On 2020-01-18 06:09, Tobias Boege wrote:
On Fri, 17 Jan 2020, ToddAndMargo via perl6-users wrote:
Hi All,
https://docs.raku.org/routine/+$CIRCUMFLEX_ACCENT
(Operators) infix +^ยง
multi sub infix:<+^>($a, $b --> Int:D)
Integer bitwise XOR operator: Coerces both arguments to Int and does a
bitwise XOR (exclusive OR) operation.
$ p6 'my uint8 $x=0b0101_0111; my uint8 $y = 0b0000_1111; my uint8 $z =
+^($x, $y ); say "0", $x.base(2); say "0000", $y.base(2); say $z.base(2);'
01010111
00001111
11111101
XOR
A B A xor B
0 0 0
1 0 1
0 1 1
1 1 0
That s not what I am seeing above.
What am I doing wrong this time?
And who set the high bit making $z negative?
As was already mentioned, if you want to use the &infix:<+^> operator,
you have to either call it by its full name as a sub:
&infix:<+^>($x, $y)
or you have to use it according to its syntax category, as an infix:
$x +^ $y
When you write +^($x,$y), its cousin &prefix:<+^> is called instead,
because now you use +^ as a prefix operator. That one performs bitwise
negation on its argument coerced to Int, and since you pass it a list
of length two, you actually evaluate +^2. And that's how you get the
high bit and a value of -3.
Regards,
Tobias
Hi Tobias,
This works perfectly using the syntax $a = $b +^ $c
p6 'my uint8 $x=0b0101_0111; my uint8 $y = 0b0000_1111; my uint8 $z = $x
+^ $y; say "0", $x.base(2); say "0000", $y.base(2); say "0",$z.base(2);'
01010111 # $x
00001111 # $y
01011000 # z = x xor y
But what is now confusing me is $c = +^( $a, $b )
p6 'my uint8 $x=0b0101_0111; my uint8 $y = 0b0000_1111; my uint8 $z =
+^($x, $y); say "0", $x.base(2); say "0000", $y.base(2); say $z.base(2);'
01010111 # $x
00001111 # $y
11111101 # z is not x xor y
Which is clearly not correct. The manual states:
Integer bitwise XOR operator: Coerces both
arguments to Int and does a bitwise XOR
(exclusive OR) operation.
In my example run line, I purposefully left the
high bit off to keep overly helpful Raku from thinking
I had a negative number when it annoyingly overrules
my choice of native type. (Ordinarily I like this
feature, except when doing bitwise operations, I
wish I could turn it off.)
So I am confused.
-T
