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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} {} index (@var{s}, @var{t}) |
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22 ## Return the position of the first occurrence of the string @var{t} in the |
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23 ## string @var{s}, or 0 if no occurrence is found. For example, |
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24 ## |
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25 ## @example |
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26 ## index ("Teststring", "t") |
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27 ## @result{} 4 |
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28 ## @end example |
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29 ## |
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30 ## @strong{Caution:} This function does not work for arrays of strings. |
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31 ## @end deftypefn |
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32 |
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33 ## Author: Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> |
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34 ## Adapted-By: jwe |
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35 |
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36 function n = index (s, t) |
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37 |
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38 ## This is patterned after the AWK function of the same name. |
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39 |
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40 if (nargin != 2) |
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41 usage ("index (s, t)"); |
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42 endif |
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43 |
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44 if (!isstr (s) || !isstr (t) || all (size (s) > 1) || all (size (t) > 1) ) |
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45 error ("index: expecting string arguments"); |
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46 endif |
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47 |
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48 l_s = length (s); |
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49 l_t = length (t); |
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50 |
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51 if ( l_s == 0 || l_s < l_t ) |
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52 ## zero length source, or target longer than source |
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53 v = []; |
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54 |
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55 elseif ( l_t == 0 ) |
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56 ## zero length target: return first |
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57 v = 1; |
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58 |
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59 elseif ( l_t == 1 ) |
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60 ## length one target: simple find |
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61 v = find (s==t); |
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62 |
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63 elseif ( l_t == 2 ) |
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64 ## length two target: find first at i and second at i+1 |
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65 v = find (s (1 : l_s-1) == t (1) & s (2 : l_s) == t (2)); |
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66 |
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67 else |
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68 ## length three or more: match the first three by find then go through |
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69 ## the much smaller list to determine which of them are real matches |
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70 limit = l_s - l_t + 1; |
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71 v = find (s (1 : limit) == t(1) & s (2 : limit+1) == t (2) |
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72 & s (3 : limit+2) == t(3) ); |
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73 endif |
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74 |
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75 if (l_t > 3) |
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76 |
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77 ## force strings to be both row vectors or both column vectors |
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78 if (all (size (s) != size (t))) |
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79 t = t.'; |
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80 endif |
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81 |
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82 ## search index vector for a match |
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83 ind = 0 : l_t - 1; |
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84 n = 0; # return 0 if loop terminates without finding any match |
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85 for idx = 1:length(v) |
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86 if (s (v(idx) + ind) == t) |
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87 n = v(idx); |
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88 break; |
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89 endif |
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90 endfor |
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91 |
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92 elseif (length(v) > 0) |
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93 n = v(1); |
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94 |
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95 else |
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96 n = 0; |
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97 |
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98 endif |
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99 |
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100 endfunction |
