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1 ## Copyright (C) 1996 Kurt Hornik |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} findstr (@var{s}, @var{t}, @var{overlap}) |
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22 ## Return the vector of all positions in the longer of the two strings |
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23 ## @var{s} and @var{t} where an occurrence of the shorter of the two starts. |
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24 ## If the optional argument @var{overlap} is nonzero, the returned vector |
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25 ## can include overlapping positions (this is the default). For example, |
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26 ## |
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27 ## @example |
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28 ## findstr ("ababab", "a") |
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29 ## @result{} [ 1, 3, 5 ] |
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30 ## findstr ("abababa", "aba", 0) |
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31 ## @result{} [ 1, 5 ] |
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32 ## @end example |
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33 ## @end deftypefn |
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34 |
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35 ## Note that this implementation swaps the strings if second one is longer |
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36 ## than the first, so try to put the longer one first. |
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37 ## |
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38 ## Author: Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> |
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39 ## Adapted-By: jwe |
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40 |
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41 function v = findstr (s, t, overlap) |
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42 |
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43 if (nargin < 2 || nargin > 3) |
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44 usage ("findstr (s, t, overlap)"); |
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45 endif |
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46 |
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47 if (! isstr (s) || ! isstr (t) || all (size (s) > 1) || all (size (t) > 1)) |
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48 error ("findstr: expecting first two arguments to be strings"); |
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49 endif |
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50 |
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51 if (nargin == 2) |
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52 overlap = 1; |
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53 endif |
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54 |
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55 ## Make S be the longer string. |
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56 if (length (s) < length (t)) |
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57 tmp = s; |
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58 s = t; |
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59 t = tmp; |
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60 endif |
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61 |
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62 l_s = length (s); |
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63 l_t = length (t); |
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64 |
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65 if (l_t == 0) |
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66 ## zero length target: return empty set |
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67 v = []; |
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68 |
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69 elseif (l_t == 1) |
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70 ## length one target: simple find |
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71 v = find (s == t); |
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72 |
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73 elseif (l_t == 2) |
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74 ## length two target: find first at i and second at i+1 |
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75 v = find (s(1:l_s-1) == t(1) & s(2:l_s) == t(2)); |
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76 |
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77 else |
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78 ## length three or more: match the first three by find then go through |
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79 ## the much smaller list to determine which of them are real matches |
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80 limit = l_s - l_t + 1; |
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81 v = find (s(1:limit) == t(1) |
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82 & s(2:limit+1) == t(2) |
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83 & s (3:limit+2) == t(3)); |
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84 endif |
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85 |
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86 ## Need to search the index vector if our find was too short |
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87 ## (target length > 3), or if we don't allow overlaps. Note though |
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88 ## that there cannot be any overlaps if the first character in the |
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89 ## target is different from the remaining characters in the target, |
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90 ## so a single character, two different characters, or first character |
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91 ## different from the second two don't need to be searched. |
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92 if (l_t >= 3 || (! overlap && l_t > 1 && any (t(1) == t(2:l_t)))) |
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93 ## force strings to be both row vectors or both column vectors |
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94 if (all (size (s) != size (t))) |
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95 t = t.'; |
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96 endif |
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97 |
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98 ## determine which ones to keep |
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99 keep = zeros (size (v)); |
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100 ind = 0:l_t-1; |
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101 if (overlap) |
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102 for idx = 1:length (v) |
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103 keep(idx) = all (s(v(idx) + ind) == t); |
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104 endfor |
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105 else |
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106 next = 1; # first possible position for next non-overlapping match |
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107 for idx = 1:length (v) |
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108 if (v(idx) >= next && s(v(idx) + ind) == t) |
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109 keep(idx) = 1; |
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110 next = v(idx) + l_t; # skip to the next possible match position |
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111 else |
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112 keep(idx) = 0; |
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113 endif |
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114 endfor |
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115 endif |
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116 if (! isempty (v)) |
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117 v = v(find (keep)); |
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118 endif |
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119 endif |
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120 |
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121 ## Always return a column vector, because that's what the old one did |
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122 if (rows (v) > 1) |
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123 v = v.'; |
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124 endif |
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125 |
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126 endfunction |
