Task

Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.

Note: The order of the middle digits should be preserved.

Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:

123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345
1, 2, -1, -10, 2002, -2002, 0

Show your output on this page.




middleDigits := proc(n)
	local nList, start;
	nList := [seq(parse(i), i in convert (abs(n), string))];
	if numelems(nList) < 3 then
		printf ("%9a: Error: Not enough digits.", n);
	elif numelems(nList) mod 2 = 0 then
		printf ("%9a: Error: Even number of digits.", n);
	else
		start := (numelems(nList)-1)/2;
		printf("%9a: %a%a%a", n, op(nList[start..start+2]));
	end if;
end proc:
 
a := [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345,
	 1, 2, -1, -10, 2002, -2002, 0]:
for i in a do
	middleDigits(i);
	printf("\n");
end do;