World: r3wp
[Core] Discuss core issues
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[unknown: 5] 20-Dec-2008 [11732] | I agree |
BrianH 20-Dec-2008 [11733] | Remember, all of the parameters are locals, not just the ones after the /locals refinement. |
[unknown: 5] 20-Dec-2008 [11734] | yeah true. We should be setting the args to none also. |
BrianH 20-Dec-2008 [11735] | If you don't want to corrupt things before you return the value from the function, use ALSO - that is what it was designed for. |
[unknown: 5] 20-Dec-2008 [11736] | Yeah I love Also Brian and glad you implemented that. But this is really related to all the other non returned values. |
BrianH 20-Dec-2008 [11737] | R3 doesn't have this problem, so you are not likely to get a native. |
Geomol 20-Dec-2008 [11738] | :-) It gets worse, if all parameters should be set to none: f: func [v /local a b c][ a: 1 b: 2 c: 3 print [v a b c] set bind head remove find first :f /local 'a none print [v a b c] ] Try: >> f 42 |
BrianH 20-Dec-2008 [11739] | Keep in mind that unless you have a known name reference to a function, the code inside the function has no idea which function it is inside, so a native would need a reference to a function or a word with the function assigned to it or it won't work - natives aren't magic. |
Geomol 20-Dec-2008 [11740x3] | Hm, I don't need the HEAD, so it can be: set bind remove find first :f /local 'a none |
Brian, do you know, if it's possible from outside a function to specity its context? (To be used in the second parameter for BIND.) | |
*specify* | |
BrianH 20-Dec-2008 [11743] | You don't need the find either. John, your example with ALSO: f: func [v /local a b c][ a: 1 b: 2 c: 3 print [v a b c] also print [v a b c] set bind remove first :f 'a none ] |
Geomol 20-Dec-2008 [11744x3] | nah, doen't work. |
*doesn't* | |
:-) It has to find the /local and remove it. | |
[unknown: 5] 20-Dec-2008 [11747x2] | use difference |
difference first :f [/local] | |
BrianH 20-Dec-2008 [11749] | In answer to your question, in R2 it is only possible from outside a function to retrieve its context. You were doing so in your example. It doesn't have any meaning when the function isn't running, but you can't get a reference to the function from the inside. |
[unknown: 5] 20-Dec-2008 [11750x2] | But Brian, what if an other function is called inside the function your trying to release from? |
just as an ending line in your function that says: clear-locals this-function | |
Geomol 20-Dec-2008 [11752] | I was thinking about making a clear-locals function, but then I need to access the context of the function calling clear-locals (from clear-locals). |
BrianH 20-Dec-2008 [11753x2] | Remember, the /local refinement is also a local variable, so if you want to clear *all* the locals you also need to clear the word versions of the refinements. |
For the most part you don't need to clear *all* of the locals, just a select few that still refer to large series or structures. | |
[unknown: 5] 20-Dec-2008 [11755] | Brian, it is one of those "While were at it" scenarios |
BrianH 20-Dec-2008 [11756] | John, you can't just access the context of a calling function or even the current function, even from a native. The code block your code is in can be assigned to many functions, and isn't bound to any context. Words are direct bound individually. If you want to clear a context, yo have to specify which one in a parameter. |
Steeve 20-Dec-2008 [11757x4] | fun: func [spec body /local me][ me: construct append copy/deep [ clear-all: [set bind copy next next first self self none] ] body me/clear-all: does me/clear-all clear find spec /local func spec bind body me ] f: fun [/local c d ][ c: d: 1 probe self print [c d ] clear-all print [c d]] f |
a function with a context for local vars | |
but not perfect, all vars which are set (including globals) are redefined as locals | |
but there is an idea | |
BrianH 20-Dec-2008 [11761] | You can't get access to a function's context without having a known word that is already bouund to that context. When you do first :f, the words retrn are not bound to the function's context. In R2, when you do third :f you get words that are bound, but you can only guess to what., since words are bound individually. The only safe way to do clear-words is to pass both the function and a known word bound to the function's context, and even then you have to copy the fuunction's argument block and convert any refinements to words before you bind the copy. |
[unknown: 5] 20-Dec-2008 [11762x4] | exactly |
that is why I'm attempting this with third and using clear-locals :func :arg | |
actually :fnc | |
not got it yet though | |
BrianH 20-Dec-2008 [11766] | You can't assme that any of the words in the block retuurned by third are bound to the function's context, even if they are spelled the same as argument words or refinements. |
[unknown: 5] 20-Dec-2008 [11767] | why not? |
BrianH 20-Dec-2008 [11768x2] | Sorry, I meant second. Second returns the code block. The first and third blocks are definitely *not* bound to the function's context. |
I mean the words in those blocks. The blocks themselves can't be bound at all - only words can be bound. | |
[unknown: 5] 20-Dec-2008 [11770] | So brianH are you saying it is impossible in R2 to send a function within a func to clear the parent functions locals? |
BrianH 20-Dec-2008 [11771x4] | No, just difficult unless you provide 2 parameters: - A reference to the function or a copy of its parameter list. - A word known to be bound to the function's context. |
Even then, it is not very efficient. You are better off clearing select words explicitly. | |
This is part of why R3's function contexts are different: to make this kind of thing unnecessary. | |
As a side effect, the clear-words function would be impossible in R3. | |
[unknown: 5] 20-Dec-2008 [11775] | What part would be inefficient? |
BrianH 20-Dec-2008 [11776] | Getting a the argument list, which you would have to copy, convert refinements to words, then bind. The copy and conversion would be slower than necessary. |
[unknown: 5] 20-Dec-2008 [11777x3] | Yeah I don't know if the overhead is worth it. |
R3 in 09? | |
Hmm.. I should sell T-shirts with that on it. | |
BrianH 20-Dec-2008 [11780] | Developer releases at least, and maybe before then. |
[unknown: 5] 20-Dec-2008 [11781] | Everyone would ask "What is R3?" and then we could tell them about REBOL. |
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