R devel - Aug 2016 - seq.int does not return a sequence of integers sometimes

I have a script that goes wrong because I assumed that seq.int would
return integers.

Below please see it does not unless user is super cautious about
inserting "L" with inputs. I think seq.int should do coercion for me
before returning the sequence.
> xx <- seq.int(1,10)
> class(xx)
[1] "integer"
> is.integer(xx)
[1] TRUE
> xx <- seq.int(1,10, 2)
> class(xx)
[1] "numeric"
> is.integer(xx)
[1] FALSE
> xx <- seq.int(1,10, 2L)
> class(xx)
[1] "numeric"
> is.integer(xx)
[1] FALSE
> xx <- seq.int(1L, 10L, 2L)
> class(xx)
[1] "integer"
> is.integer(xx)
[1] TRUE


I think all of those should have same return value, if the function is
correctly named seq.int.

-- 
Paul E. Johnson   http://pj.freefaculty.org
Director, Center for Research Methods and Data Analysis http://crmda.ku.edu

I only use this account for email list memberships. To write directly,
address me at pauljohn at ku.edu.

> On Aug 3, 2016, at 3:12 PM, Paul Johnson <pauljohn32 at gmail.com>
wrote:
> 
> I have a script that goes wrong because I assumed that seq.int would
> return integers.
> 
> Below please see it does not unless user is super cautious about
> inserting "L" with inputs. I think seq.int should do coercion for
me
> before returning the sequence.
> 
>> xx <- seq.int(1,10)
>> class(xx)
> [1] "integer"
>> is.integer(xx)
> [1] TRUE
>> xx <- seq.int(1,10, 2)
>> class(xx)
> [1] "numeric"
>> is.integer(xx)
> [1] FALSE
>> xx <- seq.int(1,10, 2L)
>> class(xx)
> [1] "numeric"
>> is.integer(xx)
> [1] FALSE
>> xx <- seq.int(1L, 10L, 2L)
>> class(xx)
> [1] "integer"
>> is.integer(xx)
> [1] TRUE
> 
> 
> I think all of those should have same return value, if the function is
> correctly named seq.int.

Paul,

?seq.int has the following:

under Details:

"seq.int is an internal generic which dispatches on methods for
"seq" based on the class of the first supplied argument (before
argument matching)."

and under Value:

"seq.int and the default method of seq for numeric arguments return a
vector of type "integer" or "double": programmers should not
rely on which."


So:
> is.integer(1)
[1] FALSE
> is.integer(1L)
[1] TRUE

which would seem to explain the behavior that you are observing.

Regards,

Marc Schwartz

On 03/08/2016 4:12 PM, Paul Johnson wrote:
> I have a script that goes wrong because I assumed that seq.int would
> return integers.
"int" means "internal", not "integer".  Sometimes
you should read the
documentation.

Duncan Murdoch
>
> Below please see it does not unless user is super cautious about
> inserting "L" with inputs. I think seq.int should do coercion for
me
> before returning the sequence.
>
>> xx <- seq.int(1,10)
>> class(xx)
> [1] "integer"
>> is.integer(xx)
> [1] TRUE
>> xx <- seq.int(1,10, 2)
>> class(xx)
> [1] "numeric"
>> is.integer(xx)
> [1] FALSE
>> xx <- seq.int(1,10, 2L)
>> class(xx)
> [1] "numeric"
>> is.integer(xx)
> [1] FALSE
>> xx <- seq.int(1L, 10L, 2L)
>> class(xx)
> [1] "integer"
>> is.integer(xx)
> [1] TRUE
>
>
> I think all of those should have same return value, if the function is
> correctly named seq.int.
>