Smalltalk source access in BlockClosure

2014-04-04 10:18 GMT-07:00 Siemen Baader <[hidden email]>:

Hi list,

Hello,

 

I'm building a metaprogramming system in Amber, and I need to edit the Smalltalk source of BlockClosures at run time. Is there a way to do this? If not, should we have one? Is it possible in other smalltalks?

It is possible in other smalltalks such as Pharo/Squeak/VisualWorks. 

In Amber you may have some issues.

One thing is that you need the amber compiler to be able to do that, which is usually not in a production amber application (but you could add it).

Another issue is that in case of javascript callbacks you cannot access the blockClosure source so you cannot know what part of the code to edit. example:

 jQuery 

getJSON: filePath

onSuccess: [:data | self callback: data].

It is impossible to get the source of this block '[:data | self callback: data]' at runtime because the javascript runtime lacks this feature.

But for most blocks it should be possible. You can look at how the debugger maps the closure to its source and enclosing method, then you'll just need to recompile the method enclosing the block with your new source.

Ideally, I'd also like to have access to the objects bound in the BlockClosures's scope. Is that possible?

In Pharo/Squeak/VisualWorks you can do it by inspecting the closure (the indexable fields of the closure are the objects bound to the closure scope). I tried in Amber and I didn't succeed to do it. As Amber's closures are bound to javascript functions, it may not be possible due to javascript lacking the feature...

best,
Siemen

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I'm building a metaprogramming system in Amber, and I need to edit the Smalltalk source of BlockClosures at run time. Is there a way to do this? If not, should we have one? Is it possible in other smalltalks?

One thing is that you need the amber compiler to be able to do that, which is usually not in a production amber application (but you could add it).

Another issue is that in case of javascript callbacks you cannot access the blockClosure source so you cannot know what part of the code to edit. example:

 jQuery 

getJSON: filePath

onSuccess: [:data | self callback: data].

It is impossible to get the source of this block '[:data | self callback: data]' at runtime because the javascript runtime lacks this feature.

But for most blocks it should be possible. You can look at how the debugger maps the closure to its source and enclosing method, then you'll just need to recompile the method enclosing the block with your new source.

Ideally, I'd also like to have access to the objects bound in the BlockClosures's scope. Is that possible?

In Pharo/Squeak/VisualWorks you can do it by inspecting the closure (the indexable fields of the closure are the objects bound to the closure scope). I tried in Amber and I didn't succeed to do it. As Amber's closures are bound to javascript functions, it may not be possible due to javascript lacking the feature...