Re: Disappearing code
On Thu, Jan 09, 2003 at 07:55:20PM -0500, John Siracusa wrote:
Has there been any discussion of how to create code in Perl 6 that's there
under some conditions, but not there under others? I'm thinking of the
spiritual equivalent of #ifdef, only Perlish.
In Perl 5, there were many attempts to use such a feature for debugging and
assertions. What everyone wanted to do was write code like this:
debug(Doing foo with $bar and $baz);
foo($bar, $baz);
I would assume it to be a compiler hint via subroutine attribute.
sub debug ($msg) is off {
print STDERR $msg;
}
some this subroutine is a no-op if a flag is set attribute.
--
Michael G. Schwern [EMAIL PROTECTED]http://www.pobox.com/~schwern/
Perl Quality Assurance [EMAIL PROTECTED] Kwalitee Is Job One
Re: Disappearing code
On Thu, Jan 09, 2003 at 11:15:49PM -0500, John Siracusa wrote:
On 1/9/03 10:10 PM, Michael G Schwern wrote:
I would assume it to be a compiler hint via subroutine attribute.
sub debug ($msg) is off {
print STDERR $msg;
}
some this subroutine is a no-op if a flag is set attribute.
Hm, not quite as convenient as setting a package global (constant)
somewhere. Maybe that same off bit could be set from a distance at
compile time?
That would be the if a flag is set part. Point is, its easily handled
by some sort of subroutine attribute which looks at some flag somewhere.
'off' was a bad name for it.
--
Michael G. Schwern [EMAIL PROTECTED]http://www.pobox.com/~schwern/
Perl Quality Assurance [EMAIL PROTECTED] Kwalitee Is Job One
Re: L2R/R2L syntax (was Re: Everything is an object.)
print sort { ... } ~ mymethod(42) ~ @b;
call sort on what comezouta calling mymethod(42) on what comezouta @b.
I think. Indirect objects are still somewhat confusing. :)
If I'm reading the info right on ~, then we want to make it clear
that you _don't_ put it between print and stuff you want to print, or
in other words that this ain't cout.
If I read the conversations right, I think that line is trying to do:
print (to stream mymethod(@b,42)) sort { ... }
I think to make it work like you wanted, you need ()'s
print (sort { ... } ~ mymethod(42) ~ @b); so that the ~ is directly
associated with the sort; otherwise sort is a param to the print, and
we're comezouta'ing the where do i print sort
and sort takes the how do i sort first and the What do i sort
second, yes? which makes me now wonder about all the sort { ... } ~
examples, and my understanding of the whole where do ~ and ~ stick
things? thing ...
OK, looking back, ~ binds to the indirect object ... and Damian's
examples use map { ... } and grep { ... } with ~'s, so I guess the
indirect object would work the same for sort { ... }, but now I'm not real
sure on what the indirect object IS in all these calls ...
Could someone explain how to know what's the indirect object? (who knew
the sentence diagramming would be USEFUL!!)
--attriel
Re: Disappearing code
On 1/9/03 11:27 PM, Michael G Schwern wrote:
On Thu, Jan 09, 2003 at 11:15:49PM -0500, John Siracusa wrote:
On 1/9/03 10:10 PM, Michael G Schwern wrote:
I would assume it to be a compiler hint via subroutine attribute.
sub debug ($msg) is off {
print STDERR $msg;
}
some this subroutine is a no-op if a flag is set attribute.
Hm, not quite as convenient as setting a package global (constant)
somewhere. Maybe that same off bit could be set from a distance at
compile time?
That would be the if a flag is set part. Point is, its easily handled
by some sort of subroutine attribute which looks at some flag somewhere.
Well, er, don't we need to decide what the subroutine attribute is, so that
the compiler will know to honor it and make the code disappear? It
doesn't seem like a feature that can be added from userland after the fact
(but maybe I'm wrong...)
-John
Re: Disappearing code
John Siracusa [EMAIL PROTECTED] wrote: Well, er, don't we need to decide what the subroutine attribute is, so that the compiler will know to honor it and make the code disappear? It doesn't seem like a feature that can be added from userland after the fact (but maybe I'm wrong...) In Perl 5 that could be done from userland, as you say, by using an optree manipulator (optimizer.pm for example). This could even be lexically scoped. [Once the compiler hints are fixed.] I expect Perl 6 to ship with (Parrot::* ?) modules that allow to examine and to modify the compiled form of the programs. Something that probably Java 6 will not have...
Re: Variable Types Vs Value Types
attriel wrote: AssignmentOK?Because... ======== my Basket $c = $a no $c's type: Basket (of Object) X ^ | | $a's type: Set of Apple my Basket of Apple $c = $aok $c's type: Basket of Apple ^ ^ | | $a's type: Basket of Apple Now, just to be sure I didn't miss a step: That second entry is wrong, sin't it? it should be OK? no b/c: C's Type : Basket of Apple X^ || A's Type : Set of Apple yes? Quite correct. I messed up A's type. :-( Could the Secret Maintainers of Perl 6 Truth please update that for the records. Thanks, Damian
Re: L2R/R2L syntax (was Re: Everything is an object.)
Andy Wardley wrote: s/~=/=~/ Indeed. And that's precisely why we're changing it to ~~ in Perl 6. ;-) The first 3 all relate to the familiar concept of 'minus', or more precisely a delta between two values. The last uses '-' as 'dash', another familiar concept which doesn't grate against the first usage, IMHO. Just as ~ and ~ use ~ as a squiggly dash, which doesn't grate either, IMHO. The arrow is a special case. I don't read that first character as '-', I think of the operator as one. I guess the visual cue forces me to see it like that. I'm suggesting that ~ and ~ will be the same. I'm just suggesting the same for the ~ character: This is where I get lost. I see 4 different concepts being overloaded onto '~'. I'd suggest that that's simply because your brain hasn't yet chunked the various uses of the ~ character in these four multicharacter symbols, the way it already has with the - character. So you read the ~'s as symbols rather than characters within symbols, which leads to the matchy or stringy overtones of their appearance to you. But once that chunking does occur for you -- and I'm suggesting it would -- then ~ and ~ will become atomic symbols in your brain, and I think the issue will disappear. Nevertheless, I deeply respect your concerns and your opinions, and appreciate that you look the time to set them out so clearly. So, we're going to have to agree to differ, I suspect. Having presented our respective arguments cogently in this forum, we can happily sit back and let Larry shoulder the burden of deciding this. Thanks, Andy. Damian
Re: L2R/R2L syntax (was Re: Everything is an object.)
Mr. Nobody wrote: I find the normal function call and assignment far more readable than using some weird ugly operator. and later: That's going to be just plain confusing. Arguments to functions are supposed to be on the right. And what's up with using them for assignment? That's making them even more overcomplicated and ugly. Do you care about readability at all? You know, I usually find this kind of unsupported, emotive, ad hominen attack utterly unconvincing. But in this case, I find that your novel approach to our collaborative discussion *has* convinced me of something. *PLONK* Damian
Re: Variable Types Vs Value Types
Damian Conway [EMAIL PROTECTED] writes: attriel wrote: AssignmentOK?Because... ======== my Basket $c = $a no $c's type: Basket (of Object) X ^ | | $a's type: Set of Apple my Basket of Apple $c = $aok $c's type: Basket of Apple ^ ^ | | $a's type: Basket of Apple Now, just to be sure I didn't miss a step: That second entry is wrong, sin't it? it should be OK? no b/c: C's Type : Basket of Apple X^ || A's Type : Set of Apple yes? Quite correct. I messed up A's type. :-( Could the Secret Maintainers of Perl 6 Truth please update that for the records. If you want me to doctor the summary you're going to have to do better than a simple 'please' mate. I want personal tuition on making presentation software actually *enhance* the presentation...
Re: L2R/R2L syntax (was Re: Everything is an object.)
--- attriel [EMAIL PROTECTED] wrote: Could someone explain how to know what's the indirect object? (who knew the sentence diagramming would be USEFUL!!) Short version: If there's two people in the sentence, the verb-ee is either the direct or indirect object. If there's two people and a thing, the -ee is indirect. I hit him. (He's the direct object.) I gave the ball to him. (Ind.) In reality, the reference to indirect object is a bogus equivalence, because we're really making the SUBJECT of the sentence, as hit him :I becomes I.hit(him) However, the original term was a reference to Using an OBJECT's method INDIRECTly, hence indirect object notation. Just to make things less simple. =Austin
Re: Disappearing code
On Thu, 09 Jan 2003 19:55:20 -0500 John Siracusa [EMAIL PROTECTED] wrote: Has there been any discussion of how to create code in Perl 6 that's there under some conditions, but not there under others? I'm thinking of the spiritual equivalent of #ifdef, only Perlish. If the perl6 command-line options are anything like perl5 then you can just use the -P switch if preprocessor commands are your thing. In Perl 5, there were many attempts to use such a feature for debugging and assertions. There has also been a proposal for patching perl5 to add assertions which was recently discussed[1] on p5p, which if accepted has implications for assertions in perl6 surely. Dan [1] http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-11/msg00325.html
Re: L2R/R2L syntax (was Re: Everything is an object.)
Damian Conway said: Andy Wardley wrote: The arrow is a special case. I don't read that first character as '-', I think of the operator as one. I guess the visual cue forces me to see it like that. I'm suggesting that ~ and ~ will be the same. I think that in part this may depend on the font being used. When I first saw these symbols, via webmail on a browser, the tilde appeared half way down the character, in the same position as the dash. This made it obvious to me that it was an arrow of some sort, and it looked good. When I later saw it using mutt in an xterm, the tilde was at the top of the character, where I was more used to seeing it and it didn't look like an arrow any more, nor did it look very good to me. This is the way it looks on my browser ~ When I get home I'll mail a message showing how it looks in my xterm ;-) -- Paul Johnson - [EMAIL PROTECTED] http://www.pjcj.net
Re: Disappearing code
On 1/10/03 11:11 AM, Dan Brook wrote: On Thu, 09 Jan 2003 19:55:20 -0500 John Siracusa [EMAIL PROTECTED] wrote: Has there been any discussion of how to create code in Perl 6 that's there under some conditions, but not there under others? I'm thinking of the spiritual equivalent of #ifdef, only Perlish. If the perl6 command-line options are anything like perl5 then you can just use the -P switch if preprocessor commands are your thing. Source filtering is not exactly the solution I'm looking for... :) -John
~ and ~ become | and | (was L2R/R2L syntax )
Damian Conway wrote:
Can I suggest that an alternative solution might be the following:
So an L2R array-processing chain is:
@out = @a ~ grep {...} ~ map {...} ~ sort;
There might also be a be special rule that, if the RHS is
a variable, the LHS is simply assigned to it. Allowing:
@a ~ grep {...} ~ map {...} ~ sort ~ @a;
Further suppose that ~ takes its right argument, and binds
it in the indirect object slot of the left argument, which
argument it then calls. So an R2L array-processing chain is:
@out = sort ~ map {...} ~ grep {...} ~ @a;
Or, under a special rule for variables on the LHS:
@out ~ sort ~ map {...} ~ grep {...} ~ @a;
That way, everything is still a method call, the ultra-low precedence of
~ and ~ eliminate the need for parens, and (best of all) the
expressions
actually *look* like processing sequences.
Damian
my knee-jerk reaction,
| is evocative of pipelines in bash, etc...
| is somewhat less evocative, but related to (cat *) as a
sub-process (in csh ??)
yours feels slightly less noisy, but also less familiar/mnemonic.
Re: Array Questions
On Thursday, January 9, 2003, at 03:24 AM, Damian Conway wrote:
Michael Lazzaro asked:
class FileBasedHash is Hash { ...stuff... };
my %data is FileBasedHash('/tmp/foo.txt');
Yes.
my $path = '/tmp/foo.txt';
my %data is FileBasedHash($path);
Indeed
Great -- then I have only one more question, I think. In the words of
a certain cartoon character, what's *this* button do?
my $b is $a;
My presumption:
1) If Cmy $a = MyScalar, e.g. $a is set to a class name, it's saying
that $b is implemented by a MyScalar. But I don't know if these two
lines would really have the same result, given rule (2), below:
$a = MyScalar;
$a = 'MyScalar';
2) If Cmy $a = $fooObj, e.g. it's set to an arbitrary object
instance, it's saying that $b is implemented by the object instance in
$a. So these statements are equiv:
my $a = FileBasedHash.new($path);
my %b is $a;
vs.
my %b is FileBasedHash($path);
If the object in $a doesn't implement the Scalar interface, it's a
runtime error. And note that Cmy %b is %a would be a runtime error,
one would hope.
MikeL
(My original gut desire was that Cmy $b is $a be the ultracool perl6
way of achieving prototype-based (classless) OO, such that $b inherits
its base functionality from $a. As inherently cool as that is, I don't
think that can possibly work, and it would conflict *severely* with
these other meanings. Ah, well.)
Re: Array Questions
On Fri, Jan 10, 2003 at 10:28:49AM -0800, Michael Lazzaro wrote: Great -- then I have only one more question, I think. In the words of a certain cartoon character, what's *this* button do? my $b is $a; And no matter what that button does, will this: my $a $b; be illegal? -Scott -- Jonathan Scott Duff [EMAIL PROTECTED]
Re: L2R/R2L syntax (was Re: Everything is an object.)
On Friday 10 January 2003 11:42 am, Paul Johnson wrote: Damian Conway said: Andy Wardley wrote: The arrow is a special case. I don't read that first character as '-', I think of the operator as one. I guess the visual cue forces me to see it like that. I'm suggesting that ~ and ~ will be the same. I think that in part this may depend on the font being used. True. It looks horrid in misc-fixed-* (what I'm assuming Paul has in his xterm).
RE: L2R/R2L syntax (was Re: Everything is an object.)
Paul Johnson [EMAIL PROTECTED] wrote: When I later saw it using mutt in an xterm, the tilde was at the top of the character, where I was more used to seeing it and it didn't look like an arrow any more, nor did it look very good to me. Well, at least now I understand why some people didn't see the squiggly arrow immediately, as I did. It seemed so obvious to MY eyes, I couldn't understand what the big deal was. I have been (quietly) siding with the let's use unicode characters as operators camp. But this little brouhaha has me splitting into two universes: Universe 1 (anti-unicode): If we have this much trouble seeing a tilde the same way, what are the chances that all these cool new operators will be visually comparable to all P6 coders? Universe 2 (pro-unicode): If we had a Unicode 'squiggly arrow' operator, then however it looks on everybody's display, it ought to at least look like some kind of squiggly arrow. We'll say goodbye now. =thom Delusions are often functional. A mother's opinions about her children's beauty, intelligence, goodness et cetera ad nauseam, keep her from drowning them at birth. --Lazarus Long
RE: L2R/R2L syntax (was Re: Everything is an object.)
Andrew Rodland [EMAIL PROTECTED] wrote: But you're missing the most important part! I propose that these operators should be named gozinta ( ~) and comezouta ( ~ ), just so that we can say that perl has them. Not to mention that the names work pretty well, for me. Here, here! All in favor, say Aye! 'Course, then I've gotta explain why $x = 7 ~ 63; doesn't evaluate to 9 :-) =thom Be wary of strong drink. It can make you shoot at tax collectors...and miss. --Lazarus Long
Re: L2R/R2L syntax (was Re: Everything is an object.)
Date: Fri, 10 Jan 2003 08:12:48 -0800 (PST) From: Austin Hastings [EMAIL PROTECTED] --- attriel [EMAIL PROTECTED] wrote: Could someone explain how to know what's the indirect object? (who knew the sentence diagramming would be USEFUL!!) Short version: If there's two people in the sentence, the verb-ee is either the direct or indirect object. If there's two people and a thing, the -ee is indirect. I hit him. (He's the direct object.) I gave the ball to him. (Ind.) In reality, the reference to indirect object is a bogus equivalence, because we're really making the SUBJECT of the sentence, as And the one we're modeling it after in Perl is: I gave him the ball. In Perl 6: gave him: the ball; But a better sentence to use as an example here would be a command, as most imperative (computer) languages use: Give the ball to him. Or equivalently, Give him the ball. In Perl 6: give him: the ball; And as you can see, it is no longer a misnomer. The subject is implicitly you or (in a Star Trek sense) computer. hit him :I becomes I.hit(him) I don't think so. Rather, that becomes: him.hit(I); And to clarify, you should probably format it like this: hit him: I; But computer languages aren't generally used to specify past tense anyway To summarize, the indirect object goes Ibetween the verb and the direct object, before the colon. Luke
Re: Array Questions
From: Thom Boyer [EMAIL PROTECTED]
Date: Fri, 10 Jan 2003 13:57:26 -0700
From: Michael Lazzaro [mailto:[EMAIL PROTECTED]]
But I don't know if these two
lines would really have the same result, ...
$a = MyScalar;
$a = 'MyScalar';
Hrmm. Didn't Larry decree that there are no bare words, but that a class
name will evaluate to the string representing the spelling of the class
name? In otherwords, aren't those two assignments identical by definition?
You're correct in that there are no barewords. But, IIRC, a class
name doesn't just evaluate to a string representing the spelling of
the class name. Classes are first-class objects in Perl 6, just as
subroutines were in Perl 5.
The two variables would only behave the same in certain situations
because of symbolic dereferencing. But, they couldn't go by name,
because then what would $foo be here:
$foo = class { has $.bar is public };
As far as the example:
$a = MyScalar;
$b = $a is $a;
(Or something like that) I would imagine that would only work if $a
was known at compile time:
BEGIN { $a = MyScalar; }
$b = $a is $a;
Maybe. Actually, that's quite a difficult question; is MyScalar a
property or a behavior class? Is there a difference, or is the latter
a subset of the former?
But, AFAIK, the two statements are not equivalent.
Luke
Re: L2R/R2L syntax (was Re: Everything is an object.)
Paul Johnson wrote: When I later saw it using mutt in an xterm, the tilde was at the top of the character, where I was more used to seeing it and it didn't look like an arrow any more, nor did it look very good to me. Ah yes, that's the problem. On all my fonts, the tilde appears at the top and it doesn't look anything like an arrow. Viewing it on a web browser with the tilde centered vertically does indeed bring out the arrow-ness of it. A
Re: L2R/R2L syntax (was Re: Everything is an object.)
I don't know about *your* font, but in mine the ~ and ~ versions are
at least twice as readable as the | and | ones.
Just out of curiosity, how did you measure that? ;-)
Well, obviously, I used the Symbol::Readability module:
module Symbol::Readability;
sub delta_r(Str $a, Str $a) returns Int is exported {
return sum [»ord«split/null/,$x] »-« [»ord«split/null/,$y]
}
and then:
#! /usr/bin/perl6
use Symbol::Readability;
print delta_r('~','|');
How else?
;-)
Damian
