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1 function outstr = substr(str, offset, len, repl)
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2 %SUBSTR Extract a substring out of a string.
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3 %
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4 % SUBSTR(STRING, OFFSET, LENGTH) extracts a substring out of STRING with
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5 % given LENGTH starting at the given OFFSET. First character is at offset 0.
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6 % If OFFSET is negative, starts that far from the end of the string. If
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7 % LENGTH is omitted, returns everything to the end of the string. If LENGTH
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8 % is negative, removes that many characters from the end of the string.
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9 %
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10 % SUBSTR(STRING, OFFSET, LENGTH, REPLACEMENT) will not return the substring
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11 % as specified by STRING, OFFSET, and LENGTH (see above) but rather replace
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12 % it by REPLACEMENT and return the result.
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13 %
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14 % Examples:
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15 %
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16 % Get first character: substr(string, 0, 1)
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17 % Get last character: substr(string, -1, 1)
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18 % Remove first character: substr(string, 1)
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19 % Remove last character: substr(string, 0, -1)
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20 % Remove first and last character: substr(string, 1, -1)
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21 %
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22 % SUBSTR is a MATLAB version of the Perl operator with the same name.
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23 % However, unlike Perl's SUBSTR, no warning is produced if the substring is
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24 % totally outside the string.
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25
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26 % Author: Peter J. Acklam
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27 % Time-stamp: 2004-02-21 22:49:14 +0100
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28 % E-mail: pjacklam@online.no
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29 % URL: http://home.online.no/~pjacklam
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30
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31 % Check number of input arguments.
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32 error(nargchk(2, 4, nargin));
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33
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34 n = length(str);
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35
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36 % Get lower index.
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37 lb = offset + 1; % offset from beginning of string
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38 if offset < 0
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39 lb = lb + n; % offset from end of string
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40 end
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41 lb = max(lb, 1);
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42
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43 % Get upper index.
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44 if nargin == 2 % SUBSTR(STR, OFFSET)
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45 ub = n;
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46 elseif nargin > 2 % SUBSTR(STR, OFFSET, LEN)
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47 if len >= 0
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48 ub = lb + len - 1;
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49 else
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50 ub = n + len;
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51 end
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52 ub = min(ub, n);
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53 end
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54
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55 % Extract or replace substring.
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56 if nargin < 4
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57 outstr = str(lb : ub); % extract substring
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58 else
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59 outstr = [str(1:lb-1) repl str(ub+1:end)]; % replace substring
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60 end
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