Am 24.01.21 um 06:33 schrieb Junio C Hamano:
> Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> writes:
>
>> NOT(A && B) is Equivalent to (NOT(A) OR NOT(B))
>
> At this level, however, the left one looks much simpler than the
> right one ;-)
>
>
>> if (!opt->ignore_locale && is_utf8_locale() && has_non_ascii(p->pattern) &&
>> - !(!opt->ignore_case && (p->fixed || p->is_fixed)))
>> + (opt->ignore_case || !(p->fixed || p->is_fixed)))
>> options |= PCRE2_UTF;
>
> In the context of this expression, well, I guess the rewritten one
> is probably simpler but can we explain the whole condition in fewer
> than three lines? With or without the rewrite, it still looks too
> complicated to me.
Make the condition
if (!opt->ignore_locale &&
is_utf8_locale() &&
has_non_ascii(p->pattern) &&
(opt->ignore_case ||
(!p->fixed &&
!p->is_fixed)))
{
options |= PCRE2_UTF;
}
With the knowledge of the equivalence
(A => B) <=> (NOT(A) OR B)
(A => B means "if A then B"), the condition makes a lot of sense when
read aloud:
if
NOT ignore locale
AND
is UTF8
AND
has non-ASCII
AND
if
NOT ignore case
then if also
NOT fixed
AND
NOT is fixed
then
...
The codition amounts to extending a series of conjunctions with more
conjuctions IF a condition is satisfied. That's quite sensible.
You have to swap the polarity of the first condition of || in your head,
though, to achieve that meaning. That works with every OR condition, BTW.
-- Hannes
