From octave-sources-request at bevo dot che dot wisc dot edu  Thu Jul 13 11:19:07 2000
Subject: Re: strncmp, strcmpi, and strncmpi
From: Bill Lash <Bill dot Lash at tellabs dot com>
To: julian at matlinks dot net
CC: octave-sources at bevo dot che dot wisc dot edu, pkienzle@kienzle.powernet.co.uk
Date: Thu, 13 Jul 2000 11:17:59 -0500

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julian at matlinks dot net wrote:
> 
> I did those tests for you in Matlab.  Warning: your implementations are
> _not_ compatible in all cases:

Man am I a bad guesser or what??  These can be easily fixed, I think.
I am attatching new versions.

> 
> "For strncmp and strncmpi, if n<1 I am returning 1 (indicating the
>  strings are equal) as long as s1 and s2 are strings."
> >> nope...
>    strncmp returns 0 if n < 1, no matter what the strings (even nul strings)
>    strncmpi behaves the same way.

ok, fixed that one.

> 
> "For strncmp and strncmpi, if n is greater than both string sizes, I am
>  passing the strings to strcmp without padding to length n.  If s1 and s2
>  are of different length they will automatically cause 0 to be returned
>  even if the difference is only trailing blanks (just like strcmp)."
> >> nope...
>    strncmp returns 0 if n > either string length (even if they have the same
> length)
>    strncmpi behaves the same way.

ok, that was pretty easy to fix as well.

> 
> "For strncmp and strncmpi, if columns(s2) < n <= columns(s1) I am
>  returning 0 (again not padding the short string)."
> >> nope again...
>    strncmp returns 1 if the strings differ in length although the compared
>    substrings match up to n, even with trailing blanks
>    strncmpi behaves the same way.

I think I didn't explain this one very well.  Since you say above that 0
is
always returned if n is greater than either string length,  the
situation that 
I am talking about here would be takne care of by that.

I am attatching a new version of strncmp.m which should fix all of the
problems
that you mention (strncmpi calls strncmp, so there is no need to change
strncmpi)

Thanks for the input.

Bill Lash
lash at tellabs dot com
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## Copyright (C) 2000 Bill Lash
##
## This program is free software and may be used for any purpose.  This
## copyright notice must be maintained.  Bill Lash is not responsible
## for the consequences of using this software.

## usage: strncmp (s1, s2, n)
##
## Compare the first n characters of two strings, returning 1 if
## they are the same, and 0 otherwise.
##
## Note: For compatibility with Matlab, Octave's strncmp function
## returns 1 if the strings are equal, and 0 otherwise.  This is
## just the opposite of the corresponding C library function.

## Author: Bill Lash (lash at tellabs dot com)


function status = strncmp(s1, s2, n)

  if (nargin != 3)
    usage ("strncmp (s, t, n)");
  endif

  status = 0;		# Assume strings are different
  if (isstr (s1) && isstr(s2))
    c1 = columns (s1);
    c2 = columns (s2);
    if (n < 1)		
			# Comparing less than 1 character of the string
      status = 0;	# will always say they are not equal (for Matlab
		        # compatibility

    elseif ((n <= c1) && (n <= c2))
       status = strcmp(s1(:,1:n),s2(:,1:n));
    else 
       status = 0;
    endif
  endif

endfunction

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