[parenscript-devel] Why is there a WITH clause in my loop?
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel
The WITH clause is there to make sure that lambdas capture a fresh binding of loop-local variables per iteration (otherwise they'd all share the same binding which would get incremented on every loop iteration). I'm guessing the reason your code doesn't run across this bug is that the lambda that captures time gets called once per iteration and discarded. Vladimir 2010/12/7 Daniel Gackle <danielgackle@gmail.com>:
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel _______________________________________________ parenscript-devel mailing list parenscript-devel@common-lisp.net http://common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
Hi, I have just installed the latest version of Parencript. In detail I did : 1) downloaded parenscript-2.2 and anaphora-0.9.3 and saved it in : /var/clfree/anaphora-0.9.3 /var/clfree/parenscript-2.2 2) I load with asdf (defun asdf-register (library) (pushnew library asdf:*central-registry* :test #'equal)) (defun asdf-load (x) (asdf:operate 'asdf:load-op x)) (defun asdf-require (x y) (asdf-register x) (asdf-load y)) (asdf-require "/var/clfree/anaphora-0.9.3/" :anaphora) (asdf-require "/var/clfree/parenscript-2.2/" :parenscript) Next I try it : a) (ps:ps (slot-value obj 'foo)) --> * Warning: SLOT-VALUE is deprecated, use GETPROP instead "obj.foo;" b) (ps:ps (getprop obj 'foo)) --> "getprop(obj, 'foo');" It doesn't seem to recognize getprop. Neither does it recognize chain and create. My older version still works ok. Any idea what I did wrong, or have overlooked ? Thanks in advance. Wout Perquin
On 12/13/10, Wout Perquin <wout.perquin@skynet.be> wrote:
Hi,
I have just installed the latest version of Parencript. In detail I did : 1) downloaded parenscript-2.2 and anaphora-0.9.3 and saved it in : /var/clfree/anaphora-0.9.3 /var/clfree/parenscript-2.2
2) I load with asdf (defun asdf-register (library) (pushnew library asdf:*central-registry* :test #'equal)) (defun asdf-load (x) (asdf:operate 'asdf:load-op x)) (defun asdf-require (x y) (asdf-register x) (asdf-load y)) (asdf-require "/var/clfree/anaphora-0.9.3/" :anaphora) (asdf-require "/var/clfree/parenscript-2.2/" :parenscript)
Next I try it : a) (ps:ps (slot-value obj 'foo)) --> * Warning: SLOT-VALUE is deprecated, use GETPROP instead "obj.foo;"
b) (ps:ps (getprop obj 'foo)) --> "getprop(obj, 'foo');"
It doesn't seem to recognize getprop. Neither does it recognize chain and create. My older version still works ok.
Any idea what I did wrong, or have overlooked ?
Have you got the right package? That should be ps:getprop, not cl-user::getprop. That's the obvious thing I can think of right now. Hope that helps. :-) Yong.
Yeah, looks like the wrong package. Also, you should use Quicklisp to get Parenscript, it sets up everything automatically: http://www.quicklisp.org/beta/ Vladimir 2010/12/13 Theam Yong Chew <senatorzergling@gmail.com>:
On 12/13/10, Wout Perquin <wout.perquin@skynet.be> wrote:
Hi,
I have just installed the latest version of Parencript. In detail I did : 1) downloaded parenscript-2.2 and anaphora-0.9.3 and saved it in : /var/clfree/anaphora-0.9.3 /var/clfree/parenscript-2.2
2) I load with asdf (defun asdf-register (library) (pushnew library asdf:*central-registry* :test #'equal)) (defun asdf-load (x) (asdf:operate 'asdf:load-op x)) (defun asdf-require (x y) (asdf-register x) (asdf-load y)) (asdf-require "/var/clfree/anaphora-0.9.3/" :anaphora) (asdf-require "/var/clfree/parenscript-2.2/" :parenscript)
Next I try it : a) (ps:ps (slot-value obj 'foo)) --> * Warning: SLOT-VALUE is deprecated, use GETPROP instead "obj.foo;"
b) (ps:ps (getprop obj 'foo)) --> "getprop(obj, 'foo');"
It doesn't seem to recognize getprop. Neither does it recognize chain and create. My older version still works ok.
Any idea what I did wrong, or have overlooked ?
Have you got the right package? That should be ps:getprop, not cl-user::getprop. That's the obvious thing I can think of right now.
Hope that helps. :-)
Yong.
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I'm running to this WITH clause in a number of places, but can't see the (potential) bug you describe in any of them. Can you provide an example of this bug (that necessitates the WITH)? I don't get it yet. Daniel 2010/12/10 Vladimir Sedach <vsedach@gmail.com>
The WITH clause is there to make sure that lambdas capture a fresh binding of loop-local variables per iteration (otherwise they'd all share the same binding which would get incremented on every loop iteration).
I'm guessing the reason your code doesn't run across this bug is that the lambda that captures time gets called once per iteration and discarded.
Vladimir
2010/12/7 Daniel Gackle <danielgackle@gmail.com>:
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel _______________________________________________ parenscript-devel mailing list parenscript-devel@common-lisp.net http://common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
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Specifically, I'm having a hard time seeing how this: function blah(obj) { for (var key in obj) { with ({ x : null }) { var x = []; // do anything at all here... can ever be better than this: function blah(obj) { for (var key in obj) { var x = []; // do that thing here instead... What am I missing? 2011/1/28 Daniel Gackle <danielgackle@gmail.com>
I'm running to this WITH clause in a number of places, but can't see the (potential) bug you describe in any of them. Can you provide an example of this bug (that necessitates the WITH)? I don't get it yet.
Daniel
2010/12/10 Vladimir Sedach <vsedach@gmail.com>
The WITH clause is there to make sure that lambdas capture a fresh
binding of loop-local variables per iteration (otherwise they'd all share the same binding which would get incremented on every loop iteration).
I'm guessing the reason your code doesn't run across this bug is that the lambda that captures time gets called once per iteration and discarded.
Vladimir
2010/12/7 Daniel Gackle <danielgackle@gmail.com>:
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel _______________________________________________ parenscript-devel mailing list parenscript-devel@common-lisp.net http://common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
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Not sure if you know this or not, but JavaScript doesn't have block scope like C and others do: var statements get "hoisted" to the top of the current function. The following two foos are pretty much equivalent: function foo(obj) { for (var key in obj) { var x = []; doStuffWith(x); } } function foo(obj) { var x = undefined, key = undefined; for (key in obj) { x = []; doStuffWith(x); } } Hope I have helped out just a little :) _Nick_ 2011/1/28 Daniel Gackle <danielgackle@gmail.com>
Specifically, I'm having a hard time seeing how this:
function blah(obj) { for (var key in obj) { with ({ x : null }) { var x = []; // do anything at all here...
can ever be better than this:
function blah(obj) { for (var key in obj) { var x = []; // do that thing here instead...
What am I missing?
2011/1/28 Daniel Gackle <danielgackle@gmail.com>
I'm running to this WITH clause in a number of places, but can't see
the (potential) bug you describe in any of them. Can you provide an example of this bug (that necessitates the WITH)? I don't get it yet.
Daniel
2010/12/10 Vladimir Sedach <vsedach@gmail.com>
The WITH clause is there to make sure that lambdas capture a fresh
binding of loop-local variables per iteration (otherwise they'd all share the same binding which would get incremented on every loop iteration).
I'm guessing the reason your code doesn't run across this bug is that the lambda that captures time gets called once per iteration and discarded.
Vladimir
2010/12/7 Daniel Gackle <danielgackle@gmail.com>:
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel _______________________________________________ parenscript-devel mailing list parenscript-devel@common-lisp.net http://common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
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The 'with' only happens if there's a lambda capturing the loop variables. Consider this code: (let ((foo (make-array 3))) (dotimes (i 3) (setf (aref foo i) (lambda () i))) (funcall (@ console log) (funcall (aref foo 0))) (funcall (@ console log) (funcall (aref foo 1))) (funcall (@ console log) (funcall (aref foo 2)))) With 'with': var foo = new Array(3); for (var i = 0; i < 3; i += 1) { with ({ i : i }) { foo[i] = function () { return i; }; }; }; console.log(foo[0]()); console.log(foo[1]()); console.log(foo[2]()); => 0 1 2 Without 'with': var foo = new Array(3); for (var i = 0; i < 3; i += 1) { foo[i] = function () { return i; }; }; console.log(foo[0]()); console.log(foo[1]()); console.log(foo[2]()); => 3 3 3 Vladimir 2011/1/28 Daniel Gackle <danielgackle@gmail.com>:
Specifically, I'm having a hard time seeing how this: function blah(obj) { for (var key in obj) { with ({ x : null }) { var x = []; // do anything at all here... can ever be better than this: function blah(obj) { for (var key in obj) { var x = []; // do that thing here instead... What am I missing?
2011/1/28 Daniel Gackle <danielgackle@gmail.com>
I'm running to this WITH clause in a number of places, but can't see the (potential) bug you describe in any of them. Can you provide an example of this bug (that necessitates the WITH)? I don't get it yet. Daniel
2010/12/10 Vladimir Sedach <vsedach@gmail.com>
The WITH clause is there to make sure that lambdas capture a fresh binding of loop-local variables per iteration (otherwise they'd all share the same binding which would get incremented on every loop iteration).
I'm guessing the reason your code doesn't run across this bug is that the lambda that captures time gets called once per iteration and discarded.
Vladimir
2010/12/7 Daniel Gackle <danielgackle@gmail.com>:
Here's a really strange one. We have a form like the following. I've stripped it down for brevity, so it looks weird: (loop :for time :from time1 :below time2 :do (when (foo (λ () (bar (λ () (blah)) time)) time) (break))) It used to generate this: for (var time = time1; time < time2; time += 1) { if (foo(function () { return barr(function () { return blah(); }, time); }, time)) { break; }; }; But now it generates this: for (var time = time1; time < time2; time += 1) { with ({ time : time }) { if (foo(function () { return bar(function () { return blah(); }, time); }, time)) { break; }; }; }; That is one weird WITH clause in there! No doubt it has something to do with lexical scoping magic going on under the hood. But I definitely don't want it in a performance-critical loop. Daniel _______________________________________________ parenscript-devel mailing list parenscript-devel@common-lisp.net http://common-lisp.net/cgi-bin/mailman/listinfo/parenscript-devel
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participants (5)
-
Daniel Gackle -
Nick Fitzgerald -
Theam Yong Chew -
Vladimir Sedach -
Wout Perquin