Ethan Furman <et...@stoneleaf.us>:
> I would love to see good functional examples as it is definitely a
> weak spot for me.
Oh, if you want to go functional, you should look at idiomatic Scheme
code:
========================================================================
(define (common-prefix-length bytes-a bytes-b)
(let loop ((list-a (string->list bytes-a))
(list-b (string->list bytes-b))
(common-length 0))
(cond
((null? list-a) common-length)
((null? list-b) common-length)
((= (car list-a) (car list-b))
(loop (cdr list-a) (cdr list-b) (+ common-length 8)))
(else
(+ common-length
(vector-ref bit-match
(- 8 (integer-length (logxor (car list-a)
(car list-b))))))))))
========================================================================
Or, translated into (non-idiomatic) Python code:
========================================================================
def common_prefix_length(bytes_a, bytes_b):
def loop(list_a, list_b, common_length):
if not list_a:
return common_length
if not list_b:
return common_length
if list_a[0] == list_b[0]:
return loop(list_a[1:], list_b[1:], common_length + 8)
return common_length + \
bit_match[8 - integer_length(list_a[0] ^ list_b[0])]
return loop(bytes_a, bytes_b, 0)
========================================================================
Marko
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