[plt-scheme] find-method/who

From: Doug Orleans (dougo at place.org)
Date: Sat Mar 19 21:22:56 EST 2005

Matthew Flatt writes:
 > At Wed, 9 Mar 2005 20:46:55 -0500, Doug Orleans wrote:
 > >  > 
 > >  > If you're writing a program-processing tool, you'll need to recertify
 > >  > expressions that you assemble from pieces of pulled-apart expressions.
 > >  > Or, if you don't care about discarding the enforcement power of
 > >  > certificates, you can just recertify every expression as soon as you
 > >  > extract it from an enclosing expression.
 > > 
 > > OK, I think I'm starting to grok this, but I'm not sure if I'm doing
 > > the recertify correctly.  Should I be using `syntax-recertify', or
 > > `syntax-local-recertifier', or both? 
 > If you're writing a program processor, use `syntax-recertify'. The
 > `syntax-local-recertifier' procedure is for macros.

By "program processor" do you just mean a procedure that operates on
syntax objects?  When if I have a macro that uses a program processor?

 > > What should
 > > I use as the inspector, `(current-code-inspector)'?  
 > Yes.

OK.  I noticed that errortrace uses (current-inspector), is this a
signficant difference?

 > > What do I use as
 > > the certificate key?  Can I just use #f? 
 > Yes.
 > > Do you have an example of recertification?
 > Not a small one, but there's errortrace and the "src2src.ss" part of mzc.

Thanks, I figured out what I was doing wrong; I'm pulling out
identifiers from a syntax object (the free variables of the
expression), and I have to recertify them with each enclosing
expression's syntax object, not just the top level one.  (You can see
the code on SourceForge if you're morbidly curious:
Tonight's check-in with the recertify fix should show up there in a few
hours.  Suggestions for improvement are welcome.)

By the way, is there a way to inspect the certificates of a syntax
object directly?  I'm not sure exactly what I'd do with them, but I'm
sort of thinking I should just ignore (i.e. hide) identifiers that the
client of my program processor can't access rather than blithely
recertifying them all.  But I have no idea how to go about this, or
even whether it makes sense.

--dougo at place.org

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