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1 ## Copyright (C) 1996, 2006 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 ## @deftypefnx {Function File} {} index (@var{s}, @var{t}, @var{direction}) |
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23 ## Return the position of the first occurrence of the string @var{t} in the |
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24 ## string @var{s}, or 0 if no occurrence is found. For example, |
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25 ## |
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26 ## @example |
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27 ## index ("Teststring", "t") |
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28 ## @result{} 4 |
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29 ## @end example |
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30 ## |
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31 ## If @var{direction} is @samp{"first"}, return the first element found. |
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32 ## If @var{direction} is @samp{"last"}, return the last element found. |
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33 ## The @code{rindex} function is equivalent to @code{index} with |
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34 ## @var{direction} set to @samp{"last"}. |
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35 ## |
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36 ## @strong{Caution:} This function does not work for arrays of |
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37 ## character strings. |
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38 ## @seealso{find, rindex} |
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39 ## @end deftypefn |
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40 |
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41 ## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> |
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42 ## Adapted-By: jwe |
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43 |
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44 function n = index (s, t, direction) |
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45 |
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46 ## This is patterned after the AWK function of the same name. |
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47 |
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48 if (nargin < 2 || nargin > 3) |
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49 print_usage (); |
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50 elseif (nargin < 3) |
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51 direction = "first"; |
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52 endif |
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53 direction = lower (direction); |
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54 |
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55 if (! (ischar (s) && ischar (t) && isvector (s) && isvector (t))) |
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56 error ("index: expecting character string arguments"); |
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57 elseif (! strcmp (direction, {"first", "last"})) |
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58 error ("index: direction must be either \"first\" or \"last\""); |
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59 endif |
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60 |
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61 l_s = length (s); |
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62 l_t = length (t); |
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63 |
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64 n = 0; |
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65 if (l_s == 0 || l_s < l_t) |
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66 ## zero length source, or target longer than source |
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67 ## return 0 |
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68 v = []; |
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69 |
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70 elseif (l_t == 0) |
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71 ## zero length target: return first |
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72 v = 1; |
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73 |
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74 elseif (l_t == 1) |
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75 ## length one target: simple find |
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76 v = find (s==t, 1, direction); |
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77 |
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78 elseif (l_t == 2) |
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79 ## length two target: find first at i and second at i+1 |
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80 v = find (s (1:l_s-1) == t(1) & s(2:l_s) == t(2), 1, direction); |
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81 |
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82 else |
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83 ## length three or more: match the first three by find then go through |
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84 ## the much smaller list to determine which of them are real matches |
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85 limit = l_s - l_t + 1; |
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86 v = find (s (1:limit) == t(1) |
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87 & s (2:limit+1) == t(2) |
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88 & s (3:limit+2) == t(3)); |
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89 if (strcmp (direction, "last")) |
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90 v = v(length(v):-1:1); |
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91 endif |
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92 |
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93 if (l_t > 3) |
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94 |
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95 ## force strings to be both row vectors or both column vectors |
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96 if (all (size (s) != size (t))) |
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97 t = t.'; |
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98 endif |
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99 |
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100 ## search index vector for a match |
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101 ind = 0:l_t-1; |
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102 ## return 0 if loop terminates without finding any match |
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103 for idx = 1:length(v) |
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104 if (s (v(idx) + ind) == t) |
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105 n = v(idx); |
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106 break; |
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107 endif |
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108 endfor |
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109 endif |
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110 |
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111 endif |
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112 |
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113 if (n == 0 && ! isempty (v)) |
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114 ## return the first found if n is not already set and v is not empty |
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115 n = v(1); |
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116 endif |
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117 |
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118 endfunction |
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119 |
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120 ## Test the function out |
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121 %!assert(index("astringbstringcstring", "s"), 2) |
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122 %!assert(index("astringbstringcstring", "st"), 2) |
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123 %!assert(index("astringbstringcstring", "str"), 2) |
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124 %!assert(index("astringbstringcstring", "string"), 2) |
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125 |
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126 ## test everything out in reverse |
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127 %!assert(index("astringbstringcstring", "s", "last"), 16) |
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128 %!assert(index("astringbstringcstring", "st", "last"), 16) |
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129 %!assert(index("astringbstringcstring", "str", "last"), 16) |
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130 %!assert(index("astringbstringcstring", "string", "last"), 16) |
