# [R] Break during the recursion?

Atte Tenkanen attenka at utu.fi
Sun Jul 15 16:33:13 CEST 2007

```> 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.

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

```