Re: Trade-off, option, choice.

On 2005-12-31 17:24:42 +0000, "Carl Taylor" <carltaylor@xxxxxxx> said:

(defun get-char-grid-row (row x-grid)
  (declare (type fixnum row))
  (let ((col-cnt (array-dimension x-grid 1)))
     (map 'string #'identity
       (make-array col-cnt
                            :element-type (array-element-type x-grid)
                            :displaced-to x-grid
                            :displaced-index-offset (* row col-cnt)))))


(defun get-char-grid-col (col x-grid)
  (declare (type fixnum col))
  (map 'string #'identity
     (loop :for i fixnum
               :repeat (the fixnum (array-dimension x-grid 0))
               :collect (aref x-grid i col))))


CL-USER 13 >
(get-char-grid-row 2 #2A((#\a #\b #\c) (#\d #\e #\f) (#\g #\h #\i)))
"ghi"

CL-USER 14 >
(get-char-grid-col 1 #2A((#\a #\b #\c) (#\d #\e #\f) (#\g #\h #\i)))
"beh"


That's very interesting, but you still end-up with two functions,
one for row access and one for column access. That is what I wanted
to parameterize on.

Ideally, I'd have either of

(defun get-grid-string (grid position direction)
 ( ...

with usage:
(get-grid-string #2A((#\a #\b #\c) (#\d #\e #\f) (#\g #\h #\i)) 1 :by-column) 
"beh"

if it turns out that providing the direction (rows vs cols)
explicitely is required,

or

(defun get-grid-straing (grid position)
 ( ...

if the direction can be "coded into" the position itself.

with usage:
(get-grid-string #2A((#\a #\b #\c) (#\d #\e #\f) (#\g #\h #\i)) 
(make-position 2 :by-row))
"ghi"

My point is that I've already got non trivial (working) code
to handle the "rows" case, and I'd rather amend it to deal
with both directions than copy-paste-patch a second instance
of every single row related function into a nearly indentical
column related function.

Many Thanks.
--
JFB

.

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