Re: filesep extension

[Jaroslav Hajek]

On Tue, Nov 11, 2008 at 6:42 PM, Jaroslav Hajek <address@hidden> wrote:
> On Tue, Nov 11, 2008 at 5:31 PM, John W. Eaton <address@hidden> wrote:
>> On 11-Nov-2008, Michael Goffioul wrote:
>>
>> | I noticed a problem in fileparts tests: some tests uses forward slash,
>> | while fileparts uses filesep, which is the backward slash under Windows.
>> | This makes most tests to fail.
>> |
>> | To solve that, I thought about extending filesep behavior and make it
>> | return all file separators when 'all' is given as argument. See the 
>> attached
>> | changeset (OK to apply?). However, now I'd like to modify fileparts.m,
>> | but I'm not sure about the most efficient way to implement find_last_of
>> | functionality in ocave. Any idea?
>>
>> See also this thread:
>>
>>  
>> https://www-old.cae.wisc.edu/pipermail/octave-maintainers/2008-October/009169.html
>>
>> I think your patch is also OK.
>>
>> I'm not sure what to suggest for the best scripting language
>> equivalent for find_last_of.  A regular expression?  That doesn't seem
>> like a great solution and would be a bit messy in the current case
>> because \ is special in a regular expression.  For example, you need
>> something like
>>
>>  regexp ('/foo/bar\baz', '[\\/][^\\/]*$')
>>
>> Do we need a new function, or can someone think of a good way to do
>> this with functions we currently have?
>>
>
> What about implementing this using find (), with similar input &
> output arguments?
>
> Say, like this:
>
> function varargout = strchr (str, chars, varargin)
>  if (nargin < 2 || ! ischar (str) || ! ischar (chars))
>    print_usage ();
>  endif
>  f = false (1, 256);
>  f(chars) = true;
>  varargout = cell (1, nargout);
>  [varargout{:}] = find (reshape (f(str), size (str)), varargin{:});
> endfunction
>
> Two notes:
> 1. I think the function name should start with "str"
> 2. Note that this currently doesn't work with nargout = 0 due to a
> strange indexing bug.
>

Okay so 2 doesn't matter since we always need to call find with at
least one output argument. Also, indexing by char should be shifted by
1, because char is 0..255. The attached version should work:

function varargout = strchr (str, chars, varargin)
  if (nargin < 2 || ! ischar (str) || ! ischar (chars))
    print_usage ();
  endif
  f = false (1, 256);
  f(chars+1) = true;
  varargout = cell (1, nargout){1} = [];
  [varargout{:}] = find (reshape (f(str+1), size (str)), varargin{:});
endfunction


-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz