From bug-request at octave dot org Fri May 20 14:46:08 2005
Subject: Re: strcmp doesn't return a bool
From: Tom Holroyd <tomh at kurage dot nimh dot nih dot gov>
To: Tom Holroyd <tomh at kurage dot nimh dot nih dot gov>
CC: bug at octave dot org, "John W. Eaton" <jwe@bevo.che.wisc.edu>,         octave-dev@lists.sourceforge.net
Date: Fri, 20 May 2005 15:44:56 -0400

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Tom Holroyd wrote:
> The strncmp implementation in octave-forge doesn't handle cell arrays at
> all.

Here's one that does.  This is based on JWE's strcmp.

I collapsed the case
	strncmp(cell array, string matrix, n)
to
	strncmp(string matrix, cell array, n)
with the arguments reversed; the same thing could be done to strcmp.  I don't 
know if it's slower or faster, but it's easier to maintain, certainly.  There's 
a similar possible collapse in the cell, cell case, but it looks like it might 
be a bit slower.  I didn't time it, it just looks that way.  That one's minor 
anyway.

Of course these are both popular functions and as one person has already 
mentioned today are good candidates for builtins.  These guys are both different 
from C's str*cmp, so at least, the builtin can follow the logic here, which is 
compatible and correct, as far as I know.
-- 
Dr. Tom Holroyd
"A man of genius makes no mistakes. His errors are volitional and
are the portals of discovery." -- James Joyce

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 name="strncmp.m"
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 filename="strncmp.m"

## Copyright (C) 1996, 1997 John W. Eaton
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, write to the Free
## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301, USA.

## -*- texinfo -*-
##  at deftypefn {Function File} {} strncmp (@var{s1}, @var{s2}, @var{n})
## Compares the first n characters (columns) of two strings, returning 1 if
## they are the same, and 0 otherwise.
##
##  at strong{Caution:} For compatibility with @sc{Matlab}, Octave's strcmp
## function returns 1 if the strings are equal, and 0 otherwise. This is
## just the opposite of the corresponding C library function.
##  at end deftypefn

## Author: jwe
## Adapted from strcmp.m by Tom Holroyd <tomh at kurage dot nimh dot nih dot gov>

function retval = strncmp (s1, s2, n)

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

  retval = 0;

  if (isstr (s1))
    [r1, c1] = size (s1);
    if (isstr (s2))
      [r2, c2] = size (s2);
      if (r1 == r2 && c1 == c2)
	if (c1 == 0)
	  retval = 1;
	else
	  if (c1 > n)
	    t1 = s1(:, 1:n);
	    t2 = s2(:, 1:n);
	    retval = all (all (t1 == t2));
	  else
	    retval = all (all (s1 == s2));
	  endif
	endif
      elseif (r1 == r2)
	if (r1 == 0)
	  retval = 1;
	else
	  l1 = min(n, c1);
	  l2 = min(n, c2);
	  if (l1 == l2)
	    t1 = s1(:, 1:l1);
	    t2 = s2(:, 1:l2);
	    retval = all (all (t1 == t2));
	  endif
	endif
      endif
    elseif (iscellstr (s2))
      [r2, c2] = size (s2);
      if (r1 == 1)
	t2 = s2(:);
	m = length (t2);
	retval = zeros (m, 1);
	for i = 1:m
	  retval(i) = strncmp (s1, t2{i}, n);
	endfor
	retval = reshape (retval, r2, c2);
      elseif (r1 > 1)
	if (r2 == 1 && c2 == 1)
	  t2 = s2{1};
	  retval = zeros (r1, 1);
	  for i = 1:r1
	    retval(i) = strncmp (deblank (s1(i,:)), t2, n);
	  endfor
	else
	  t2 = s2(:);
	  m = length (t2);
	  if (m == r1)
	    retval = zeros (m, 1);
	    for i = 1:m
	      retval(i) = strncmp (deblank (s1(i,:)), t2{i}, n);
	    endfor
	    retval = reshape (retval, r2, c2);
	  else
	    error ("strncmp: nonconformant arrays");
	  endif
	endif
      endif
    endif
  elseif (iscellstr (s1))
    [r1, c1] = size (s1);
    if (isstr (s2))
      retval = strncmp(s2, s1, n);
    elseif (iscellstr (s2))
      [r2, c2] = size (s2);
      if (r1 == 1 && c1 == 1)
	t1 = s1{:};
	t2 = s2(:);
	m = length (t2);
	retval = zeros (m, 1);
	for i = 1:m
	  retval(i) = strncmp (t1, t2{i}, n);
	endfor
	retval = reshape (retval, r2, c2);
      elseif (r2 == 1 && c2 == 1)
	# retval = strncmp(s2, s1, n);
	t1 = s1(:);
	t2 = s2{:};
	m = length (t1);
	retval = zeros (m, 1);
	for i = 1:m
	  retval(i) = strncmp (t1{i}, t2, n);
	endfor
	retval = reshape (retval, r1, c1);
      elseif (r1 == r2 && c1 == c2)
	t1 = s1(:);
	t2 = s2(:);
	m = length (t1);
	for i = 1:m
	  retval(i) = strncmp (t1{i}, t2{i}, n);
	endfor
	retval = reshape (retval, r1, c1);
      else
	error ("strncmp: nonconformant cell arrays");
      endif
    endif
  endif

  if (n < 1)
    retval = zeros(size(retval));
  endif

  retval = retval == 1;
endfunction

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