[plt-scheme] lambda calculus

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Tue Aug 11 08:39:19 EDT 2009

On lambda calculus for computer scientists: don't study the  
logician's version. It's misleading, inappropriate, has generated a  
ton of misunderstandings in computer scientists who don't keep the  
context in mind, and as a result has wasted years and decades in PL  
research. (Some people to this day don't know that LC normal forms  
are nearly entirely irrelevant for the study of PL.)

In sum, the study of LC is only useful for picking up mathematical  
techniques that you need to establish and validate properties of  
languages. The specifics are irrelevant.

-- Matthias

On Aug 11, 2009, at 8:04 AM, emre berat nebioğlu wrote:

> By the way i need to say something.I ask some source to learn  
> lambda calculus,it is true i have an exam but it is not the  
> situation of the original enquirer.Because i have some wish to  
> write functional programming to learn lambda calculus.İ am sorry  
> but i have to meantion.This is not necessary to say ((the situation  
> of the original enquirer) .I aö student who make some computer  
> science.I have a long way but in a day future i become computer  
> scientist !!! Sorry for that mail.
> On Tue, Aug 11, 2009 at 2:23 PM, Matthias Felleisen  
> <matthias at ccs.neu.edu> wrote:
> On Aug 11, 2009, at 2:07 AM, Chris Stephenson wrote:
> (Your student asks general questions, so he's getting general  
> answers.)
> But Barendregt's trick of renaming all bound variables to have  
> different
> names from all free variables simplifies some proofs, but obscures the
> issue of scope for those who interested in Lambda calculus as a model
> for programming languages.
> The phrase you're alluding to has been misunderstood by many many  
> computer scientists. Due to copying it isn't enough to distinguish  
> free/bound variables in the original term. You have to do so at  
> every step of the reduction. Barendregt knows this as the Yellow  
> book shows. Computer science papers seem to not understand this on  
> occasion. So yes, you're right :-) Use de Bruijn indices.
> -- Matthias
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