problem with quoted backslashes

[John W. Eaton]

On 16-Mar-2009, Olaf Till wrote:

| Octave version: 3.0.2
| 
| Please see this:
| 
| octave:1> a = [char("a"), "\\\\   \n"]
| a = a\\   
| 
| octave:2> printf (a)
| a\\   
| 
| and compare with this:
| 
| octave:3> a = [char(97), "\\\\   \n"]
| a = a\\   
| 
| octave:4> printf (a)
| a\   
| octave:5> 

| 
| Note that in both cases variable "a" seems to have the same contents
| according to the first display, but printf (a) behaves differently.
| 
| It was not so with Octave-2.1.73, where the second "printf (a)" also
| yields "a\\", which I would think preferable.

Escape sequences are processed when double-quoted strings (those
inside "") are constructed, but not when single-quoted strings (those
inside '') are constructed.

For compatibility with Matlab, single-quoted strings are special when
they are used as the format argument of {f,s,}printf functions.

For compatibility with Matlab, char(97) produces a single-quoted string.

We had to choose what to do when concatenating single- and
double-quoted strings.  We chose to make them single-quoted strings.

You can get warnings when single- and double- quoted strings are
concatenated by using

  warning on Octave:string-concat

jwe