[Haskell-cafe] Lambda Calculus: Bound and Free formal definitions

Gregg Reynolds dev at mobileink.com
Thu Dec 30 04:40:17 CET 2010

On Wed, Dec 29, 2010 at 9:22 PM, Mark Spezzano <mark.spezzano at chariot.net.au
> wrote:

> Duh, Sorry. Yes, there was a typo
> the second one should read
> If E is a combination E1 E2 then X is bound in E if and only if X is bound
> in E1 or is bound in E2.

Seems odd.  I recommend you always work from at least three different texts.
 Here's Hindley and

"An occurrence of a variable x in a term P is called

   - *bound* if it is in the scope of a \x in P  (NB:  using \ as lambda)
   - *bound and binding* iff it is  the x in \x
   - *free* otherwise"

The tricky question is: bound to what, exactly?

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