> On Oct 1, 2016, at 9:29 AM, Jan Kacaba <jan.kac...@gmail.com> wrote:
>
> 2016-10-01 18:02 GMT+02:00 David Winsemius <dwinsem...@comcast.net>:
>>
>>> On Oct 1, 2016, at 8:44 AM, Jan Kacaba <jan.kac...@gmail.com> wrote:
>>>
>>> Hello Dear R-help
>>>
>>> I tried to understand how recursive programming works in R. Bellow is
>>> simple recursive function.
>>>
>>> binary1 <- function(n) {
>>> if(n > 1) {
>>> binary(as.integer(n/2))
>>> }
>>> cat(n %% 2)
>>> }
>>
>> Did you mean to type "binary1(as.integer(n)"?
>
> Yes I meant that.
>
>>> When I call binary1(10) I get 1010. I believe that cat function stores
>>> value to a buffer appending values as recursion proceeds and at the
>>> end it prints the buffer. Am I right?
>>
>> No. Read the ?cat help page. It returns NULL. The material you see at the
>> console is a side-effect.
>>>
>>> I tried to modify the function to get some understanding:
>>>
>>> binary2 <- function(n) {
>>> if(n > 1) {
>>> binary2(as.integer(n/2))
>>> }
>>> cat(n %% 2, sep=",")
>>> }
>>>
>>> With call binary2(10) I get also 1010. Why the output is not separated
>>> by commas?
>>
>> I think because there is nothing to separate when it prints (since there was
>> no "buffer".
>
> If I use function:
> binary3 <- function(n) {
> if(n > 1) {
> binary3(as.integer(n/2))
> }
> cat(n %% 2, ",")
> }
>
> and call binary3(10) the console output is separated. So there must be
> some kind of buffer and also it looks like there is some inconsistency
> in how cat function behaves. Probably there is other explanation.
The only inconsistency is how you sent arguments to cat. In the first instance
you asked cat to display a single character value (and to separate multiple
characters _if_present_ with a comma, .... but there were never any instances
of a cat call with multiple arguments).
In the second instance you told it to display single character values followed
by a comma and it did that 4 times when the argument to the enclosing function
was a decimal 10.
If by buffer you mean the console stream, then I suppose I misunderstood your
use of the term.
--
David Winsemius
Alameda, CA, USA
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