Re: Help with Perl 6 script

[Andy Bach]

Yes, Perl 5 and Perl 6 are quite different in many ways.  Some suggested that 
Perl 6 be looked at as not the next iteration of Perl but a new language that 
can be made backward compatible with Perl 5 (there are switches etc that let 
you run P5 code unchanged) but it is not the case of P5 being able to run P6 
code.  You'll have to translate what the p6 code is doing into valid syntax for 
p5.  Or find p6 for windows.  There is a lot of p6 info out there, but not so 
much on the Perl for Beginners list. See:
 https://docs.perl6.org/<https://docs.perl6.org/language/quoting>

and there is the p6 users list
perl6-us...@perl.org

at:
https://lists.perl.org/all.html#p

________________________________
From: Rui Fernandes <rui.kep...@gmail.com>
Sent: Thursday, August 8, 2019 3:07 PM
To: Perl Beginners <beginners@perl.org>
Subject: Help with Perl 6 script

Greetings

I have this Perl 6 script from Rosetta, which I wanted to run on Perl 5 (due to 
the Active Sate Perl and App version that I have). However, several syntax 
errors appear given the difference (some) in language.Here's the script:

---


# Simple Vector implementation
multi infix:<+>(@a, @b) { @a Z+ @b }
multi infix:<->(@a, @b) { @a Z- @b }
multi infix:<*>($r, @a) { $r X* @a }
multi infix:</>(@a, $r) { @a X/ $r }
sub norm { sqrt [+] @_ X** 2 }

# Runge-Kutta stuff
sub runge-kutta(&yp) {
    return -> \t, \y, \δt {
        my $a = δt * yp( t, y );
        my $b = δt * yp( t + δt/2, y + $a/2 );
        my $c = δt * yp( t + δt/2, y + $b/2 );
        my $d = δt * yp( t + δt, y + $c );
        ($a + 2*($b + $c) + $d) / 6;
    }
}

# gravitational constant
constant G = 6.674e-11;
# astronomical unit
constant au = 150e9;

# time constants in seconds
constant year = 365.25*24*60*60;
constant month = 21*24*60*60;

# masses in kg
constant $ma = 2e30;     # Sun
constant $mb = 6e24;     # Earth
constant $mc = 7.34e22;  # Moon

my &dABC = runge-kutta my &f = sub ( $t, @ABC ) {
    my @a = @ABC[0..2];
    my @b = @ABC[3..5];
    my @c = @ABC[6..8];

    my $ab = norm(@a - @b);
    my $ac = norm(@a - @c);
    my $bc = norm(@b - @c);

    return [
        flat
        @ABC[@(9..17)],
        map G * *,
        $mb/$ab**3 * (@b - @a) + $mc/$ac**3 * (@c - @a),
        $ma/$ab**3 * (@a - @b) + $mc/$bc**3 * (@c - @b),
        $ma/$ac**3 * (@a - @c) + $mb/$bc**3 * (@b - @c);
    ];
}

loop (
    my ($t, @ABC) = 0,
        0, 0, 0,                                 # Sun position
        au, 0, 0,                                # Earth position
        0.998*au, 0, 0,                          # Moon position
        0, 0, 0,                                 # Sun speed
        0, 2*pi*au/year, 0,                      # Earth speed
        0, 2*pi*(au/year + 0.002*au/month), 0    # Moon speed
    ;
    $t < .2;
    ($t, @ABC) »+=« (.01, dABC($t, @ABC, .01))
) {
    printf "t = %.02f : %s\n", $t, @ABC.fmt("%+.3e");
}

---

I'm having problem specially in the "multi infix" and even in the "norm" sub 
routine. The problem is that I do not understand the construction of these in 
Perl 5 (otherwise, I would translate this easely, and I wouldn't be asking for 
help...)

Any help is apreciated.

Clear skies

Rui Fernandes