Formatting a list

Question

I have the following list: (X X O NIL NIL O NIL NIL O)

I'd like to format it to look like this:

X | X | O
--+---+--
  |   | O
--+---+--
  |   | O

I could probably cobble something together with what little I know about Lisp and FORMAT, but it would probably be pretty gross. Any pointers would be greatly appreciated.

Just do it. Worry about fixing the grossness once you have a version that works. — Gareth Rees, Dec 05 '10 at 21:30

jtdubs · Accepted Answer · 2010-12-06T02:43:37.383

6

* (format t "~{~A | ~A | ~A~%~^--+---+--~%~}"
    (mapcar (lambda (x) (or x " ")) '(X O X NIL X X O X NIL)))
X | O | X
--+---+--
  | X | X
--+---+--
O | X |
NIL

edited Dec 06 '10 at 02:43

answered Dec 05 '10 at 21:39

jtdubs

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score 1 · Answer 2 · answered Dec 06 '10 at 09:32

* (format t "~{~A | ~A | ~A~%~^--+---+--~%~}"
    (mapcar (lambda (x) (or x " ")) '(X O X NIL X X O X NIL)))
X | O | X
--+---+--
  | X | X
--+---+--
O | X |
NIL

A little explanation about the format string in the above. Crucial here are the '~{' '~}' and '~^'. A pair of matching Tilde braces take a list as input argument and iterate over it. The ~^ controls an early escape from this loop, if the list being iterated over is empty. Relevant documentation ~{ and ~^.

Formatting a list

2 Answers2

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