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Groups > comp.lang.forth > #26429

Re: Starting Forth 6.

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WJ wrote:

> Brodie creates a defining word ARRAY, which creates a
> two-dimensional array.  However, the words created by
> ARRAY don't fetch values from the array or store values
> in the array; they only return the addresses of array
> elements.
> 
> Racket:
> 
> The following function returns a closure:
> 
> (define (array rows cols)
>   (let ((the-vec (make-vector (* rows cols) 0)))
>     (define (calc-index row col) (+ (* row cols) col))
>     (case-lambda
>       [(row col) (vector-ref the-vec (calc-index row col))]
>       [(row col new-val)
>        (vector-set! the-vec (calc-index row col) new-val)])))
> 
> (define board (array 4 4))
> 
> When called with 3 arguments, the third is placed in the array;
> when called with 2 arguments, the value in the cell is returned.
> 
>   > (board 0 0 999)
>   > (board 0 0)
>   999
> 
> (for* ([row 4] [col 4])
>   (board row col (+ col (* row 10))))
> (for ([row 4])
>   (for ([col 4])
>     (display (~a (board row col) #:width 3 #:align 'right)))
>   (newline))
> 
>   0  1  2  3
>  10 11 12 13
>  20 21 22 23
>  30 31 32 33

EMACS Lisp:

(require 'cl)
(defun matrix (rows cols)
  (lexical-let ((cols cols)
                (the-vector (make-vector (* rows cols) 0)))
    (lambda (row col &optional val)
      (let ((i (+ col (* row cols))))
        (if val
          (aset the-vector i val)
          (aref the-vector i))))))

(setq mat (matrix 4 4))

(dotimes (row 4)
  (dotimes (col 4)
    (funcall mat row col (* row col))))

(dotimes (row 4)
  (dotimes (col 4)
    (princ (format "%2d" (funcall mat row col))))
  (terpri))

 0 0 0 0
 0 1 2 3
 0 2 4 6
 0 3 6 9

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Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-09-24 23:09 +0000
  Re: Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-09-24 23:36 +0000
    Re: Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-09-24 23:47 +0000
  Re: Starting Forth 6. "Ed" <invalid@invalid.com> - 2013-09-25 18:22 +1000
    Re: Starting Forth 6. "Elizabeth D. Rather" <erather@forth.com> - 2013-09-25 08:44 -1000
      Re: Starting Forth 6. hughaguilar96@yahoo.com - 2013-09-25 20:09 -0700
        Re: Starting Forth 6. albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-09-26 12:27 +0000
          Re: Starting Forth 6. "Elizabeth D. Rather" <erather@forth.com> - 2013-09-26 09:09 -1000
            Re: Starting Forth 6. hughaguilar96@yahoo.com - 2013-09-27 23:16 -0700
              Re: Starting Forth 6. the_gavino_himself <visphatesjava@gmail.com> - 2013-11-16 17:07 -0800
            Re: Starting Forth 6. "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2013-10-11 22:37 -0700
              Re: Starting Forth 6. the_gavino_himself <visphatesjava@gmail.com> - 2013-11-16 17:11 -0800
                Re: Starting Forth 6. "Stanley Daniel de Liver" <notagoodone@invalid.org.invalid> - 2013-12-11 16:49 +0000
          Re: Starting Forth 6. "Ed" <invalid@invalid.com> - 2013-09-27 11:39 +1000
            Re: Starting Forth 6. "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2013-10-11 22:39 -0700
          Re: Starting Forth 6. hughaguilar96@yahoo.com - 2013-09-30 16:47 -0700
          Re: Starting Forth 6. David Thompson <dave.thompson2@verizon.net> - 2013-10-12 18:22 -0400
            Re: Starting Forth 6. albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-13 12:17 +0000
        Re: Starting Forth 6. Whammo <sidciavic@gmail.com> - 2013-09-26 11:37 -0700
          Re: Starting Forth 6. hughaguilar96@yahoo.com - 2013-09-27 22:28 -0700
          Re: Starting Forth 6. "Clyde W. Phillips Jr." <cwpjr02@gmail.com> - 2013-10-11 22:34 -0700
    Re: Starting Forth 6. hughaguilar96@yahoo.com - 2013-09-25 19:58 -0700
  Re: Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-10-01 15:21 +0000
  Re: Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-10-12 09:17 +0000
  Re: Starting Forth 6. "WJ" <w_a_x_man@yahoo.com> - 2013-10-12 19:01 +0000

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