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PG on the cover of Forbes

forbes.com

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Re: PG on the cover of Forbes

#41

Post by eru »

meastham wrote: post #25
evanrmurphy wrote: post #18

Earlier quoted context omitted.

> Heh... completely wrong, but I suppose it's the best you can expect a non-techie/math nerd readership to get. Heck, it's probably close to the most you can expect the average programmer to get. How would you explain the Y Combinator to the Hacker News readership?

Like others have mentioned it's rather academic, but also pretty cool. It's a way of introducing recursive functions into the untyped lambda calculus. I think the easiest way to see it is using it in scheme to define an anonymous recursive function: (((lambda (fact) ((lambda (f) (fact (lambda (n) ((f f) n)))) (lambda (f) (fact (lambda (n) ((f f) n)))))) (lambda (fact) (lambda (n) (if (= n 0) 1 (* n (fact (- n 1))))))…

You can even get rid of the lambdas, with SKI calculus. (And the I in SKI calculus is also unnecessary.)

Re: PG on the cover of Forbes

#42

Post by abstractbill »

axod wrote: post #38
spacemanaki wrote: post #35

Earlier quoted context omitted.

The "meat" of it is really that (Y F) = (F (Y F)). In other words Y applied to a function F expands to F applied the original expression, so it builds up nested calls of F. I can't do it justice, but it's definitely much more interesting and even beautiful than "meh". I guess there are always "practical" vs "academic" arguments to be made but I find stuff like the lambda calculus, Y, Church numerals, all really cool.

Yeah ok, it's sort of interesting as a curiosity. But it's going to be terribly inefficient if used, and doesn't really have any practical application. I've always been more of a practical "why not just use a loop" kinda guy, so it's probably wasted on me.

Right, it's not really supposed to be used, but it's impressive and interesting in the same way that e^πi = -1 is.

Re: PG on the cover of Forbes

#43

Post by eru »

simplegeek wrote: post #23
axod wrote: post #22

Earlier quoted context omitted.

afaik it's pretty academic. The only practical application is to allow recursion in languages that don't do recursion which is pretty much none. This is a good description if you're into that sort of thing: http://mvanier.livejournal.com/2897.html The meat of it is that you can 'do' recursion by building up functions that call other functions :/ meh

>> The only practical application is to allow recursion in languages that don't do recursion which is pretty much none. Above is a very hard sentence to parse for non-native speakers, just saying ;)

I did not have too hard a time. But the sentence is not a model of clarity.

Re: PG on the cover of Forbes

#44

Post by eru »

axod wrote: post #38
spacemanaki wrote: post #35

Earlier quoted context omitted.

The "meat" of it is really that (Y F) = (F (Y F)). In other words Y applied to a function F expands to F applied the original expression, so it builds up nested calls of F. I can't do it justice, but it's definitely much more interesting and even beautiful than "meh". I guess there are always "practical" vs "academic" arguments to be made but I find stuff like the lambda calculus, Y, Church numerals, all really cool.

Yeah ok, it's sort of interesting as a curiosity. But it's going to be terribly inefficient if used, and doesn't really have any practical application. I've always been more of a practical "why not just use a loop" kinda guy, so it's probably wasted on me.

Loops are just a special case of recursion, and only necessary for languages that don't support recursion very well. As an example, Scheme and Haskell have no use for loops.

Re: PG on the cover of Forbes

#46

Post by meese_ »

evanrmurphy wrote: post #18
j_baker wrote: post #2

"Y Combinator--a computer term for a program that runs other programs" Heh... completely wrong, but I suppose it's the best you can expect a non-techie/math nerd readership to get. Heck, it's probably close to the most you can expect the average programmer to get. EDIT: And another one... "Graham met Morris, an authority on the Unix computer language"

> Heh... completely wrong, but I suppose it's the best you can expect a non-techie/math nerd readership to get. Heck, it's probably close to the most you can expect the average programmer to get. How would you explain the Y Combinator to the Hacker News readership?

http://lambdawesome.com

Re: PG on the cover of Forbes

#47

Post by dfranke »

gojomo wrote: post #8
chaosmachine wrote: post #3

Here is the actual cover: http://imgur.com/gOyI9.jpg

A nice, striking (against the red), somewhat atypical picture of PG. Did the photographer coach to suppress the usual smile?

What struck me in that photo is that he looks a bit older than he is. Which, for Forbes' audience, I suspect is deliberate.

Re: PG on the cover of Forbes

#48

Post by axod »

eru wrote: post #44
axod wrote: post #38

Earlier quoted context omitted.

Yeah ok, it's sort of interesting as a curiosity. But it's going to be terribly inefficient if used, and doesn't really have any practical application. I've always been more of a practical "why not just use a loop" kinda guy, so it's probably wasted on me.

Loops are just a special case of recursion, and only necessary for languages that don't support recursion very well. As an example, Scheme and Haskell have no use for loops.

Loops are how most people think. They're also how most CPUs think.

It seems to me logical for both parties to express programs mostly using loops.

Re: PG on the cover of Forbes

#49

Post by axod »

abstractbill wrote: post #42
axod wrote: post #38

Earlier quoted context omitted.

Yeah ok, it's sort of interesting as a curiosity. But it's going to be terribly inefficient if used, and doesn't really have any practical application. I've always been more of a practical "why not just use a loop" kinda guy, so it's probably wasted on me.

Right, it's not really supposed to be used, but it's impressive and interesting in the same way that e^πi = -1 is.

I didn't really find that. It's just functions calling other functions. How exciting can that get :/

Re: PG on the cover of Forbes

#50

Post by axod »

eru wrote: post #43
simplegeek wrote: post #23

Earlier quoted context omitted.

>> The only practical application is to allow recursion in languages that don't do recursion which is pretty much none. Above is a very hard sentence to parse for non-native speakers, just saying ;)

I did not have too hard a time. But the sentence is not a model of clarity.

... such is my brain.
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