Having ported 20 Perl 5 CPAN modules to Perl 6 in the last few days, these are some things I noticed:
- Perl 6 is sexy! :)
- Before you start porting a module, make sure you understand the class hierarchy of that module. It helps if you've actually used that module in Perl 5 :)
- Port a module even if it depends on some other (not yet ported) modules -- the dependencies can be ported later on.
- Often, the translation P5 → P6 is quite mechanic:
- $array[idx] →
@array[idx] - a ? b : c →
a ?? b :: c - $self->method(...) →
.method(...) - sub { my ($self, $a, $b) = @_; ... } →
method($a, $b) { ... } - $x =~ s/.../.../g →
$x ~~ s:g/.../.../ - $self->{foo} →
$.foo - $foo = "bar" unless defined $foo →
$foo //= "bar" # (//) and (//=) will be in 5.9, too, IIRC - if($foo eq "a" or $foo eq "b" or $foo eq "c") {...} →
if $foo eq "a"|"b"|"c" {...} - foreach my $foo (@baz) {...} →
for @baz -> $foo {...} - Regular expressions:
- [abc] → <[abc]>
- [^abc] → <-[abc]>
- (?:...) → [...]
- $array[idx] →
- Often, you can remove all that Perl 5 argument parsing and simply substitute it by a nice subroutine|method|whatever signature.
-
# This Perl 5 exporting code... require Exporter; our @ISA = qw< Exporter >; our @EXPORT = qw< foo >; sub foo {...} # ...becomes this in Perl 6: sub foo(...) is export {...}
- return map {.4.} sort {.3.} grep {.2.} map {.1.} →
map {.1.} ==> grep {.2.} ==> sort {.3.} ==> map {.4.} ==> return - Especially Perl 6's translation of Perl 5's getter/setter idiom is cool:
# Perl 5 sub get_foo { my $self = shift; my $ret = $self->{foo}; return lc $ret; # always normalize } sub set_foo { my ($self, $to) = @_; $to =~ s/\s+$//; # strip whitespace at the end $self->{foo} = $to; } # Perl 6: has $:foo; sub foo() is rw { return new Proxy: FETCH => { lc $:foo }, STORE => -> $to is copy { $to ~~ s/\s+$//; $:foo = $to; }; } # And then: say $obj.foo; $obj.foo = "..."; # Notice: Standard assignment syntax! # Assignments should look line assingments, not like method calls - If you trust the user to give correct data to accessors, you can also use:
Alternatively, if you don't trust The Evil Users:has $.foo is rw;
subtype OddInt of Int where { $^n % 2 == 1 } has OddInt $.foo is rw; # And then: $obj.foo = 12; # will die (at compile-time!)
You can find a perhaps more recent version of this document in the Pugs SVN repository.
--Ingo
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Replies are listed 'Best First'. | |
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Re: Mini HowTo: How to port Perl 5 modules to Perl 6
by webfiend (Vicar) on Mar 25, 2005 at 20:55 UTC | |
by iblech (Friar) on Mar 25, 2005 at 21:29 UTC | |
Re: Mini HowTo: How to port Perl 5 modules to Perl 6
by crenz (Priest) on Mar 30, 2005 at 09:08 UTC | |
by mkirank (Chaplain) on Mar 31, 2005 at 08:32 UTC |
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