Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Lisp is not based on the Lambda Calculus

danielsz.github.io

Post reply on HN
Print view View original

11–20 of 138 posts

Re: Lisp is not based on the Lambda Calculus

#11

Post by illvm »

vga805 wrote: post #3

The post quotes McCarthy: "one of the myths concerning LISP that people think up or invent for themselves becomes apparent, and that is that LISP is somehow a realization of the lambda calculus, or that was the intention. The truth is that I didn't understand the lambda calculus, really" - John McCarthy So there are a two issues here, 1) whether or not it was McCarthy's intention to realize the Lambda Calculus in LIS…

Could it be that, at least some, university teach programming languages with the idea that Lisp has this feature? My PL course at Northeastern had SHLAC (Scheme Has Lambda Calculus) where we started with an identity function and built up from there.

Re: Lisp is not based on the Lambda Calculus

#13

Post by Shebanator »

tudelo wrote: post #6
jasim wrote: post #2

If I understood you right, Lisp was not directly inspired by lambda calculus, but from McCarthy's own research into recursive functions where he found that the three primary functions can cover the whole of computation. What I'm extrapolating from this is that McCarthy's ideas are similar in implication to Lambda Calculus where you can define computation with just function abstraction and application, and use Peano n…

What "three primary functions" are you referring to?

This is touched on in the article:

"They are interesting because with just three initial functions (successor, constant and projection functions) closed under composition and primitive recursion, one can produce most computable functions studied in number theory (addition, division, factorial, exponential, etc.)."

Re: Lisp is not based on the Lambda Calculus

#14

Post by pwpwp »

One of the newest Lisp dialects, Kernel, is pretty close to lambda calculus, though. Like in LC, there is no implicit evaluation of arguments. A fexpr receives the "source code" of its input expressions, similar to LC. Then it can explicitly evaluate those it cares about.

https://web.cs.wpi.edu/~jshutt/kernel.html

Re: Lisp is not based on the Lambda Calculus

#15

Post by vga805 »

illvm wrote: post #11
vga805 wrote: post #3

The post quotes McCarthy: "one of the myths concerning LISP that people think up or invent for themselves becomes apparent, and that is that LISP is somehow a realization of the lambda calculus, or that was the intention. The truth is that I didn't understand the lambda calculus, really" - John McCarthy So there are a two issues here, 1) whether or not it was McCarthy's intention to realize the Lambda Calculus in LIS…

Could it be that, at least some, university teach programming languages with the idea that Lisp has this feature? My PL course at Northeastern had SHLAC (Scheme Has Lambda Calculus) where we started with an identity function and built up from there.

That seems likely. But then, I would think LISP does realize the lambda calculus in some sense. It naturally lends itself to this sort of exercise and it's really successful.

Re: Lisp is not based on the Lambda Calculus

#16

Post by waitwhatwhere »

Interesting parallel with stories out there where authors think teachers get their writings “wrong”.

Unintended metaphor and application are things.

Smacks of a cognitive bias known as functional fixedness: https://en.m.wikipedia.org/wiki/Functional_fixedness

A screwdriver can also be a pry bar :-)

Imo this is why looser IP laws are important. Humanity needs to be able to rethink and find new application of its epistemological ideas to find new ideas of interest.

Too often we’re held to thinking about IP only the way the author intended. It’s almost pushing into thought policing.

Re: Lisp is not based on the Lambda Calculus

#17

Post by ayushgp »

tudelo wrote: post #6
jasim wrote: post #2

If I understood you right, Lisp was not directly inspired by lambda calculus, but from McCarthy's own research into recursive functions where he found that the three primary functions can cover the whole of computation. What I'm extrapolating from this is that McCarthy's ideas are similar in implication to Lambda Calculus where you can define computation with just function abstraction and application, and use Peano n…

What "three primary functions" are you referring to?

I suggest you to watch this video if you want to understand how 3 basic functions can be used to create whole language https://youtu.be/3VQ382QG-y4

Re: Lisp is not based on the Lambda Calculus

#18

Post by commandlinefan »

QuercusMax wrote: post #9
leshow wrote: post #5

Stupid question, why is it often written "_the_ lambda calculus" and not just "lambda calculus"

Probably for the same reason that some people refer to regular calculus as "the calculus".

You'll always sound smart if you remember that "maths" is plural and one of them is "the calculus".

Re: Lisp is not based on the Lambda Calculus

#19

Post by agumonkey »

vga805 wrote: post #3

The post quotes McCarthy: "one of the myths concerning LISP that people think up or invent for themselves becomes apparent, and that is that LISP is somehow a realization of the lambda calculus, or that was the intention. The truth is that I didn't understand the lambda calculus, really" - John McCarthy So there are a two issues here, 1) whether or not it was McCarthy's intention to realize the Lambda Calculus in LIS…

both fair points but I'd like to know if he mentioned why on earth did he pick lambda. lambda expressions/closures turned out to be a very peculiar and important path.

Re: Lisp is not based on the Lambda Calculus

#20

Post by leadingthenet »

commandlinefan wrote: post #18
QuercusMax wrote: post #9

Earlier quoted context omitted.

Probably for the same reason that some people refer to regular calculus as "the calculus".

You'll always sound smart if you remember that "maths" is plural and one of them is "the calculus".

Maths is the common spelling and pronunciation in standard British English, though.
Post reply on HN