[e-lang] Need help with program analysis for Transparent auditor (or: code zippers)

[David-Sarah Hopwood]

David-Sarah Hopwood wrote:
> Kevin Reid wrote:
>> I've thought of two possible solutions so far:
>>
>> 1. Starting from EMethod(..., "a", ...), scan its children for  
>> occurrences of NounExpr("foo") and reject any which bind it. This  
>> would reject more than it needs to.
>>
>> 2. Switch to a pre-processing stage (instead of the incremental  
>> operation of a zipper) to assign an identity (or a mutable analysis- 
>> information field, equivalently) to each variable binding and all of  
>> its uses, and add upward references (like in the zipper) to each  
>> node; this would make the is-this-foo-that-foo test a simple comparison.
>> At the moment, the second option seems attractive; tying uses to  
>> definitions of variables in a generic fashion should be useful for  
>> other types of analysis. And since this is strictly analysis, not  
>> transformation, I don't need the modify-without-mutation function of  
>> a zipper. The only reason I haven't done that yet is I think zippers  
>> are neat (and there might be other uses for an established zipper  
>> over E ASTs).
> 
> The second option is called "Barendregt's convention".

I intended to give a reference:

H. P. Barendregt. The lambda calculus. Its syntax and semantics.
NorthHolland Publishing Co., Amsterdam, 1980 (or revised edition, 1984).

-- 
David-Sarah Hopwood