindable? bind/cc))

#|[
Binding macros
==============
]|# 

;;; (bindable? pat)
;;; ---------------
;;; returns a procedure, which checks, if subexpressions of its only
;;; agument, tpl, are bindable to the pattern variables of pat.
(define-syntax bindable?
  (syntax-rules ()
    ((_ (a . b))
     (lambda (seq)
       (and (pair? seq)
            ((bindable? a) (car seq))
            ((bindable? b) (cdr seq)))))
    ((_ ())
     (lambda (seq) (null? seq)))
    ((_ a) (lambda (seq) #t))))

;;; (bind pat seq . body)
;;; --------------------------
;;; Common Lisp's destructuring-bind:
;;; binds pattern variables of pat to corresponding subexpression of
;;; seq and evalueates body in this context
(define-syntax bind
  (syntax-rules ()
    ((_(a . b) lst xpr . xprs)
     (let ((seq lst))
       (if (pair? seq)
         (bind a (car seq) (bind b (cdr seq) xpr . xprs))
         (error 'bind
                (format #f "template ~s doesn't match pattern ~s"
                        seq '(a . b))))))
    ((_ () lst xpr . xprs)
     (let ((seq lst))
       (if (null? seq)
         (let () xpr . xprs)
         (error 'bind
                (format #f "template ~s doesn't match pattern ~s"
                        seq '())))))
    ((_ a lst xpr . xprs)
     (let ((seq lst))
       (let ((a seq)) xpr . xprs)))))

;;; (bind-lambda pat xpr . xprs)
;;; ------------------------------
;;; Combination of bind and lambda
(define-syntax bind-lambda
  (syntax-rules ()
    ((_ pat xpr . xprs)
     (lambda (x)
       (bind pat x xpr . xprs)))))

;;; (bind-case seq (pat xpr . xprs) ....)
;;; -------------------------------------
;;; Checks if seq matches pattern pat in sequence, binds the pattern
;;; variables of the first matching pattern to corresponding sublists of
;;; seq and executes corresponding body xpr . xprs
(define-syntax bind-case
  (syntax-rules ()
    ((_ seq (pat0  xpr0 . xprs0) (pat1 xpr1 . xprs1) ...)
     (cond
       (((bindable? pat0) seq)
        (bind pat0 seq  xpr0 . xprs0))
       (((bindable? pat1) seq)
        (bind pat1 seq  xpr1 . xprs1))
       ...
       (else
         (error 'bind-case (format #f "template ~s doesn't match any of the patterns ~s"
                                   seq '(pat0 pat1 ...))))))))

#|[ 
The next two macros provide simultaneous setting and defining of pattern
variables to subexpressions of a template. The following first try would
perfectly work, if seq is simply a list, but not if it is a list wrapped
by a let storing common state. But the latter is the most often used
case of bind-define.

(define-syntax bind-define
  (syntax-rules ()
    ((_ (a . b) seq)
     (begin
       (bind-define a (car seq))
       (bind-define b (cdr seq))))
    ((_ () seq)
     (if (null? seq) (void) (error 'bind-define "match error")))
    ((_ a seq)
     (define a seq))))

What we need is one further indirection provided in the following
versions, which first map the pattern, pat, to some auxiliary pattern,
aux, of the same form with gensym.
In bind-set! the template, seq, is then bound to some variable x which
in turn can be bound to aux in the macro expansion. Since we used gensym
instead of rename above, there will be no name-clash - rename is
referentially transparent!
We could have used implicit-renaming macros as well, but then the
gensyms would be automatically renamed again, which isn't necessary.
Note, that there is some code duplication in the two macros below, which
could have been avoided by defining two helpers, pmap and pflatten, in a
separate helper module which must be imported for syntax. I've done this
in a former version.
]|#

;;; (bind-set! pat seq)
;;; -------------------
;;; sets pattern variables of the pattern pat to corresponding
;;; subexpressions of the template seq
(define-syntax bind-set!
  (er-macro-transformer
    (lambda (form rename compare?)
      (let ((pat (cadr form)) (seq (caddr form)))
        (let ((aux (let recur ((pat pat))
                     (cond
                       ((null? pat) '())
                       ((symbol? pat) (gensym))
                       ((pair? pat)
                        (cons (recur (car pat)) (recur (cdr pat)))))))
              ; rename would potentially clash with the %x below
              (%bind (rename 'bind))
              (%set! (rename 'set!))
              (%let (rename 'let))
              (%x (rename 'x)))
          `(,%let ((,%x ,seq))
             (,%bind ,aux ,%x
               ,@(let recur ((pat pat) (aux aux))
                   (cond
                     ((null? pat) '())
                     ((symbol? pat) `((set! ,pat ,aux)))
                     ((pair? pat)
                      (append (recur (car pat) (car aux))
                              (recur (cdr pat) (cdr aux)))))))))))))
;(define-syntax bind-set!
;  (ir-macro-transformer
;    (lambda (form inject compare?)
;      (let ((pat (cadr form)) (seq (caddr form)))
;        (let ((aux (pmap gensym pat)))
;          `(let ((x ,seq))
;             (bind ,aux x
;               ,@(map (lambda (p a) `(set! ,p ,a))
;                      (pflatten pat) (pflatten aux)))))))))

;;; (bind-define pat seq)
;;; ---------------------
;;; defines pattern variables of the pattern pat by setting them to
;;; corresponding subexpressions of the template seq
(define-syntax bind-define
  (er-macro-transformer
    (lambda (form rename compare?)
      (let ((pat (cadr form)) (seq (caddr form)))
        (let ((aux (let recur ((pat pat))
                     (cond
                       ((null? pat) '())
                       ((symbol? pat) (gensym))
                       ((pair? pat)
                        (cons (recur (car pat)) (recur (cdr pat)))))))
              (%bind-set! (rename 'bind-set!))
              (%define (rename 'define))
              (%begin (rename 'begin)))
          `(,%begin
             (,%bind-set! ,aux ,seq)
             ,@(let recur ((pat pat) (aux aux))
                 (cond
                   ((null? pat) '())
                   ((symbol? pat) `((set! ,pat ,aux)))
                   ((pair? pat)
                    (append (recur (car pat) (car aux))
                            (recur (cdr pat) (cdr aux))))))))))))
;(define-syntax bind-define
;  (ir-macro-transformer
;    (lambda (form inject compare?)
;      (let ((pat (cadr form)) (seq (caddr form)))
;        (let ((aux (pmap gensym pat)))
;          `(begin
;             (bind-set! ,aux ,seq)
;             ,@(map (lambda (p a) `(define ,p ,a))
;                    (pflatten pat) (pflatten aux))))))))

;;; (bind-let* ((pat seq) ...) xpr . xprs)
;;; --------------------------------------
(define-syntax bind-let*
  (syntax-rules ()
    ((_ () xpr . xprs)
     (let () xpr . xprs))
    ((_ ((pat0 seq0) (pat1 seq1) ...) xpr . xprs)
     (bind pat0 seq0
       (bind-let* ((pat1 seq1) ...) xpr . xprs)))))

;;; (bind-let ((pat seq) ...) xpr . xprs)
;;; -------------------------------------
(define-syntax bind-let
  (ir-macro-transformer
    (lambda (form inject compare?)
      (let ((binds (cadr form))
            (xpr (caddr form))
            (xprs (cdddr form)))
        (let ((syms (map (lambda (x) (gensym)) binds)))
          `(bind ,syms ,(cons 'list (map cadr binds))
             (bind-let* ,(map (lambda (p s) `(,p ,s))
                              (map car binds)
                              syms)
               ,xpr ,@xprs)))))))

;;; (bind/cc k xpr . xprs)
;;; ----------------------
(define-syntax bind/cc
  (syntax-rules ()
    ((_ k xpr . xprs)
     (call-with-current-continuation
       (lambda (k) xpr . xprs)))))

) ; module list-bindings