Talk:Sudan function

Please check wether the definition is good. My source isn't a very reliable one (random google search, namely ). I hope it's ok, however--it looks enough similarly to the Ackermann function to me to think it grows fast, as it should.

Is the table of values right?

I have an assignment for entry level Computer Science which is to implement the Sudan function recursively. I was trying to find some sample values to see if I had implemented it correctly, so I came to the wikipedia article. My program was not working- or so I thought. The table in the article is correct if you change the third condition's second argument to F(x, y) + y-----leaving out the plus 1. Can anyone more skilled speak to this?

137.54.8.99 (talk) 21:38, 15 March 2010 (UTC)

Follow up- I read it wrong. Article is right.

137.54.8.99 (talk) 21:43, 15 March 2010 (UTC)

What is exactly the Sudan function ?

The article does not say what the Sudan function exactly is, as it defines a sequence $(F_{n})_{n\geq 0}$ of functions.

Perhaps it should be more appropriate to write the function $F(n,x,y)$ whith three arguments. Pierre de Lyon 11:49, 19 May 2006 (UTC)

Would that make the definition:

$F(0,x,y)=x+y,\,$

$F(n+1,x,0)=x,\ n\geq 0\,$

$F(n+1,x,y+1)=F(n,F(n+1,x,y),F(n+1,x,y)+y+1),\ n\geq 0.\,$

or shortened:

$F(0,x,y)=x+y,\,$

$F(n,x,0)=x,\ n\geq 1\,$

$F(n,x,y)=F(n-1,F(n,x,y-1),F(n,x,y-1)+y),\ n\geq 1.\,$

? - ℚuackor 20:02, 25 September 2007 (UTC)

This is exactly what I meant. By the way, I prefer the first definition which refers more to its inductive definition and makes a difference between the cases $0$ and $n+1$. Pierre de Lyon 17:37, 30 October 2007 (UTC)

The function here doesn't match Sudan's paper

I checked both the 1979 article and the 1927 paper, and both of them describe Sudan's function as a function that uses transfinite recursion as follows:

$\psi (a,b,0)=a+b$

$\psi (a,b,n+1)=t_{c}(a,\lambda _{m}\psi (c,m,n),b)$

where

$t_{c}(a,f(c),0)=a$

$t_{c}(a,f(c),n+1)=f(t_{c}(a,f(c),n+1))$.

I don't understand the functions in the paper well enough at the moment to interpret them. The source linked above attributes the function as given to MR 82k:03061 but I can't interpret this identifier. Arcorann (talk) 09:30, 1 May 2020 (UTC)