[plt-scheme] DrScheme: highlight free variables within selected expression?

From: Robby Findler (robby at cs.uchicago.edu)
Date: Thu Jul 5 13:17:15 EDT 2007

There's a lot of things we could do (like the below) if we had
on-the-fly macro expansion, but we don't yet, I'm sorry to say.


On 7/5/07, Ryan Newton <newton at mit.edu> wrote:
> Seeing as there was just a long thread on colorizing parentheses, I
> thought I'd take this opportunity to mention a UI feature that I
> would personally find much more useful than multicolored parens.
>     Namely, highlighting free variables within a selected expression.
> DrScheme already does this at a module granularity -- distinguishing
> locally bound identifiers from those imported from other modules.
> But because I use DrScheme frequently for factoring existing code, I
> often want to pick up a (large) expression and move it somewhere
> else.  Well, after I've moved it, DrScheme will happily inform me of
> unbound identifiers, which is great.  But it would be even better if
> I could immediately see the free variables within a highlighted
> expression.  (Without hovering the mouse over each identifier!)
> -Ryan
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