mismatch
builtin-function
(mismatch seq1 seq2)
(mismatch test seq1 seq2)
Returns the position of the first mismatch of two sequences. Returns null if
the sequences match.
The default equality test is =.
make-html > (mismatch '(1 2 3 4) '(1 2 3 4))
it: null
make-html > (mismatch '(1 2 3 4) '(1 2 x 4))
it: 2