### Copyright (C) 1996 Kurt Hornik
### 
### 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, 59 Temple Place - Suite 330, Boston, MA
### 02111-1307, USA.

## usage:  index (s, t)
##
## Returns the position of the first occurence of the string T in the
## string S or 0 if no occurence is found.
##
## NOTE: this function does not work for arrays of strings.

function n = index (s, t)

  ## This is patterned after the AWK function of the same name.

  ## Original version by Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at>.

  if (nargin != 2)
    usage ("index (s, t)");
  endif

  n = 0;

  if (isstr (s) && isstr (t))

    l_s = length (s);
    l_t = length (t);

    if (l_t <= l_s)
      tmp = l_s - l_t + 1;
      for idx = 1 : tmp
	if (strcmp (substr (s, idx, l_t), t))
	  n = idx;
	  return;
	endif
      endfor
    endif

  else
    error ("index: expecting string arguments");
  endif
  
endfunction