Re^2: Perl 5 Optimizing Compiler, Part 9: RPerl.org & The Low-Magic Perl Commandments

[tobyink]

Perl without its internal 'magic' implementation is essentially no longer Perl.

Agreed. But I don't think the intention is for these to not work. Merely for a Perl implementation that is able to optimize particular sections of code that don't need magic. (Perhaps using a no magic; pragma as a hint to the compiler of what sections it can optimize.)

That certainly seems a worthy thing to work on.

[Jenda]

The catch is that as soon as that section uses a parameter or a global, it has no chance to know whether there will be any magic!

Does

sub addOne {
  my ($num) = @_;
  return $num + 1;
}

need any magic? No? So what happens if I pass the subroutine a tie()d variable?

I'd like to ask the OP to restrict himself to a recent version of English if he decides to reply. His attempts at old English are funny for two sentences, boring for ten and right away annoying for longer posts.)

[Will_the_Chill]

Hi Jenda,

My only use of old English is The Book Of RPerl, and perhaps to a trivial degree the use of "thou shalt" and "thou shalt not" in The Low-Magic Perl Commandments. Just for you, just in this post, I'll replace "Thou Shalt Not" with "DON'T". :-)

To address your concerns, globals are not allowed and tied variables are not allowed.

LMPC #17. DON'T Use Dynamic-Type Data, Auto-Vivification, Or Tied Variables

LMPC #19. DON'T Use Private Dynamic-Scope (“local”), Private Persistent Lexical-Scope (“state”), Global, Or Package Variables (“our”)

Does that answer your questions?

Thanks,
~ Will

[Jenda]

No it doesn't. The point is that you can't compile a piece of code without magic, because the magic may come from the outside. So even if YOU do follow all those commandments, someone else might not. The result is that even if you do follow all those commandments to the letter, the amount of code that may be safely compiled in a no-magic mode is gonna be fairly small.

[Will_the_Chill]

tobyink,

You are absolutely correct in every regard.

People have been talking about a "no magic;" pragma for years:

one more in support for "no magic" pragma, Anthony Baxter to Tom Christiansen, Tue 04 Mar 1997

You will note, hopefully happily so, this is already codified in The Low-Magic Perl Commandments:

LMPC #12. Thou Shalt Use Pragmata To Mark Magic Level Of Code (“use magic;” & “no magic;”)

Thank you for your moral support! :-)

Perling,
~ Will the Chill