Re: Re: "do" blocks and method args problem

Given that this comes up every now and then (avg of once a year on this list it seems), I think it's worth considering changing the behaviour of do(). It only will have issues if people use = (not :=) inside do(). That's the only (as I can see) case where it could introduce subtle bugs. As far as I know however, no code does this (at least none of mine, and none of the standard lib code does).

Regards,

Jeremy Tregunna


On Thursday, 12 April, 2012 at 10:17 PM, dennisf486 wrote:

>    
> Haha OK I feel stupid, I just found "lexicalDo" in Io's C source code, it appears it does exactly that. Why doesn't lexicalDo show among the documented Object methods in the Io Reference on the website? And may I humbly suggest adding lexicalDo to the Guide and/or the Tutorial? I think this might be a pain point for new users of Io; I'm not arguing that the default behavior of regular "do" shouldn't be what it is, but I do think that it doesn't necessarily match a new user's intuition, especially if they come from "strongly lexically scoped" languages. Presenting "do" and "lexicalDo" side-by-side would both avert that potential confusion and be a primer for understanding scoping rules in Io in general.
>  
> --- In [email protected] (mailto:iolanguage%40yahoogroups.com), "dennisf486" <dennisf486@...> wrote:
> >
> > I hit a snag in my script refactoring. I'm trying to wrap all my proto creations inside methods so that I can pass dependencies as arguments, but I can't access the method arguments from inside a do block.
> >  
> > This works (because the appendProto is outside the do block):
> > // in file IdMap.io (http://IdMap.io)
> > method(namespace_std,
> > self IdMap := Object clone appendProto(namespace_std) do( /* other stuff */ ... )
> > )
> >  
> > This does not work (but I wish it did):
> > // in file IdMap.io (http://IdMap.io)
> > method(namespace_std,
> > self IdMap := Object clone do(
> > appendProto(namespace_std)
> > /* other stuff */
> > )
> >  
> > The problem is that the method argument "namespace_std" is not in scope inside the do-block. In the case of one appendProto I can easily move the declaration to the outside,
> > but this makes the declaration long when there are a lot of namespace-objects. And, I might want the argument for some other purpose than append proto.
> >  
> > I know that I could do something like:
> > self IdMap := Object clone
> > IdMap namespace_std := namespace std
> > IdMap do( ... )
> >  
> > But I'm trying to avoid the repetition of the word "IdMap".
> >  
> > I think one possible solution would be to make the method context a proto of the object:
> > method(namespace_std,
> > self IdMap := Object clone appendProto(thisLocalContext) do(
> > appendProto(namespace_std)
> > )
> >  
> > Is this the best / only way? One side effect of this trick is that all of the method invocation's locals / arguments are now permanently uncollectible, even if the args aren't all used, because thisLocalContext has a reference to them and the object has a reference to thisLocalContext. I suppose I could do something weird like appendProto(thisLocalContext) at the top of the file and removeProto(thisLocalContext) at the bottom of the file. If I do this it would make sense to make a method to do that automatically; I would call it "doInLocalContext".
> >  
> > Why doesn't Io have a doInLocalContext method already?
> >
>  
>