August 2010 - parenscript-devel - mailman3.common-lisp.net

[parenscript-devel] Patch: added JS label/break to PS
by Daniel Gackle 06 Dec '10

06 Dec '10

I just pushed a patch (authored by Scott) to implement JS's LABEL and BREAK in PS. (Note that this patch deprecates LABELED-FOR since you can get the same effect by combining LABEL and FOR. Was anybody using LABELED-FOR?) Here's an example: (label scope (foo) (when (bar) (break scope)) (blee)) => scope: { foo(); if (bar()) { break scope; }; blee(); }; I was astonished to discover recently that JS has supported this ability all along in the form of labeled statements and labeled breaks. I'd always assumed that to get explicit returns from an arbitrary scope, you'd have to resort to the ugly hack of muscling TRY/CATCH to do it, thinking that this was the closest JS counterpart. (See http://news.ycombinator.com/item?id=793092 for a thread in which several people believe this.) But it appears we were all wrong. What's not clear yet is how far this can be taken. Can you use it inside a nested local function to return immediately from the top-level function? That is one thing I've wanted for a long time. In the ideal case, LABEL/BREAK could be used as a base for implementing a proper BLOCK and RETURN-FROM in PS, something which we'd long believed to be impossible. One challenge is that in CL, RETURN-FROM can take a value, which becomes the value of BLOCK. In other words, BLOCK in CL is an expression while LABEL in JS is not. It seems, though, that most of this challenge has already been conquered with the development of implicit return in PS. The only thing you'd need to add is detecting when BLOCK is being used as an expression, declaring a gensymed variable and assigning whatever is happening inside BLOCK to that variable (much like implicit return already does with e.g. CASE), then put the variable in the expression position that BLOCK was in. It seems like this ought to work. It would also make things like this possible in PS: (1+ (case foo (:eleven 11) (:twelve 12))) Vladimir (and everybody), is the above clear? What do you think of it? Daniel

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[parenscript-devel] in-package and Parenscript compilation
by Alessio Stalla 06 Nov '10

06 Nov '10

Greetings, I'm approaching Parenscript and I must say I'm really impressed by this library. Kudos to the developers! But I find one thing missing: the Parenscript stream/file compiler does not understand in-package forms like the CL file compiler does; rather, it reads all the forms in the package which is current at the time it gets called. This makes it slightly inconvenient to compile Lisp files which need to be read in a certain package, and completely impossible to handle files which change *package* mid-file (which is generally not a good idea, but still it's possible in CL). I'm attaching a patch against src/compilation-interface.lisp to make the compiler behave like the CL one; comments are welcome. Regards, Alessio Stalla

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[parenscript-devel] Parenscript condition system implemented for PSOS
by Red Daly 01 Oct '10

01 Oct '10

I have added a Common Lisp-like condition system to the Parenscript Object System (PSOS). Parenscript now has HANDLER-BIND, HANDLER-CASE, RESTART-CASE, RESTART-BIND, INVOKE-RESTART, and SIGNAL. The patch that adds this is here: http://github.com/gonzojive/paren-psos/commit/6578ad223515dc2c1ddf49346f4ba… and totals about 200 lines, plus 200 lines of test cases. It could probably work without a type system at all, but it will require some runtime code no matter what. The whole PSOS system is backed by a test suite that uses CL-Spidermonkey. Take a look at PSOS here: http://github.com/gonzojive/paren-psos for more details. Enjoy! Red

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[parenscript-devel] How to generate comments?
by Bastian Müller 24 Aug '10

24 Aug '10

Hi, Sorry if this has been asked already earlier here on the list. I looked into the reference documentation, but couldn't find anything. Is it possible to generate JavaScript comments, or even more generalized, inline any JavaScript inside parenscript code? Thanks! Cheers, Bastian

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[parenscript-devel] CONCAT-STRING
by Daniel Gackle 24 Aug '10

24 Aug '10

I was just looking at CONCAT-STRING in the file macros.lisp. This name is misleading, I think, since the arguments need not be strings. (They get converted to strings if necessary.) Perhaps CONCAT-TO-STRING or STRINGIFY? I prefer the latter for brevity.

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[parenscript-devel] Tighter keyword arguments?
by Daniel Gackle 23 Aug '10

23 Aug '10

The code that's generated for a keyword argument goes like this: (ps (defun foo (&key a) (bar a))) => (abbreviated for clarity): "function foo() { var a; // ... pick out and assign keyword args ... if (a === undefined) { a = null; }; return bar(a); };" It seems to me that this could be made tighter as follows: "function foo() { var a = null; // ... pick out and assign keyword args ... return bar(a); };" The only difference I can think of is when someone explicitly passes undefined as a value for the argument, but that's an oxymoronic thing to do. Can anyone think of a reason not to make this change? I like PS's keyword arguments a lot, but the generated JS is bloated enough to make me wince.

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[parenscript-devel] Expressionize
by Red Daly 20 Aug '10

20 Aug '10

The 'expressionize' function seems to be at the core of implicit returns. It seems to be a promising approach to morphing Javascript into an everything-is-an-expression language. Unfortunately right now it is poorly documented and not used everywhere it could be. Hopefully we can discuss where this feature is heading publicly and finish up expressionizing parenscript. Right now LET does not seem to take advantage of expressionize the same way functions do. LET fails to turn TRY into an expression, while implicit return works. What would we need to do to add this? (ps:ps (let ((x (ps:try xxx (:catch (x) 5)))) x)) "var x233 = try { xxx; } catch (x) { 5; }; x233;" below works: > (ps:ps (lambda () (ps:try xxx (:catch (x) 5)))) "function () { try { return xxx; } catch (x) { return 5; }; };" Thanks for the insights, Red

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[parenscript-devel] Duplicate variable declarations
by Daniel Gackle 16 Aug '10

16 Aug '10

When PS hoists the declaration of a variable, it should probably check for duplicates: (ps (defun blah () (list (let ((foo 12)) (* foo 2)) (let ((foo 13)) (* foo 3))))) => "function blah() { var foo; var foo; return [(foo = 12, foo * 2), (foo = 13, foo * 3)]; };"

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[parenscript-devel] Fwd: Parenscript
by Nick Fitzgerald 08 Aug '10

08 Aug '10

Hey Dan, Thanks for the tip regarding the tutorial, however I'm not sure who wrote it or who is maintaining it. I am forwarding your message to the ParenScript development mailing list; I'm sure someone there will be more helpful than me. Thanks again, _Nick_ ---------- Forwarded message ---------- From: Daniel Weinreb <dlw(a)itasoftware.com> Date: Wed, Jul 28, 2010 at 2:01 PM Subject: Parenscript To: Nick Fitzgerald <fitzgen(a)gmail.com> Nick, Hi. I just got reminded of the existence of Parenscript by seeing the recent Planet Lisp blog post. This is really cool and I hope to get the time to learn all about it. I have one tiny suggestion: in this tutorial: http://common-lisp.net/project/parenscript/tutorial.html put in a reference to something that explains what Parenscript is for, what it's all about. If one stumbles onto the tutorial, one has a hard time figuring out what's going on, lacking any context. -- Dan

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[parenscript-devel] TryParenScript.com!
by Nick Fitzgerald 05 Aug '10

05 Aug '10

Hey guys! I just got a quick and dirty first iteration of http://tryparenscript.com/ up and running. Emphasis on dirty. This is my first "real" piece of ParenScript, so I would love to have some feedback. All of the code is hosted at http://github.com/fitzgen/tryparenscript.com It follows in the footsteps of http://www.tryruby.org/, http://tryhaskell.org/, and http://tryclj.licenser.net/. Basically provides a REPL for ParenScript inside of your browser. I would like to add an interactive tutorial like how some of those have in the future. I couldn't get sbcl and hunchentoot running behind apache, it was a nightmare for me (though I expect I just was overlooking something), so I ended up writing the backend in ParenScript too, with Node JS. Currently there are some issues with the way that function definitions are evaled in the global scope, so (defun foo (x) (return (+ x 1))) won't create a new global foo function because it ends up being evaluated as this: window.__tryps_return = function foo(x) { return x + 1; } so what should have been a Function Declaration gets turned in to a Named Function Expression. This is on the top of my list of things to do next. Fortunately, there is a simple (while not quite "easy-to-use") fix: (setf (@ window foo) (lambda (x) (return (+ x 1)))) which will work as expected. I also expect I will need to set up some type of monitoring for the server because it is just a single process in detachtty, and if it crashes (which I suspect it might if it hit the front page of Hacker News all of a sudden, or something like that) I would have to go back in and restart the process (after I somehow found out it died). This is obviously less than optimal. If anyone has any suggestions on this front, I would love to hear them too. Most of all, I would just like to get some feedback and suggestions on the code :) Thanks in advance for all your responses! _Nick_

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