# [R] Break during the recursion?

Atte Tenkanen attenka at utu.fi
Sun Jul 15 17:36:56 CEST 2007

```> On 15/07/2007 10:33 AM, Atte Tenkanen wrote:
> >> On 15/07/2007 10:06 AM, Atte Tenkanen wrote:
> >>> Hi,
> >>>
> >>> Is it possible to break using if-condition during the recursive
> >> function?
> >> You can do
> >>
> >>  if (condition) return(value)
> >>
> >>> Here is a function which almost works. It is for inorder-tree-
> >> walk.
> >>> iotw<-function(v,i,Stack,Indexes) # input: a vector and the
> first
> >> index (1), Stack=c(), Indexes=c().
> >>> {
> >>> 	print(Indexes)
> >>> 	# if (sum(i)==0) break # Doesn't work...
> >> 	if (sum(i)==0) return(NULL)
> >>
> >> should work.
> >>
> >> Duncan Murdoch
> >
> > Hmm - - - I'd like to save the Indexes-vector (in the example
> c(8,4,9,2,10,5,11,1,3)) and stop, when it is ready.
>
> This seems more like a problem with the design of your function
> than a
> description of the problem doesn't make sense to me.  What does it
> mean
> to do an inorder tree walk on something that isn't a tree?
>
> Duncan Murdoch

The symbols in vector v have been originally derived from "tree". See

http://users.utu.fi/attenka/Tree.jpg

But perhaps there's another way to do this, for instance by using loops and if-conditions?

Atte

>
>
> >
> > The results are enclosed to the end.
> >
> > Atte
> >
> >>>
> >>> 	if (is.na(v[i])==FALSE & is.null(unlist(v[i]))==FALSE)
> >>>         	{Stack=c(i,Stack); i=2*i; iotw(v,i,Stack,Indexes)}
> >>> 	Indexes=c(Indexes,Stack[1])
> >>> 	Stack=pop.stack(Stack)\$vector
> >>> 	Indexes=c(Indexes,Stack[1])
> >>> 	i=2*Stack[1]+1
> >>> 	Stack=pop.stack(Stack)\$vector
> >>> 	iotw(v,i,Stack,Indexes)
> >>> }
> >>>
> >>>
> >>>> v=c(`-`,`+`,1,`^`,`^`,NA,NA,"X",3,"X",2)
> >>>> Stack=c()
> >>>> Indexes=c()
> >>>> iotw(v,1,Stack,Indexes)
> >>> NULL
> >>> NULL
> >>> NULL
> >>> NULL
> >>> NULL
> >>> [1] 8 4
> >>> [1] 8 4
> >>> [1] 8 4 9 2
> >>> [1] 8 4 9 2
> >>> [1] 8 4 9 2
> >>> [1]  8  4  9  2 10  5
> >>> [1]  8  4  9  2 10  5
> >>> [1]  8  4  9  2 10  5 11  1
> >>> [1]  8  4  9  2 10  5 11  1
> >>> [1]  8  4  9  2 10  5 11  1  3
> >>> Error in if (is.na(v[i]) == FALSE & is.null(unlist(v[i])) ==
> >> FALSE) { :
> >>> 	argument is of length zero
> >>>
> >>> Regards,
> >>>
> >>> Atte Tenkanen
> >>> University of Turku, Finland
> >>>
> >
> >
> >> iotw(v,1,Stack,Indexes)
> > NULL
> > NULL
> > NULL
> > NULL
> > NULL
> > [1] 8 4
> > [1] 8 4
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4
> > [1] 8 4
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1] 8 4 9 2
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1
> > [1]  8  4  9  2 10  5 11  1  3
> > [1]  8  4  9  2 10  5 11  1  3
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1
> > [1] 8 4 9 2 5 1 3
> > [1] 8 4 9 2 5 1 3
> > [1] 4 2
> > [1] 4 2
> > [1] 4 2
> > [1]  4  2 10  5
> > [1]  4  2 10  5
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5
> > [1]  4  2 10  5
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1
> > [1]  4  2 10  5 11  1  3
> > [1]  4  2 10  5 11  1  3
> > [1] 4 2 5 1
> > [1] 4 2 5 1
> > [1] 4 2 5 1 3
> > [1] 4 2 5 1 3
> > [1] 2 1
> > [1] 2 1
> > [1] 2 1 3
> > [1] 2 1 3
> > [1] 1
> > [1] 1
>
>

```