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[CreaPhase.git] / octave_packages / m / strings / findstr.m

diff --git a/octave_packages/m/strings/findstr.m b/octave_packages/m/strings/findstr.m
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+## Copyright (C) 1996-2012 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 3 of the License, 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, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} findstr (@var{s}, @var{t})
+## @deftypefnx {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 true, the returned vector
+## can include overlapping positions (this is the default).  For example:
+##
+## @example
+## @group
+## findstr ("ababab", "a")
+##      @result{} [1, 3, 5];
+## findstr ("abababa", "aba", 0)
+##      @result{} [1, 5]
+## @end group
+## @end example
+##
+## @strong{Caution:} @code{findstr} is scheduled for deprecation.  Use
+## @code{strfind} in all new code.
+## @seealso{strfind, strmatch, strcmp, strncmp, strcmpi, strncmpi, find}
+## @end deftypefn
+
+## Note that this implementation swaps the strings if second one is longer
+## than the first, so try to put the longer one first.
+##
+## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at>
+## Adapted-By: jwe
+
+function v = findstr (s, t, overlap = true)
+
+  if (nargin < 2 || nargin > 3)
+    print_usage ();
+  endif
+
+  if (all (size (s) > 1) || all (size (t) > 1))
+    error ("findstr: arguments must have only one non-singleton dimension");
+  endif
+
+  ## Make S be the longer string.
+  if (length (s) < length (t))
+    [s, t] = deal (t, s);
+  endif
+
+  l_s = length (s);
+  l_t = length (t);
+
+  if (l_t == 0)
+    ## zero length target: return empty set
+    v = [];
+
+  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
+      ## First possible position for next non-overlapping match.
+      next = 1;
+      for idx = 1:length (v)
+        if (v(idx) >= next && s(v(idx) + ind) == t)
+          keep(idx) = 1;
+          ## Skip to the next possible match position.
+          next = v(idx) + l_t;
+        else
+          keep(idx) = 0;
+        endif
+      endfor
+    endif
+    if (! isempty (v))
+      v = v(find (keep));
+    endif
+  endif
+
+  if (isempty (v))
+    v = [];
+  endif
+
+  ## Always return a row vector, because that's what the old one did.
+  if (iscolumn (v))
+    v = v.';
+  endif
+
+endfunction
+
+
+%!assert (findstr ("abababa", "a"), [1, 3, 5, 7])
+%!assert (findstr ("abababa", "aba"), [1, 3, 5]);
+%!assert (findstr ("aba", "abababa", 0), [1, 5]);
+
+%% Test input validation
+%!error findstr ()
+%!error findstr ("foo", "bar", 3, 4);
+%!error findstr (["AB" ; "CD"], "C");
+