parenscript-devel

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373 discussions

[parenscript-devel] No-op LETs shouldn't thwart the expressionizer
by Daniel Gackle 31 Jan '13

31 Jan '13

These two forms seem like they ought to generate the same code, but don't: (defun foo () (when (bar) (baz))) function foo() { return bar() ? baz() : null; }; (defun foo () (when (bar) (let () (baz)))) function foo() { if (bar()) { return baz(); }; }; Although one wouldn't write an empty LET by hand, macros that accumulate bindings sometimes emit them. If those macros are widely used in a program, one can lose quite a few desirable 'expressionizations' this way. I've committed a patch (see below) to tweak the function TRY-EXPRESSIONIZING-IF? into exempting empty LETs from the nesting heuristic it uses to decide what to expressionize. Vladimir, please revise or revert it I did it wrong. This came up because I'm trying to port my code to use the MAYBE-ONCE-ONLY macro introduced in a5cf0df, rather than a similar one I wrote. I'll post about that momentarily. Daniel diff --git a/src/special-operators.lisp b/src/special-operators.lisp index 0267133..799d70f 100644 --- a/src/special-operators.lisp +++ b/src/special-operators.lisp @@ -222,7 +222,8 @@ (try-expressionizing-if? (or (ignore-errors (ps-macroexpand x)) x) ;; fail (+ score (case (car exp) - ((if cond let) 1) + ((if cond) 1) + (let (if (second exp) 1 0)) ;; ignore empty binding list ((progn) (1- (length (cdr exp)))) (otherwise 0)))))) (t t)))

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[parenscript-devel] CoffeeScript Soaks
by David Sargeant 29 Jan '13

29 Jan '13

It would be great to be able to do "soaks" like in CoffeeScript. Example from coffeescript.org: zip = lottery.drawWinner?().address?.zipcode Produces var zip, _ref; zip = typeof lottery.drawWinner === "function" ? (_ref = lottery.drawWinner().address) != null ? _ref.zipcode : void 0 : void 0;

2 1

[parenscript-devel] DEFINE-PS-SYMBOL-MACRO
by David Sargeant 19 Jan '13

19 Jan '13

What does (DEFINE-PS-SYMBOL-MACRO symbol expansion) do? I found the following in non-cl.lisp, which got me thinking. (define-ps-symbol-macro {} (create)) Is there some way to extend the reader so that you could do {:name "David" :age 34} instead of (create :name "David" :age 34)? David

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[parenscript-devel] ++ and --
by David Sargeant 19 Jan '13

19 Jan '13

(++ x) => plus(x); and (-- x) => (x); Is this correct behavior? David

2 1

[parenscript-devel] Renaming a Macro
by David Sargeant 18 Jan '13

18 Jan '13

What is the best way to rename a macro in ParenScript? For example, if I wanted to use '->' instead of 'chain.' Right now I am just using a macro, but I'm wondering if there is an easier way. Thanks. (defmacro -> (&rest method-calls) `(chain ,@method-calls)) David

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[parenscript-devel] A more useful destructuring bind
by David Sargeant 18 Jan '13

18 Jan '13

The current DESTRUCTURING-BIND could be much more useful if you could pull apart objects and arrays. CoffeeScript has a great mechanism for this (http://coffeescript.org/#destructuring). Below is an example of what this macro might look like in parenscript. Let me know your thoughts. David (d-bind (:obj name (:obj firstname lastname) likes (:arr first-like second-like)) (create :name (create :firstname "Joe" :lastname "Blo") :occupation "Web Developer" :likes '("programming" "woodworking" "cycling")) (alert (+ "Your name is " firstname " and you like " first-like)))

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Re: [parenscript-devel] A more useful destructuring bind
by David Sargeant 17 Jan '13

17 Jan '13

The functionality in bind is really great. Are just you suggesting moving it out of parenscript proper? David

2 1

Re: [parenscript-devel] Loops that return a value
by David Sargeant 17 Jan '13

17 Jan '13

That code doesn't work properly in parenscript, btw. It does not decrement. (function () { var collect66 = []; for (var num = 10; num <= 1; num += 1) { collect66['push'](num); }; return collect66; })();

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[parenscript-devel] Loops that return a value
by David Sargeant 17 Jan '13

17 Jan '13

It seems that the looping constructs don't currently return a value. In other words, they don't return an array of the results. CoffeeScript allows for both scenarios, that is, looping for side-effects and looping that returns an array of results. I'm thinking it would be very useful to have dotimes*, dolist*, for-in*, etc. that return an array of results. Below is an example from coffeescript.org. Let me know what you think. David countdown = (num for num in [10..1]) ------------------------------------ var countdown, num; countdown = (function() { var _i, _results; _results = []; for (num = _i = 10; _i >= 1; num = --_i) { _results.push(num); } return _results; })();

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Re: [parenscript-devel] Loops that return a value
by David Sargeant 15 Jan '13

15 Jan '13

Holy cow. You lispers are awesome. The bind* solution to my problem is very elegant. Thanks so much for showing this to me. Parenscript is one of the coolest things I've come across in a while. David

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