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.




using Printf
 
function middle3(n::Integer)
    l = ndigits(n)
    iseven(l) && error("n must have an odd number of digits")
    l < 3 && error("n must have 3 digits or more")
    mid = (l + 1) ÷ 2
    abs(n) ÷ 10^(mid-2) % 10^3
end
 
for n = [123, 12345, 1234567, 987654321, 10001, -10001, -123,
         -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0]
    @printf("%10d -> %s\n", n, try middle3(n) catch e e.msg end)
end