World: r3wp
[Core] Discuss core issues
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Steeve 30-Mar-2009 [13245] | error with swaping a: also b b: a |
Geomol 30-Mar-2009 [13246x2] | Hm, a SWAP command could be a good idea, maybe. Or just do: set [a b] reduce [b a] About freeing local variables, why would you do that? Don't you call your function several times? You give garbage collector more to do this way. If it's often the case, that locals should be freed, then maybe we need a new function type, that does that? (I'm asking all this, because I never understood the reason for having ALSO.) |
When I think about it, much of this is based on assumption how memory is handled in REBOL. We don't really know, because it's not documented. When is it good to free a local, and when not? There may be something wrong, if this should be handled by the programmer (also when it's not documented). | |
Steeve 30-Mar-2009 [13248] | In fact i use ALSO in functions to save the use of temporay variables. Instead of doing that: func [.. /local result][ .... result: ... ;*** compute result ... do something before returning the result :result ;** return the result ] I do: func [.. /local result][ .... also (compute the result) .(do something before returning the result) ] It saves the declaration of the result local var |
Geomol 30-Mar-2009 [13249] | Ok, your last func should have the /local result, right? |
Steeve 30-Mar-2009 [13250] | shouldn't have, right |
Geomol 30-Mar-2009 [13251] | Then it kinda makes sense. But then I think about all the internal sub-results, REBOL have to handle, and which I guess is freed by garbage collection. Is the problem, that REBOL keep locals, also when the funciton is finished? |
Steeve 30-Mar-2009 [13252] | In R3 it's not only to avoid the use of temporary vars, it's also faster (ALSO is native) |
Geomol 30-Mar-2009 [13253x4] | If I have a simple local in a language like C, I wouldn't allocate and free it every time, I call my function. |
A local in C is just a value stored in some memory. I guess, it's the same in REBOL? Again we don't really know. | |
REBOL must have a look-up table for the known words in the context, but after that it should just end up at a memory address. | |
If you free the local every time, REBOL have to allocate that memory every time. | |
Steeve 30-Mar-2009 [13257] | anyway ALSO is faster than using vars |
Geomol 30-Mar-2009 [13258] | ok |
Steeve 30-Mar-2009 [13259] | in R3 |
[unknown: 5] 30-Mar-2009 [13260x2] | Hi John, I free locals all the time. |
I use also function a lot. | |
Geomol 30-Mar-2009 [13262] | Have you tested performance when you free locals and if you don't? |
[unknown: 5] 30-Mar-2009 [13263] | I also use this clear-locals function which is very similiar to what Gabriele made: clear-locals: make function! [word][ word: bind? word set word none set in word first first word none ] |
Steeve 30-Mar-2009 [13264] | in R3 we don't need to free locals |
[unknown: 5] 30-Mar-2009 [13265x2] | John, I haven't done a lot of performance checking but I know the clear-locals function is working to free memory. |
I wish we could supress the garbabe collection and had the tools to handle that task ourselves. | |
Geomol 30-Mar-2009 [13267] | As I see it, it's the garbage collectors job. When I use large series, I declare them like this in my functions: some-series: clear [] Then I reuse the same memory, every time I call my function. I have never used ALSO. |
[unknown: 5] 30-Mar-2009 [13268] | yes, it is the garbage collectors job but any garbage collector has to make assumptions about the data that may not be to optimal to your application. |
Steeve 30-Mar-2009 [13269] | it's a differrent use case when dealing with series. even in R3 you need to clear the series |
eFishAnt 30-Mar-2009 [13270x2] | Has anyone done anything with REBOL and UNC (looks to me like UNC is M$ way of keeping networks and drives from being compatible, just like Paul Allen's backslash trick from long ago) http://technet.microsoft.com/en-us/library/cc939978.aspx where \\servername\sharepoint\subdirectory\filename. Almost looks like Microsoft took the "Refinement" concept of / and unrefined it with \ |
so, if I am on a M$ network, what is the best way to reach a \\blah\blah\blah\file.blah? | |
[unknown: 5] 30-Mar-2009 [13272x3] | I think it is: read %/blah/blah/blah/file.blah |
I know you can do it but just forget the syntax. | |
I don't have access to an open microsoft network currently. | |
eFishAnt 30-Mar-2009 [13275x2] | wow, thanks Paul. I think I freaked momenarily. If I have to do it through Windoze I figure I could do a call (as a backup plan) |
A link to where Gab answered this, and yes, your example looks correct, http://www.rebol.org/ml-display-thread.r?m=rmlJZJQ | |
Geomol 30-Mar-2009 [13277] | Is this a bug? >> first [:a/b] == :a/b >> type? first [:a/b] == path! Shouldn't it be get-path! ? |
Henrik 30-Mar-2009 [13278] | R3 responds get-path!, so it might be a bug |
Dockimbel 30-Mar-2009 [13279] | There's no get-path! datatype in R2 AFAICT. |
Geomol 30-Mar-2009 [13280x2] | I think, you are right! Just a bit confusing, what :a/b mean then. It doesn't give an error. |
Maybe a combined get-word! and path! ? | |
[unknown: 5] 30-Mar-2009 [13282x2] | It isn't a path either |
This is why I made my as-lit-word function. | |
Henrik 30-Mar-2009 [13284x2] | I think it's being interpreted as a get-word! with a refinement: >> type? :a/b ** Script Error: a has no value ** Where: halt-view ** Near: type? :a/b >> type? :a /b ** Script Error: a has no value ** Where: halt-view ** Near: type? :a /b >> |
and inside the block, it can be interpreted as a path. basically get-path! is a good idea. :-) | |
[unknown: 5] 30-Mar-2009 [13286] | >> as-lit-word? first [:a/b] == false >> as-lit-word? first [:a] == true |
Henrik 30-Mar-2009 [13287] | I'm not sure what that means... |
[unknown: 5] 30-Mar-2009 [13288x4] | Tells me if an item acts as a lit-word. |
acts is the key word. | |
http://www.tretbase.com/forum/viewtopic.php?f=8&t=30&start=10#p141 | |
I could test the value with the as-lit-word? function to determine if I want to set the word to a value. | |
Dockimbel 30-Mar-2009 [13292] | It seems that there's no specific semantic rule in R2 for a get-word! as first item of a path! value. So, it's just treated as word!. >> a: [b 123] == [b 123] >> :a/b == 123 >> a/b == 123 |
Gabriele 31-Mar-2009 [13293x2] | Geomol: the best exaple is: also copy port close port |
but it's so useful in so many cases... | |
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