in reply to Re^3: A "but" operator.
in thread A "but" operator.

Since "A but B" is really a conjunctive inversion, discursively it should be equivalent to "A and not B".

And since "A and not B" is equivalent to "not (if A then B)", or in other words, "not (B if A)", couldn't this be said thusly, to be perly, "B unless A"?

Thoughts?
-v
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Re^5: A "but" operator.
by dragonchild (Archbishop) on Sep 28, 2004 at 12:34 UTC
    This is where predicate logic doesn't work as well as set theory. "A but B" is actually more akin to "A minus B", where A and B are both sets. Or, in Perl, 
    my @A = ( ... );
my @B = ( ... );

my %B = map { $_ => !!1 } @B;

# "A but B"
grep { !$B{$_} } @A;

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    Which is very close to the mixin concept that Perl6 will apply to the term "but".

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