Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
This is increasingly less relevant to Haskell, except of course to demonstrate what a nice language Haskell is. On 20 Jun 2008, at 11:34 pm, Jules Bean wrote: I think where I differ on you is how to map the semantics of a C- like language to explicit references. I would argue that the glyph c in a C-like language denotes the value of C, not the reference to it. C-like languages have, for the most part, value semantics, and call-by-value. The exception of course is what C-like languages called lvalues, but lvalues are only really on the left of the = sign and a few other special positions. I think that's the exception and not the rule. No, this is back to front. C basically follows the Algol 68 idea that the lvalue is the normative thing, and that there is an IMPLICIT COERCION from a variable to its value in certain contexts. C is full of implicit coercions: perhaps the most famous is the one that says that in almost all contexts an array is quietly coerced to a pointer to its first element. The key observation is that an implicit coercion from a variable to its contents is possible, whereas an implicit coercion from a value to the variable that holds it is not. Only the a variable really stands for its address view is coherent. In C, of course, if you want to capture the reference you do it explicitly with c. If we can use evidence from a relative to probe such questions, the fact that you *don't* need an explicit in C++ (when you find a 'reference' to a variable, you use c, not c) strongly suggests that the variable stands for location view is the more useful one. Thankfully, Haskell saves us these perplexities. (And replaces them with other perplexities...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Derek Elkins wrote:
Lambda abstractions should close over bindings. Full stop.
Interesting. I agree with your analysis. I don't think I agree with your
conclusion.
The first surprising behaviour is the correct one. The latter would
be broken.
In my opinion, the reason this behaviour is surprising isn't
mutability, but -implicit- mutability. Let's make bindings immutable,
but add ML-style references to your example.
char ref c = ref(undefined);
while(!eof(fp)) {
c := getChar(fp);
bind_event( ... print !c; ... );
}
compare this to
while(!eof(fp)) {
char c = getChar(fp);
bind_event( ... print c; ...);
}
or
while(!eof(fp)) {
char ref c = ref(getChar(fp));
bind_event( ... print !c; ...);
}
Each of these examples makes it clearer what is going on.
Agreed.
I think where I differ on you is how to map the semantics of a C-like
language to explicit references.
I would argue that the glyph c in a C-like language denotes the value
of C, not the reference to it. C-like languages have, for the most part,
value semantics, and call-by-value.
The exception of course is what C-like languages called lvalues, but
lvalues are only really on the left of the = sign and a few other
special positions. I think that's the exception and not the rule. I
think the rule is that c denotes the value of c, and that's why I
expect a closure to capture the value, not the reference.
In C, of course, if you want to capture the reference you do it
explicitly with c.
Jules
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Richard A. O'Keefe wrote: - what you get is a reference to a variable (as you do in Scheme) but loop variables really are variables, not names for values, so lambdas created in different iterations of the same loop point so the same loop variable, and do not remember the value it had when they were created. The proposal explains how to work around this. This one trips everyone up in Javascript. I think I'm of the opinion that variable capture from lambda formation should always be by value. However you can certainly make an argument that that's inconsistent in a language which generally has mutation/reference semantics. Whichever choice you make, though, document it loudly I predict it will be a source of confusion. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 19 Jun 2008, at 5:53 pm, Jules Bean wrote: Richard A. O'Keefe wrote: - what you get is a reference to a variable (as you do in Scheme) but loop variables really are variables, not names for values, so lambdas created in different iterations of the same loop point so the same loop variable, and do not remember the value it had when they were created. The proposal explains how to work around this. This one trips everyone up in Javascript. What's going on here is a nasty interaction with the semantics of loops. In Smalltalk and Scheme (to name two languages with closures and mutable variables), each iteration of a loop in principle creates a new variable binding. Scheme example: (do ((i 0 (+ i 1)) (l '() (cons (lambda (x) (* x i)) l))) ((= i 10) l)) is equivalent to let f i l = if i = 10 then l else f (i + 1) ((\x - x * i) : l) in f 0 [] except for i and l being potentially mutable in Scheme but not Haskell. The Smalltalk equivalent would be (0 to: 9) collect: [:i | [:x | x*i]] in which (a) each iteration creates a *new* i, and (b) method and block parameters are *not* mutable, because they never are in Smalltalk. Importing only values into closures would not work for Smalltalk. Consider the usual implementation of Smalltalk's equivalent of 'fold: Collection inject: initial into: function |r| r := initial. self do: [:each | r := function value: r value: each]. ^r The mutablity of r here really isn't a problem. Nor is the mutability of variables _as such_ really the problem in the PHP proposal. The problem is that it's the *same* variable every time. If PHP loops introduced new bindings on every iteration, this particular problem would not exist. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Richard A. O'Keefe wrote:
The mutablity of r here really isn't a problem. Nor is the mutability
of variables _as such_ really the problem in the PHP proposal.
The problem is that it's the *same* variable every time. If PHP
loops introduced new bindings on every iteration, this particular
problem would not exist.
Well, arguably it's not only the loop variable that can be susceptible
to this problem. There could be other variables in the loop body which
change each time through (e.g. while loops). Consider this pseudo-code
(sorry, my PHP is a bit rusty, this syntax is C really)
char c;
while (!eof(fp)) {
c = getChar(fp);
bind_event(... some lambda expression referencing c ...);
}
It's pretty surprising to the programmer if all that family of lambda
expressions reference the *variable* c (and hence, in practice, its
final value) rather than the *value* c.
Well, maybe that doesn't surprise everyone. It surprised me the first
time I used closures in Javascript and judging by a few google searches
I wasn't alone in that.
Jules
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Thu, 2008-06-19 at 07:25 +0100, Jules Bean wrote:
Richard A. O'Keefe wrote:
The mutablity of r here really isn't a problem. Nor is the mutability
of variables _as such_ really the problem in the PHP proposal.
The problem is that it's the *same* variable every time. If PHP
loops introduced new bindings on every iteration, this particular
problem would not exist.
Well, arguably it's not only the loop variable that can be susceptible
to this problem. There could be other variables in the loop body which
change each time through (e.g. while loops). Consider this pseudo-code
(sorry, my PHP is a bit rusty, this syntax is C really)
char c;
while (!eof(fp)) {
c = getChar(fp);
bind_event(... some lambda expression referencing c ...);
}
It's pretty surprising to the programmer if all that family of lambda
expressions reference the *variable* c (and hence, in practice, its
final value) rather than the *value* c.
Well, maybe that doesn't surprise everyone. It surprised me the first
time I used closures in Javascript and judging by a few google searches
I wasn't alone in that.
Lambda abstractions should close over bindings. Full stop.
The first surprising behaviour is the correct one. The latter would
be broken.
In my opinion, the reason this behaviour is surprising isn't
mutability, but -implicit- mutability. Let's make bindings immutable,
but add ML-style references to your example.
char ref c = ref(undefined);
while(!eof(fp)) {
c := getChar(fp);
bind_event( ... print !c; ... );
}
compare this to
while(!eof(fp)) {
char c = getChar(fp);
bind_event( ... print c; ...);
}
or
while(!eof(fp)) {
char ref c = ref(getChar(fp));
bind_event( ... print !c; ...);
}
Each of these examples makes it clearer what is going on. Admittedly,
if we write a 'foreachChar' HOF, the difference between the first
implementation and the last will not be apparent from the type. That's
just the nature of the beast; there is simply more than one
implementation.
At any rate, as Richard O'Keefe stated, it's not the lambda's behaviour
that needs to be documented, it's the loop's (or HOFs in general), for
the iteration variables. The ones you introduce are your own concern;
say what you mean.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wednesday 18 June 2008, Luke Palmer wrote:
I don't know that much PHP, but I find the lexical keyword to be a
nuisance. What are the semantics if the lexical keyword is omitted?
In PHP Variables are local by default, the keyword global defines them as
references to the global namespace.
There are some exceptions, like the availability of $this in methods or a
couple of predefined superglobal variables that are implicitly global in all
functions.
?php
$globalVar = 1;
$param = notshared;
$localVar = notshared;
function foo ($param) {
global $globalVar;
$localVar = (int) $param;
return $localVar + $localVar;
}
?
Given how much it works like global, the keyword lexical seems quite
consistent with the style of PHP.
Gesundheit
Wag
--
There’s a phrase we live by in America: “In God We Trust”. It’s right there
where Jesus would want it: on our money.
- Steven Colbert
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
CC to Christian Seiler
http://www.haskell.org/pipermail/haskell-cafe/2008-June/044379.html
http://www.haskell.org/pipermail/haskell-cafe/2008-June/thread.html
On Wednesday 18 June 2008, Luke Palmer wrote:
* A closure must be able to call itself recursively (via a
higher-order function typically)
I see two ways a closure might get a hold of itself, in order it can call
itself:
$f = function () {
lexical $whatever;
lexical $f; //get yourself by lexical scope
return $f();
};
$f();
$g = function ($g) { //get yourself by parameter
lexical $whatever;
return $g($g);
};
$g($g);
Getting the first version to work is somewhat tricky in a non-lazy language,
but it would be nice to have. The second should definately work.
I guess I'll download the patch and try.
* I would recommend only saving $this in the op_array structure if the
closure actually references $this -- if that is possible to deduce at
the time. Otherwise you might run into unexpected poor memory
performances in certain cases.
Agreed. A closure created inside an object should be able to outlive the
object by not holding a reference to it.
Since many PHP programmers put pretty much all of their functions into classes
for style reasons, which would mean most closures are created in the context
of an object, implicitly referencing $this might prevent a lot of objects
from being garbage-collected. Also, doesn't that turn all lambdas defined
inside an object into closures, which are heavier?
Between always referencing $this in a lamda and requiring lexical $this, the
latter seems like the smaller evil to me.
Gesundheit
Wag
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Tue, 2008-06-17 at 18:45 +0200, Karoly Negyesi wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. I program in Perl for a living, so hopefully you'll understand when I say (a) I would *never* want to use an implementation of closures like that. (b) Closures as proposed are *far* better than not having closures. jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
(a) I would *never* want to use an implementation of closures like that. (b) Closures as proposed are *far* better than not having closures. Could you elaborate on a) ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
I believe C# already has lambdas, and Java is supposed to be getting them. PHP is playing catchup, is all. (Oh, and Eiffel has 'agents', and I think I saw something about C++ Next Degeneration, and ...) Heck, the idea has only been around in computing since the 1950s... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 06:36 +0200, Karoly Negyesi wrote:
(a) I would *never* want to use an implementation of closures like that.
(b) Closures as proposed are *far* better than not having closures.
Could you elaborate on a) ?
I dislike the habit of implicit declaration --- strongly --- and the
consequent need for the lexical keyword (although at this point PHP's
stuck with it). I can see myself forgetting to use lexical far more
often than accidentally leaving off a `my' in Perl I should have used (I
hardly ever shadow variable names anyway, so if I forget `my' is usually
a use strict 'vars' error).
I dislike curly braces. Syntax that extends as far to the right as
possible tends to end up with fewer delimiters and a cleaner appearance.
It's basically a way to replace a bunch of closing braces with a
single ) or (in Haskell, implicit) ;
lintPat p0 $ \ ty0 - lintPat p1 $ \ ty1 - lint e
vs
lintPat($p0, sub { my ($ty0) = @_; lintPat($p1, sub { my ($ty1) = @_;
lint($e) })})
Four closing delimiters seems excessive.
Nit: `function' is verbose. ML uses fun or fn (I forget which and am
too lazy to google). Perl's regular keyword is sub, so they use that.
There are worse fates than duck typing (C++ comes to mind :), and given
a language with neither lexical closures/anonymous functions nor HM
typing, I'd complain about the lack of lambdas first. But, still, no HM
means no type classes. That ultimately becomes limiting. (I still
haven't seen a decent implementation of monads in a dynamically typed
language). But PHP is probably pretty much stuck with it.
Not to criticize, mind you --- the proposal looks excellent for what it
does. But I like what Haskell does worlds better.
jcc
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Not to criticize, mind you --- the proposal looks excellent for what it does. But I like what Haskell does worlds better. Obviously you like Haskell better given this mailing list :) I am not here to compare PHP and Haskell, I was just asking advice from people who know closures and lambdas very well and it seems that I got it in the words of the proposal looks excellent for what it does. Thanks a lot. Karoly Negyesi ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Hallo, Jules Bean wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Thanks Jules, I was starting to worry about Haskell-café. -alex http://www.ventonegro.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Paul: As you say, we are adult enougharound here to not need someone to look after us. So I don't need you or any other interfearing busybody to tell me what I can and can't say on Haskell Cafe. I expressed an opinion in a tongue-in-cheek way and at the end of my message expressed in clear terms that those were merely my views. Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... Paul: you're not making sense. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
With respect, I will not engage in further communication on that level. PR Stanley wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Paul: As you say, we are adult enougharound here to not need someone to look after us. So I don't need you or any other interfearing busybody to tell me what I can and can't say on Haskell Cafe. I expressed an opinion in a tongue-in-cheek way and at the end of my message expressed in clear terms that those were merely my views. Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... Paul: you're not making sense. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, Jun 18, 2008 at 1:42 PM, PR Stanley [EMAIL PROTECTED] wrote: Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! Just more evidence... http://en.wikipedia.org/wiki/Godwin's_law Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! Just more evidence... http://en.wikipedia.org/wiki/Godwin's_law Paul: I think you're missing a big painfully obvious point here, Mr smarty pants. No, actually, I think I'll leave it at that. I just can't be bothered. However, I'll say this - anyone sticking his bloody big hooter into my business in the future will get a similar reaction! Paul Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: Blimey! Talk about rearranging the deckchairs :-) Today's xkcd seems apropos: http://xkcd.com/438/ It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. I'm familiar with a lot of arguments for why PHP is a poorly-designed language, and have found them sufficiently persuasive that I haven't bothered to learn PHP. But I don't see any point to repeating those arguments on this list. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. I'm familiar with a lot of arguments for why PHP is a poorly-designed language, and have found them sufficiently persuasive that I haven't bothered to learn PHP. But I don't see any point to repeating those arguments on this list. Paul: So, you've never bothered to learn PHP. Well, I happen to know the language very well and therefore feel I am in a good position to express my views about it. Unlike you, I don't base my judgment on rumours and hearsay. It is true that PHP fails to capture the spirit of the classical concept of a function. Type checking in PHP is equally poor. These are not just my opinions. Are we not to say anything critical about a programming language even if it happens to be substantively relevant lestwe should offend someone? God, if you want to stick up for your mates here at least come up with a convincing cover. Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Tue, Jun 17, 2008 at 4:45 PM, Karoly Negyesi [EMAIL PROTECTED] wrote:
Hi,
The PHP community is discussing the adding of closures and lambdas to
the language, see the proposal at http://wiki.php.net/rfc/closures
If someone with knowledge of both languages could take a quick look it
would be great.
Thanks a lot
Karoly Negyesi
Ps. I am not a member of the PHP internals team, I am just a PHP
developer but I am very very interested in getting these in my
favourite language.
Whew. Well I suspect you weren't expecting that kind of reaction. Or
maybe you were... I used to be a Perl developer, and it didn't take
long before I got a level 12 resistence to flame...
Anyway, the proposal looks mostly okay. I don't know that much PHP,
but I find the lexical keyword to be a nuisance. What are the
semantics if the lexical keyword is omitted?(i.e. does the
variable become function-local, global, what?) If it is consistent
with the rest of the language, it'll do.
There is a much more important point with closures: their
implementation cannot be half-assed! I'm not claiming that the patch
is--I have not reviewed it--but there is nothing worse than coming up
with a design that relies on a language feature you only later find
out has been nerfed in some way. Story of my life in C#. And nerfed
closures are especially bad, because it's so hard to predict the code
path.
What I mean by this is the following must all be supported:
* A closure must only keep alive the varables it references, not the
whole pad on which they are allocated (Python messed up here)
* A closure must be able to call itself recursively (via a
higher-order function typically) (Squeak messed up here IIRC)
* Multiple references to the same body of code with different bindings
must be able to exist at the same time (duh, that's kinda what makes
it a closure)
* Closures must be nestable.
Looking over the Zend internal perspective section, it looks like
that implementation will mostly work. There are a couple of red
flags, though:
* I would recommend only saving $this in the op_array structure if the
closure actually references $this -- if that is possible to deduce at
the time. Otherwise you might run into unexpected poor memory
performances in certain cases. (This kind of thing can make an
*asymptotic* difference in memory performance; i.e. bringing the
memory usage of an algorithm from O(1) to O(n), for example)
* I'm worried that nested closures do not work properly with this
implementation sketch. Here's a test case:
$f = function ($y) {
return function ($z) {
return $y + $z;
}
};
$f(1)(2) # should give 3
And congratulations, PHP, for adopting a most essential and powerful feature!
Luke
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 18:19, Seth Gordon wrote: It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them wrong advises. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 16:00 +0100, PR Stanley wrote: It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. I could, and I think you're full of it, too. So there. jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. I could, and I think you're full of it, too. So there. Paul: I rest my case! :-) you cowardly hypocrit! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 9:46 am, Jules Bean wrote: This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. Reactions/arguments like the ones on this thread are perfect for Haskell - recursive and exponential. :) Could we have closure too? :-) Sorry, couldn't resist that one! Iain frequent firestarter and purveyor of bad puns ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
* A closure must only keep alive the varables it references, not the
whole pad on which they are allocated (Python messed up here)
Getting off subject, but I didn't know this about python. I'm not
saying you're incorrect, but my experimentation shows:
% cat t.py
class A(object):
def __init__(self, name): self.name = name
def __del__(self): print self.name, 'gone'
def f():
x = A('x')
y = A('y')
def g():
print x.name, 'alive'
return g
% python
Python 2.5.1 (r251:54869, Apr 18 2007, 22:08:04)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin
Type help, copyright, credits or license for more information.
import t
g = t.f()
y gone
g()
x alive
g.func_closure
#- (cell at 0xefb50: A object at 0xefb90,)
del g
x gone
%
So it looks to me like 'y' is not preserved by the closure returned by
'f', and you can see that in its func_closure which keeps the
reference to one A object, but not two.
Python closures do have a unique quirk, which is that variables
bound in a nested function are read-only. This is something that a
schemer might take issue with, but a haskeller probably wouldn't
notice :) And for the longest time python had its two space
namespace thing going on, so it wasn't even really lexically scoped,
but that's many years ago now.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17986275.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 09:46 +0100, Jules Bean wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules Hear, hear... Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules Hear, hear... Paul: You can shut up too, you bloody troll! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! I snipped Jonathan's message just because I was commenting on the tone of your response. Sorry if you think I presented your reply out of context, but my point is that I don't think there is any need for this in any context here. I do have a right to say that, even as someone who hardly ever posts but prefers to read the list...it's owned by everybody. This isn't the same thing as censorship and you'll notice I said norms, not rules of behaviour. No one's going to stop you making yourself look silly if you insist on doing it. As for Jonathan being too big for me, erm, who is he again? :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17987734.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
At 18:17 18/06/2008, you wrote: PR Stanley wrote: PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! I snipped Jonathan's message just because I was commenting on the tone of your response. Sorry if you think I presented your reply out of context, but my point is that I don't think there is any need for this in any context here. I do have a right to say that, even as someone who hardly ever posts but prefers to read the list...it's owned by everybody. This isn't the same thing as censorship and you'll notice I said norms, not rules of behaviour. No one's going to stop you making yourself look silly if you insist on doing it. As for Jonathan being too big for me, erm, who is he again? :-) Paul: So, now I am silly! I'd still prefer that to a coward and a hypocrite ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Hallo, PR Stanley wrote: Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Wow, Godwin's in record time. Please don't confuse freedom of speech with name-calling, or distasteful, non-constructive comments about someone else's programming language. Stop making yourself look like a fool. -alex http://www.ventonegro.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 4:36 pm, Karoly Negyesi wrote: (a) I would *never* want to use an implementation of closures like that. Could you elaborate on a) ? It wasn't me who wrote it, but consider - non-local variables are *not* captured unless you explicitly hoist them into the lambda expression using the 'lexical' keyword. - references to non-local variables that are not so hoisted are not syntax errors, they just quietly do something else. - ordinary functions do not act as if defined by lambda expressions; 'lexical' is required in lambdas and forbidden in functions. - ordinary functions do not act as if defined by lambda expressions; the latter can outlive their lexical scope, the former can't. - what you get is a reference to a variable (as you do in Scheme) but loop variables really are variables, not names for values, so lambdas created in different iterations of the same loop point so the same loop variable, and do not remember the value it had when they were created. The proposal explains how to work around this. All of this boils down to something in which you *can* with care do the things you expect to do with closures, but the language gently leads you to the edge of the Pit and the compiler just smiles quietly as you fall over. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Blimey! Talk about rearranging the deckchairs :-) With respect, do you not think it'd be wiser for the community to deal with a total lack of proper type checking, the lack of any notion of the general concept of a function, or a whole range of other fundamental issues in PHP first before worrying about closures and lambda functions? I'm no language purist but PHP really does take the biscuit. My personal views and not in any way representing the list . Paul At 17:45 17/06/2008, you wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. Thanks a lot Karoly Negyesi Ps. I am not a member of the PHP internals team, I am just a PHP developer but I am very very interested in getting these in my favourite language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Calm down, PR, that's not so bad, all we're going to see is an example of closures done wrong, nothing more. On 17 Jun 2008, at 21:46, PR Stanley wrote: Blimey! Talk about rearranging the deckchairs :-) With respect, do you not think it'd be wiser for the community to deal with a total lack of proper type checking, the lack of any notion of the general concept of a function, or a whole range of other fundamental issues in PHP first before worrying about closures and lambda functions? I'm no language purist but PHP really does take the biscuit. My personal views and not in any way representing the list . Paul At 17:45 17/06/2008, you wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. Thanks a lot Karoly Negyesi Ps. I am not a member of the PHP internals team, I am just a PHP developer but I am very very interested in getting these in my favourite language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
But all the cool kids have em! Seriously though computer languages are about getting things done. If this gets more things done for the PHP community in ways easier/simpler/faster than before then it's a win. They are after all /their/ deckchairs to play with. -ljr PR Stanley wrote: Blimey! Talk about rearranging the deckchairs :-) With respect, do you not think it'd be wiser for the community to deal with a total lack of proper type checking, the lack of any notion of the general concept of a function, or a whole range of other fundamental issues in PHP first before worrying about closures and lambda functions? I'm no language purist but PHP really does take the biscuit. My personal views and not in any way representing the list . Paul At 17:45 17/06/2008, you wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. Thanks a lot Karoly Negyesi Ps. I am not a member of the PHP internals team, I am just a PHP developer but I am very very interested in getting these in my favourite language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
But all the cool kids have em! Seriously though computer languages are about getting things done. If this gets more things done for the PHP community in ways easier/simpler/faster than before then it's a win. nerve gas would sort out the problem with mice in our building too, easier simpler faster than the stupid traps. They are after all /their/ deckchairs to play with. Yes, playing with deckchairs while the ship sinks with that bloody woman singing my Heart Will Go on. -ljr PR Stanley wrote: Blimey! Talk about rearranging the deckchairs :-) With respect, do you not think it'd be wiser for the community to deal with a total lack of proper type checking, the lack of any notion of the general concept of a function, or a whole range of other fundamental issues in PHP first before worrying about closures and lambda functions? I'm no language purist but PHP really does take the biscuit. My personal views and not in any way representing the list . Paul At 17:45 17/06/2008, you wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. Thanks a lot Karoly Negyesi Ps. I am not a member of the PHP internals team, I am just a PHP developer but I am very very interested in getting these in my favourite language. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
