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arraysformatcommon-lisp
rfsbraz
rfsbraz

Reputation: 2111

Lisp Format Procedure Applied to Arrays

I need some help with the format function and arrays.

My objective is to print a 2 dimensional array of N·N integer values as N integers per line. For example:

#2A((1 2 3)
    (4 5 6)
    (7 8 9))

should be printed as

1 2 3 
4 5 6
7 8 9

I couldn't find any documentation on how to use format to print arrays. Can it actually be done, or should I convert my array into a list and use something like:

(format t "~{~%~{~A~^ ~}~}"  list)

Upvotes: 4

Views: 1638

Answers (2)

Andy
Andy

Reputation: 3170

(defun show-board (board)
  (loop for i below (car (array-dimensions board)) do
        (loop for j below (cadr (array-dimensions board)) do
          (let ((cell (aref board i j)))
            (format t "~a " cell)))
        (format t "~%")))

Upvotes: 4

Svante
Svante

Reputation: 51511

If I am not mistaken, there is no direct way for format to go "into" an array. You could write your own function, to be used by tilde-slash (~/function/, see CLHS), or you could coerce the array to a list and use either the directives you proposed, or ~/pprint-tabular/. If you want to define your own, the CLHS has example code for pprint-tabular which you could modify for arrays.

Upvotes: 4

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