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Re: Finding Unused Identifiers


From: Markus Triska
Subject: Re: Finding Unused Identifiers
Date: Thu, 02 Mar 2006 18:18:05 +0100
User-agent: Mozilla Thunderbird 1.0.7 (X11/20051010)

Hi!

B. T. Raven wrote:

> by "unused" do you mean something other than unbound?

I took it to mean "(at least) one write access (set, let, ...), and no read access".

Why can't the file be loaded

Consider:

(let ((a 0))
  (complicated-function) ; not involving a
  (print a))

If "complicated-function" halts, a is (subsequently) used. If it doesn't, a remains unused (the "print" part is never reached). Since whether a Lisp function halts is undecidable, there's no algorithm that always both terminates and correctly identifies all such identifiers in arbitrary programs.

All the best,
Markus.


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