Re: Pack in perl6
On 02/14/2011 02:41 AM, Carl Mäsak wrote:
--snip--
to me that a Buf could be output without first having been converted
to a Str. A conversion may or may not be necessary for it to work.
S32/IO says that IO.write will output a Buf.
On Feb 14, 2011, at 12:37 AM, Richard Hainsworth wrote:
--snip--
I am not too clear on how pack works in perl5.
Is there a work around in perl6 to achieve the same result, viz.,
not using pack?
This code works for me on the latest released Rakudo;
use v6;
my @fake =
[ 0, 0, 0, 0, -1, -1, -1, -1, -1, 0, 0, 0, -1, -1,
-1, -1, ], # 0f, 8f
[ -1, 0, -1, 0, -1, 0, -1, 0, 0, 0, -1, 0, -1, 0,
-1, 0, ], # aa, 2a
[ 0, -1, 0, -1, 0, -1, 0, -1, -1, -1, 0, -1, 0,
-1, 0, -1, ], # 55, d5
;
my ( $h, $w ) = ( @fake.elems, @fake[0].elems );
sub dot ( $x, $y ) { return @fake[$x][$y] }
my $fh = open( 'mandelbrot.pbm', :w, :bin );
for ^$h -> $x {
for [^$w].map({ -1 * dot($x, $_) }) {
$fh.write( Buf.new( :2("$^a$^b$^c$^d$^e$^f$^g
$^h"), :size(8) ) );
}
}
$fh.close;
Output:
$ hexdump mandelbrot.pbm
000 0f 8f aa 2a 55 d5
006
Note that 8 implicit params (like $^h) are needed, only
because .batch(8) is not yet implemented.
for [^$w].map({ -1*dot($x, $_) }).batch(8) -> @b { # NYI
$fh.write( Buf.new( :2( @b.join('') ), :size(8) ) );
}
Note also that Buf is specced to work differently than as I used it
here, and so may change in the future.
Buf.new should have a different API, and a Buf with size(1) should (I
think) autopack 8 bits into a byte on output.
--
Hope this helps,
Bruce Gray (Util of PerlMonks)
Re: Pack in perl6
I am not too clear on how pack works in perl5.
Is there a work around in perl6 to achieve the same result, viz., not
using pack?
Richard
On 02/14/2011 02:41 AM, Carl Mäsak wrote:
Richard (>):
I came across the idiom
print "P4\n$w $h\n";
for my $y (0..$h-1) {
print pack 'B*', pack 'C*', map dot($_, $y), 0..$w-1;
}
in a perl5 program for outputting dots in a graphical format. dot() produces
a 0 or -1.
I found the 'pack' function in perl6, but it does not seem to work the same.
Two differences that I can think of:
* The pack function in Rakudo is not fully implemented. For the cases
"B*" and "C*", I can definitely imagine that it doesn't work yet.
Patches are welcome. I also plan to find some time to work more on it
myself.
* The fundamental difference in Perl 6 would be that a call to 'pack'
would result in a Buf, not a string as in Perl 5. (This is because
Perl 6 makes a clear separation between sequences of bits/bytes, and
strings of characters. 'pack' deals in the former.) It's not immediate
to me that a Buf could be output without first having been converted
to a Str. A conversion may or may not be necessary for it to work.
// Carl
Re: Pack in perl6
Richard (>):
> I came across the idiom
>
> print "P4\n$w $h\n";
> for my $y (0..$h-1) {
> print pack 'B*', pack 'C*', map dot($_, $y), 0..$w-1;
> }
>
> in a perl5 program for outputting dots in a graphical format. dot() produces
> a 0 or -1.
>
> I found the 'pack' function in perl6, but it does not seem to work the same.
Two differences that I can think of:
* The pack function in Rakudo is not fully implemented. For the cases
"B*" and "C*", I can definitely imagine that it doesn't work yet.
Patches are welcome. I also plan to find some time to work more on it
myself.
* The fundamental difference in Perl 6 would be that a call to 'pack'
would result in a Buf, not a string as in Perl 5. (This is because
Perl 6 makes a clear separation between sequences of bits/bytes, and
strings of characters. 'pack' deals in the former.) It's not immediate
to me that a Buf could be output without first having been converted
to a Str. A conversion may or may not be necessary for it to work.
// Carl
