The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
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Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#2One of my favorite programming videos: Jim Weirich on the Y Combinator https://www.youtube.com/watch?v=FITJMJjASUs
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#3If there's one thing that the prolific rise of the Y Combinator accelerator has done, it's made the combinator much harder to google for. (Though ofc Fixed-point combinator would still work).
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#4Y Combinator in TXR's embedded Lisp dialect:
@(do
;; The Y combinator:
(defun y (f)
[(op @1 @1)
(op f (op [@@1 @@1]))])
;; The Y-combinator-based factorial:
(defun fac (f)
(do if (zerop @1)
1
(* @1 [f (- @1 1)])))
;; Test: 4! -> 24
(pprinl [[y fac] 4]))Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#5[deleted]
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#6One of my favorite programming videos: Jim Weirich on the Y Combinator https://www.youtube.com/watch?v=FITJMJjASUs
Thanks for letting me discover the work of that man. Its approach to learning about something by actually doing it really shines in the video you linked.
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#7One of my favorite programming videos: Jim Weirich on the Y Combinator https://www.youtube.com/watch?v=FITJMJjASUs
If anyone hasn't seen this I highly recommend it, if not just because Weirich was a great guy and was very entertaining. RIP.
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#8Has the Y combinator been useful to anything? Has it been used in any software in a role other than pedagogic?
It's a beautiful way to make a recursive call without binding the function to an identifier, but has it actually proven useful? It would seem that languages that allow that make it easy to use the Y combinator also typically make it easy to use named recursion with a permanent or a temporary name.
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#9I once tried an insane thing: building the Y-Combinator in C, and wrote a blog post about it. http://kswizz.com/post/50429268286/fibonacci-the-y-combinato...
It was a fun thought exercise. Not something I'd use in production code.
Re: The Y Combinator (no, not that one) – A Crash Course on Lambda Calculus
#10My page on lambda diagrams at
http://www.cwi.nl/~tromp/cl/diagrams.html
has a nice picture of the Y-combinator at the top,
and this note at the bottom:
The diagram in the title, produced by the postscript code below, is a slightly deformed alternative Y diagram made to look like a Y.
%!PS-Adobe-2.0 EPSF-2.0
%%BoundingBox:0 0 118 110
/m{moveto}def/l{lineto}def/c{concat 6 m 0 6 l 7 8 m 0 8 l l l 3 6 l 2 6 m 7 6 l
3 4 m 6 4 l 6 6 l stroke}def 3 0 0 0 1[-8 4 0 8 60 9]c 3 2 0 2 2[-1 1 0 1 0 0]c