World: r3wp
[Core] Discuss core issues
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Robert 30-Apr-2006 [4224x8] | and avoid dubplicating the storage code in every context, or write stub-functions that reference the storage stuff. |
Is it possible to bind the storage functions dynamically to the context that should be saved and switch this binding in the app depending on which context should be stored? | |
In other languages this is called delegates (IIRC). | |
Example: context A [a: 1 b: 2 c:3 list-words: none] context storage [list-words: does [probe first self]] | |
How can I execute storage/list-words in the context of A? So that I get back [a b c list-words] | |
I think I need to switch the way it works: do bind [first object] storage | |
Is this the correct way? | |
no it isn't... | |
Anton 30-Apr-2006 [4232x2] | >> c1: context [a: b: none] >> c2: context [a: b: none] >> do bind [a: 1 b: 2] c1 == 2 >> probe c1 make object! [ a: 1 b: 2 ] >> do bind [a: 100 b: 200] c2 == 200 >> probe c2 make object! [ a: 100 b: 200 ] |
Oh sorry, you specifically want to bind a function's body to the context. Let's see, I think this will work: bind second get in storage 'list-words A storage/list-words | |
Robert 30-Apr-2006 [4234] | What's this SECOND about? |
Anton 30-Apr-2006 [4235x3] | Just getting the function body. |
>> A: context [a: 1 b: 2 c: 3] >> storage: context [list-words: does [probe first self]] >> storage/list-words [self list-words] == [self list-words] >> bind second get in storage 'list-words A == [probe first self] >> storage/list-words [self a b c] == [self a b c] | |
read as: "bind the body of list-words to A" | |
Robert 30-Apr-2006 [4238] | Ok... now I think I got it. I was always trying to bind the WHOLE function, not only the body... |
Anton 30-Apr-2006 [4239x4] | Yes, bind needs a block! value, not a function! |
A function! is a more complex value, which contains a spec and a body. | |
You wouldn't want to bind the whole function, which would probably imply binding its spec block as well, since that would unlink the argument spec block relative to the body block. | |
Although, now that I think about it, that *could* be useful in some circumstance, maybe.... Many functions with similar argument lists could share a context. | |
Robert 30-Apr-2006 [4243] | ok. Thanks a lot. |
Anton 30-Apr-2006 [4244] | no problem.. |
Robert 30-Apr-2006 [4245x3] | I think I can bind a bunch of functions as well, right? |
I mean in one step. | |
So for example I specify a block of function names, that I want to bind. | |
Anton 30-Apr-2006 [4248] | You could append each function's body block to a single, large block. Then bind that. |
Robert 30-Apr-2006 [4249] | And it will keep it's link to the original function spec? |
Anton 30-Apr-2006 [4250x2] | blk: [] foreach func funcs [append blk second :func] bind blk ctx-A |
Yes, remember it's possible for same-named but differently-bound words to coexist together in a block. | |
Robert 30-Apr-2006 [4252] | Yes, but second FUNC doesn't return the function word. So where is this link kept? Or is the reference to the func body bound? |
Anton 30-Apr-2006 [4253x3] | example: >> blk: reduce [in system 'options in face 'options] == [options options] >> type? get blk/1 == object! >> type? get blk/2 == none! |
Are you talking about the words you have set to function values ? eg: my-word: func [][] | |
Each word has a single value slot (per context). | |
Robert 30-Apr-2006 [4256] | If I'm binding SECOND FUNC the body's reference is used, so this particular block is bound. Not a copy. |
Anton 30-Apr-2006 [4257] | Correct. |
Robert 30-Apr-2006 [4258x2] | Ok. |
The 'blk part doesn't work. I get an error for SECOND | |
Anton 30-Apr-2006 [4260x13] | Did you put function! values into the funcs input block ? |
eg: >> my-func: func [arg][print arg] >> funcs: reduce [:my-func] >> type? first funcs == function! | |
Hmm... it's not working.... | |
It doesn't look as simple operation as I thought... | |
That's weird. When you insert the function body into another block for binding it doesn't work. These two examples are not producing the same result: | |
>> ctx-A: context [a: 60] >> my-func: func [][a: 5] >> bind second :my-func ctx-A == [a: 5] >> ?? ctx-A ctx-A: make object! [ a: 60 ] >> my-func == 5 >> ?? ctx-A ctx-A: make object! [ a: 5 ] | |
>> ctx-A: context [a: 60] >> my-func: func [][a: 5] >> blk: [] append blk second :my-func == [a: 5] >> bind blk ctx-A == [a: 5] >> ?? ctx-A ctx-A: make object! [ a: 60 ] >> my-func == 5 >> ?? ctx-A ctx-A: make object! [ a: 60 ] | |
Insert copies the words into the block unbound from their original context. | |
Ok, so we can do this instead: | |
foreach func funcs [bind second :func ctx-A] | |
No reason for that not to work. | |
Yes, that works: | |
>> ctx-A: context [a: none] >> f1: does [a: 1] >> f2: does [a: 2] >> foreach func reduce [:f1 :f2][bind second :func ctx-A] == [a: 2] >> ?? ctx-A ctx-A: make object! [ a: none ] >> f1 == 1 >> ?? ctx-A ctx-A: make object! [ a: 1 ] >> f2 == 2 >> ?? ctx-A ctx-A: make object! [ a: 2 ] | |
Robert 30-Apr-2006 [4273] | This stuff is always really tricky. |
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