[Haskell-cafe] Slightly off-topic: Lambda calculus

Deniz Dogan deniz.a.m.dogan at gmail.com
Sun Jun 21 13:05:16 EDT 2009

2009/6/21 Andrew Coppin <andrewcoppin at btinternet.com>:
> OK, so I'm guessing there might be one or two (!) people around here who
> know something about the Lambda calculus.
> I've written a simple interpretter that takes any valid Lambda expression
> and performs as many beta reductions as possible. When the input is first
> received, all the variables are renamed to be unique.
> Question: Does this guarantee that the reduction sequence will never contain
> name collisions?
> I have a sinking feeling that it does not. However, I can find no
> counter-example as yet. If somebody here can provide either a proof or a
> counter-example, that would be helpful.

I'm no expert, but it sounds to me like you're doing the equivalent of
"de Bruijn indexing", which is a method to avoid alpha conversion,
which is basically what you're worried about. Therefore, I'm guessing
that there will be no name collisions.

Deniz Dogan

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