## 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. ## -*- texinfo -*- ## @deftypefn {Function File} {} findstr (@var{s}, @var{t}, @var{overlap}) ## Return the vector of all positions in the longer of the two strings ## @var{s} and @var{t} where an occurrence of the shorter of the two starts. ## If the optional argument @var{overlap} is nonzero, the returned vector ## can include overlapping positions (this is the default). For example, ## ## @example ## findstr ("ababab", "a") ## @result{} [ 1, 3, 5 ] ## findstr ("abababa", "aba", 0) ## @result{} [ 1, 5 ] ## @end example ## @end deftypefn ## ## Note that this implementation swaps the strings if second on is longer ## than the first, so try to put the longer one first. ## ## Author: Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> ## Adapted-By: jwe ## Paul Kienzle <pkienzle@kienzle.powernet.co.uk> ## vectorize for speed function v = findstr (s, t, overlap) if (nargin < 2 || nargin > 3) usage ("findstr (s, t, overlap)"); endif if (!isstr (s) || !isstr (t) || all (size (s) > 1) || all (size (t) > 1) ) error ("findstr: expecting first two arguments to be strings"); endif if (nargin == 2) overlap = 1; endif ## Make S be the longer string. if (length (s) < length (t)) tmp = s; s = t; t = tmp; endif l_s = length (s); l_t = length (t); if ( l_t == 0 ) ## zero length target: return all indices v = 1 : l_s; elseif ( l_t == 1 ) ## length one target: simple find v = find (s==t); elseif ( l_t == 2 ) ## length two target: find first at i and second at i+1 v = find (s (1 : l_s-1) == t (1) & s (2 : l_s) == t (2)); else ## length three or more: match the first three by find then go through ## the much smaller list to determine which of them are real matches limit = l_s - l_t + 1; v = find (s (1 : limit) == t(1) & s (2 : limit+1) == t (2) & s (3 : limit+2) == t(3) ); endif ## Need to search the index vector if our find was too short ## (target length > 3), or if we don't allow overlaps. Note though ## that there cannot be any overlaps if the first character in the ## target is different from the remaining characters in the target, ## so a single character, two different characters, or first character ## different from the second two don't need to be searched. if ( l_t >= 3 || ( !overlap && l_t > 1 && any (t(1) == t(2:l_t)) ) ) ## force strings to be both row vectors or both column vectors if (all (size (s) != size (t))) t = t.'; endif ## determine which ones to keep keep = zeros(size(v)); ind = 0:l_t-1; if ( overlap ) for idx = 1:length(v) keep(idx) = all (s (v(idx) + ind) == t); endfor else next = 1; # first possible position for next non-overlapping match for idx = 1:length(v) if (v (idx) >= next && s (v (idx) + ind) == t) keep(idx) = 1; next = v(idx) + l_t; # skip to the next possible match position else keep(idx) = 0; endif endfor endif if (!isempty(v)) v = v(find(keep)); endif endif ## Always return a column vector, because that's what the old one did if (rows (v) > 1) v = v.'; endif endfunction

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