use A;
use B;

$A_obj = A->new(16);
$B_obj = B->new(6);

my $n1 = $A_obj - $B_obj; # $n1 is an A object with value 10
my $n2 = $B_obj - $A_obj; # Fatal error
[download]

I have the following Type defined.

package Types;

use v5.34;
use warnings;

use Type::Utils   qw( as coerce declare from via );
use Types::Common qw( Enum Str );
use Type::Library -base, -declare => qw(
    CreditType
    InvoiceType
);

declare InvoiceType, as Enum [qw/
    ACCPAY
    ACCREC
/];

coerce InvoiceType,
    from Str,
    via {
        #warn "Trying to coerce $_\n";
        my %types = (
            Invoice         => 'ACCREC',
            SupplierInvoice => 'ACCPAY',
        );
        #my $ret = $types{$_};
        #warn "Returning $ret\n";
        return $types{$_};
     }
;

declare CreditType, as Enum [qw/
    ACCPAYCREDIT
    ACCRECCREDIT
/];

coerce CreditType,
    from Str,
    via {
        warn "Trying to coerce $_\n";
        my %types = (
            Credit         => 'ACCRECCREDIT',
            SupplierCredit => 'ACCPAYCREDIT',
        );
        my $ret = $types{$_};
        warn "Returning $ret\n";
        return $types{$_};
     }
;

1;
[download]

I have a class that uses the types as a union, this or that

package MyApp;

use v5.34;
use warnings;

use Moo;
use Types qw/ InvoiceType CreditType /;

has 'type' => (
    is       => 'ro',
    isa      => InvoiceType | CreditType,
    required => 1,
    coerce   => 1,
);


sub run {
    my ($self) = @_;

    say "Running with ".$self->type;
}

1;
[download]

I have a test to make sure it's doing what I expect `t/type.t`

#!/opt/perl5/bin/perl

use v5.34;
use warnings;

use Test::More;

use Types qw( InvoiceType CreditType );

{
    subtest 'Type coercion' => sub {
        is InvoiceType->coerce('Invoice'), 'ACCREC',
            'Can coerce a sales invoice';
        is InvoiceType->coerce('SupplierInvoice'), 'ACCPAY',
            'Can coerce a supplier invoice';

        is CreditType->coerce('Credit'), 'ACCRECCREDIT',
            'Can coerce a credit type';
        is CreditType->coerce('SupplierCredit'), 'ACCPAYCREDIT',
            'Can coerce a supplier credit type';
    };
}

{
    my $class = 'MyApp';
    use_ok($class);

    subtest 'Class coercion' => sub {
        for my $t ( qw/Invoice SupplierInvoice Credit SupplierCredit /
+ ) {
            note "Type=$t";
            my $x = new_ok($class => [ type => $t ]);
            note "Now Type=".$x->type;
        }
    };

}

done_testing;
[download]

t/type.t ..
# Subtest: Type coercion
    ok 1 - Can coerce a sales invoice
    ok 2 - Can coerce a supplier invoice
    ok 3 - Can coerce a credit type
    ok 4 - Can coerce a supplier credit type
    1..4
ok 1 - Type coercion
ok 2 - use MyApp;
# Subtest: Class coercion
    # Type=Invoice
    ok 1 - An object of class 'MyApp' isa 'MyApp'
    # Type=SupplierInvoice
    ok 2 - An object of class 'MyApp' isa 'MyApp'
    # Type=Credit
    not ok 3 - MyApp->new() died

    #   Failed test 'MyApp->new() died'
    #   at t/type.t line 31.
    #     Error was:  Undef did not pass type constraint "InvoiceType|
+CreditType" (in $args->{"type"}) at /home/dpaikkos/spl/local/lib/perl
+5/Test/More.pm line 741
    #     "InvoiceType|CreditType" requires that the value pass "Credi
+tType" or "InvoiceType"
    #     Undef did not pass type constraint "InvoiceType"
    #         "InvoiceType" is a subtype of "Enum["ACCPAY","ACCREC"]"
    #         "Enum["ACCPAY","ACCREC"]" requires that the value is def
+ined
    #     Undef did not pass type constraint "CreditType"
[download]

I excel at leaving typos in my code but I am pretty sure there are none in the code so far. The coercions appear to work in a stand alone fashion but when used as a union, the 2nd Type does not appear to apply the coercion. If I swap the "CreditType" to be the first item, I find that the InvoiceType fails.

I suspect I could use some kind of named parameterized coercion and `plus_coercions` but I hit this snag and haven't been able to move forward.

Does anyone have any insights into what I'm doing wrong?

Is it possible to run WebPerl inside a PWA?

Hence effectively running Perl inside an app which can be installed on Android, Win, Linux?

Has it been attempted yet?

What are the results?

Does it reduce the startup time of Perl because it's running hot in the background?

When the program below reaches the start function, it fails with the seemingly nonsensical error "Can't locate auto/Tk/ROText/FILENO.al". Tieing only STDOUT to the same widget is no problem.

Does anyone have any insight as to what is happening here?

use warnings;
use strict;

use IPC::Run qw(start pump finish timeout);
use Tk;
require Tk::ROText;

my $mw = MainWindow->new(-title => "   NON BLOCKING");
my $outw = $mw->Scrolled('ROText',  
            -font => "{Courier New} 10 bold", 
                -background => 'DarkBlue', 
            -foreground => 'OldLace',
            -scrollbars => 'se',
            -wrap => 'none',
            -width => 100,
            -height => 10,
            )->pack(-fill => "both", -expand => 1);
                                                                      
+                                          
# tie *STDOUT, 'Tk::Text', $outw;
tie *STDERR, 'Tk::Text', $outw;

my ($in, $out, $err) = ('', '', '');    
my $h;

if (! defined(eval { $h = start ['cmd.exe', '/c', 'dir'], \$in, \$out,
+ \$err; })) 
{
  print "\nStart failed: $@\n";
}

while($h->pumpable) 
{
  $h->pump;
  print $out;
  $out = '';
}

$h->finish;

MainLoop;
[download]

Just another rant ...

Yesterday, I improved a small helper script that reads an SVG file and converts that to code fragments for drawing lines and texts. (The target does not support displaying and manipulating SVG images the way I need it.) The script was (and still is) too stupid for all SVG features, because it only needs to process one image, supplied by our client.

The first image was years old, all coordinates were absolute. The image was changed, using a different version of the image editor, and suddenly, coordinates were relative. So I had to change the script. Wash, rinse, repeat. Yesterday, the script (and I) learned about horizontal and vertical line shortcuts, and shorcuts for cubic bezier curves. And about the completely INSANE way of representing paths in SVG.

SVG is structured. It's XML after all, so you can group elements, give each element an ID, apply CSS. Great. And all the code you need for that is already implemented. It's just XML.

You want a rectangle, green with a red border?

<rect x="10" y="20" width="42" height="8" stroke="#ff0000" stroke-widt
+h="2" fill="#00ff00" />
[download]

A circle is as easy:

<circle cx="10" cy="20" r="8" stroke="#ff0000" stroke-width="2" fill="
+#00ff00" />
[download]

The same principle also applies for text, elipse, polygon and more.

And then, there is something similar to Logo turtle graphics a.k.a. paths. There is an implicit current point, which is the starting point for the next command, and there are commands: Move to, line to, curve to, close path.

How would you expect to see that in an XML-based vector image format? Like this:

<path x="50" y="50" stroke="#ff0000" stroke-width="2" fill="#00ff00">
    <lineto x="75" y="75" />
    <lineto x="75" y="25" />
    <closepath />
</path>
[download]

XML, like all other elements, testable, parseable by any XML parser?

Dream on! It looks like this:

<path d="M396.73,645.98c-49.05,43.57-88.42,71.92-118.1,85.05-1.85.43-1
+7.07,11.54-45.26-.97-9.7-2.33-78.64-37.77-123.94-89.59,0,0-39.21-47.6
+6-50.48-134.8-7.51-58.09-13.85-106.3-19-144.64-14.55-30.82-24.76-38.5
+3-30.62-23.11-3.7,22.95,16.29,117.5,21.48,128.86"/>
[download]

No, there was no cat running over the num pad. That how SVG represents paths. In a f*ing string looking more like a historic modem command than anything structured.

Yes, there is structure. Upper and lower case letters followed by zero or more numbers. The letters are commands, the numbers are the arguments for the commands. Upper case letters indicate absolute coordinates, lower case letters indicate relative coordinates relative to the end point of the previous command.

"But -1.85.43 does not look like a number" you say? Right! Its not a number, its two numbers, -1.85 and 0.43.

"And why are there commas between some numbers, and no commas between other numbers?" Well, the comma is there if there is no implicit way to tell apart two numbers. It could also be a space. A negative number may simply be appended to another number, as for the reader it must be obvious that a "-" can't be within a number, so it must start a new number. The same rule also allows pasting a number n > 0 and n < 1 to be appended without its leading "0" to a non-integer number. It must be obvious for the reader that a non-integer number can not contain two ".", so the second one must start a second number.

This garbage can be expressed as BNF: https://www.w3.org/TR/SVG11/paths.html#PathDataBNF

To make sense of that number garbage, you basically have to take as much characters as possible that form a number, take that as an argument, and look for the next one. Whitespace and commas may be used to separate numbers.

More nonsense?

There is a "lineto" command (L/l) that expects pairs of numbers (coordinates) as arguments. There is a shortcut for horizontal lines ("H" or "h") that accepts only x coordinates, y is implicit from the end point of the previous command. And there is a shortcut for vertical lines ("V" or "v") that accepts only y coordinates. Both H/h and V/v accept MORE THAN ONE ARGUMENT in case you might want to draw two, three, four or ten succeeding horizontal (or vertical) lines.

The "moveto" command (M/m) expects pairs (PLURAL!) of numbers (coordinates). It moves to the first x-y-position, then switches to "lineto" mode, and all but the first two numbers passed to "moveto" acutally behave as if passed to lineto. "M 1 2 3 4 6 5" is exactly equivalent to "M 1 2 L 3 4 6 5".

Then there is cubic Bézier curves. The commands C/c start at the end of the previous command, and expect groups (PLURAL!) of six numbers, coordinates of two control points and an end point to draw the curve. Each group of six numbers draws one curve. There is also a shortcut command "S/s" that expects groups (PLURAL!) of only four numbers, each group specifying only the second control point and the end point. The first control point is either "the reflection of the second control point on the previous command relative to the current point" (the end point of the previous curve), if the previous command was a cubic Bézier curve command, or the end point of the previous command if the previous command was not a cubic Bézier curve.

SVG also has quadratic Bézier curve commands, Q/q for the full spec, and T/t as shortcut. The same madness.

Note that a command named "E" or "e" would cause problems, because numbers may be given in exponential notation: Is "M0-1.2E3,0" the start of a move command with arguments 0, -1.2E+3, 0 or is it a move command with arguments 0 and -1.2 and an E command with arguments 3 and 0? It must be the former, because numbers must be greedily extracted. So if you want an E command, it needs whitespace in front of the E. "M0-1.2 E3,0" is clearly moveto 0, -1.2 followed by E 3, 0.

The SVG spec fights for single bytes in paths, by omitting sepeators for numbers and by nonsense shortcut commands, all in a format that is horrible bloated and repetitive. And the result makes all XML tools completely unusable for paths. XML just sees a string attribute with no more structure.

WHAT WERE THEY SMOKING?

Alexander