Middle three digits: Difference between revisions
→{{header|Common Lisp}}
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Line 1,966:
=={{header|Common Lisp}}==
===Solution #1===
<syntaxhighlight lang="lisp">
(defun mid3 (n)
Line 2,007 ⟶ 2,008:
-2002: Need odd number of digits, not 4.
0: Zero is 1 digit</pre>
===Solution #2===
<syntaxhighlight lang="lisp">
(defun mid3 (i)
(let ((ch-vec (coerce (format nil "~A" (abs i)) 'vector)))
(when (evenp (length ch-vec))
(return-from mid3
(format nil "Error: The number representation must have an odd ~
number of digits.")))
(when (and (< i 100)
(> i -100))
(return-from mid3
(format nil "Error: Must be >= 100 or <= -100.")))
(let ((half (/ (1- (length ch-vec)) 2)))
(return-from mid3 (format nil "~A~A~A"
(elt ch-vec (1- half))
(elt ch-vec half)
(elt ch-vec (1+ half))))
)))
</syntaxhighlight>
Test code:
<syntaxhighlight lang="lisp">
(defun test-mid3 ()
(let ((test-lst (list 123
12345
1234567
987654321
10001
-10001
-123
-100
100
-12345
1
2
-1
-10
2002
-2002
0
)))
(labels
((run-tests (lst)
(cond ((null lst)
nil)
(t
(format t "~A ~15T ~A~%" (first lst) (mid3 (first lst)))
(run-tests (rest lst))))))
(run-tests test-lst)))
(values)
)
</syntaxhighlight>
{{out}}
<pre>
123 123
12345 234
1234567 345
987654321 654
10001 000
-10001 000
-123 123
-100 100
100 100
-12345 234
1 Error: Must be >= 100 or <= -100.
2 Error: Must be >= 100 or <= -100.
-1 Error: Must be >= 100 or <= -100.
-10 Error: The number representation must have an odd number of digits.
2002 Error: The number representation must have an odd number of digits.
-2002 Error: The number representation must have an odd number of digits.
0 Error: Must be >= 100 or <= -100.
</pre>
=={{header|D}}==
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