[R-SIG-Mac] Unexpected behavior from sprintf()

[Ben Bolker]

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On 12-04-24 04:24 PM, Joran Elias wrote:
> I stumbled across this by accident from this StackOverflow
> question:
> 
> http://stackoverflow.com/q/10300325/324364
> 
> and a subsequent discussion in the StackOverflow R chat room:
> 
> http://chat.stackoverflow.com/transcript/message/3431991#3431991
> 
> The issue is the output from the following code:
> 
> sprintf('%05s',as.character(1:5))
> 
> It appears that when this is run in OS X in either 2.14.2 or
> 2.15.0, the output is:
> 
> [1] "00001" "00002" "00003" "00004" "00005"
> 
> whereas when it is run on other platforms (I saw examples from
> various Windows versions and one user on Ubuntu, all using 2.15.0 I
> believe) you get:
> 
> [1] "    1" "    2" "    3" "    4" "    5"
> 
> There was some uncertainty as to which behavior is "expected". Does
> anyone have any insight into which behavior is "correct" and
> whether this is a bug or not?
> 
> - Joran
> 

  on Ubuntu 10.04 (r-devel):

> sprintf("%05s",1)
[1] "    1"
> sprintf("%05d",1)
[1] "00001"
> 

?sprintf says:

 ‘0’ For numbers, pad to the field width with leading zeros.

"man 3 printf" on Ubuntu 10.04 says:

       0      The  value  should  be  zero padded.  For d, i, o, u, x,
X, a, A, e, E, f, F, g, and G conversions, the converted value is
padded on the left with zeros rather than blanks.  If the 0 and -
flags  both  appear,  the  0  flag  is ignored.   If  a precision is
given with a numeric conversion (d, i, o, u, x, and X), the 0 flag is
ignored.  For other conversions, the behavior is undefined.

  From a lawyerly point of view, ?sprintf is not wrong.  It defines
the behavior for numbers and fails to define it for non-numbers -- so
technically

ZZZZ1

would also be 'correct' (or at least 'not wrong') output for this case.


printstr.c
============================
#include <stdio.h>

int main() {


   printf("%05s\n","1");
}
==========================


under Ubuntu:

gcc printstr.c
printstr.c: In function ‘main’:
printstr.c:6: warning: '0' flag used with ‘%s’ gnu_printf format
bolker at ubuntu-10:~/R/misc$ ./a.out
    1


under OS X:

 gcc printstr.c
printstr.c: In function ‘main’:
printstr.c:6: warning: '0' flag used with ‘%s’ printf format
collywobbles:misc bolker$ ./a.out
00001


  So we do get a compile-time warning in either case.

  Perhaps the R documentation should waffle about platform-specificity
some more ...


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