Re (tilly) 1: Apocalypse 3

Hmmm...

:=, laziness, he is thinking big. I hope he thinks through the consequences. Otherwise he may just find me submitting a bug report about the following code:

$x := $y + 5;
$y := $x -3;
print "Answer: ($x, $y)\n";
[download]

Unless, of course, it works. In which case I shall probably sacrifice burnt offerings at TheDamian's altar. (And then try to break it with a non-linear system of equations.)

In a similar and more reasonable vein, I hope that his thinking about laziness, :=, and slice mechanics goes far enough that you can readily (for instance) define the Fibonacci sequence as a lazy list and have it work right...

Comment on Re (tilly) 1: Apocalypse 3 Download Code

Replies are listed 'Best First'.
Re: Re (tilly) 1: Apocalypse 3 by TheDamian (Vicar) on Oct 05, 2001 at 12:19 UTC
I'm afraid `:=` isn't the fully fledged unification operator you're hoping for. As I'll explain in Exegesis 3, it's really just an aliasing mechanism. So your declarative emergent `$x` and `$y` values aren't actually being declared, or emerging either. `:-(` In fact, you'd just get `$x` aliased to the (constant) result of `$y+5` (which will be `5` if there's no prior assignment to `$y`), and then `$y` aliased to the (constant) result of `$x-3` (which will be `2` under the previous assumption). However, as a consolation prize for having suggested human sacrifice to me (you did intend it to be a human burnt offering, didn't you???), I have now added a Data::Unification module to my ToDo list. `;-)` Damian	[reply] [d/l] [select]
Re: Re: Re (tilly) 1: Apocalypse 3 by $code or die (Deacon) on Oct 06, 2001 at 07:01 UTC
Hi Damian, In the Section "Applied Laziness 101" of the third Exegesis, you wrote: Of course, if we'd written: my ($name, $vers, $status, $costs, @and_the_rest) = <fh>; The the entire file would have been read Did you mean: my ($name, $vers, $status, $costs, *@and_the_rest) = <fh>; or will array assignment work differently on the diamond operator? Simon Flack ($code or die) `$,=reverse'"ro_';s,$,\$,;s,$,lc ref sub{},e;$, =~y'_"' ';eval"die";print $_,lc substr$@,0,3;`	[reply]
Re: Re: Re: Re (tilly) 1: Apocalypse 3 by TheDamian (Vicar) on Oct 06, 2001 at 10:07 UTC
Did you mean: `my ($name, $vers, $status, $costs, *@and_the_rest) = <fh>;` [download] No. I did mean just what I wrote. Regular `=` assignments have the same "slurp-it-all-up" semantics as in Perl 5. The flattening asterisk is only required in subroutine parameter lists or `:=` bindings.	[reply] [d/l]


Come for the quick hacks, stay for the epiphanies.
	PerlMonks