wolffd@0: function outstr = substr(str, offset, len, repl)
wolffd@0: %SUBSTR Extract a substring out of a string.
wolffd@0: %
wolffd@0: %   SUBSTR(STRING, OFFSET, LENGTH) extracts a substring out of STRING with
wolffd@0: %   given LENGTH starting at the given OFFSET.  First character is at offset 0.
wolffd@0: %   If OFFSET is negative, starts that far from the end of the string.  If
wolffd@0: %   LENGTH is omitted, returns everything to the end of the string.  If LENGTH
wolffd@0: %   is negative, removes that many characters from the end of the string.
wolffd@0: %
wolffd@0: %   SUBSTR(STRING, OFFSET, LENGTH, REPLACEMENT) will not return the substring
wolffd@0: %   as specified by STRING, OFFSET, and LENGTH (see above) but rather replace
wolffd@0: %   it by REPLACEMENT and return the result.
wolffd@0: %
wolffd@0: %   Examples:
wolffd@0: %
wolffd@0: %      Get first character:              substr(string,  0, 1)
wolffd@0: %      Get last character:               substr(string, -1, 1)
wolffd@0: %      Remove first character:           substr(string,  1)
wolffd@0: %      Remove last character:            substr(string,  0, -1)
wolffd@0: %      Remove first and last character:  substr(string,  1, -1)
wolffd@0: %
wolffd@0: %   SUBSTR is a MATLAB version of the Perl operator with the same name.
wolffd@0: %   However, unlike Perl's SUBSTR, no warning is produced if the substring is
wolffd@0: %   totally outside the string.
wolffd@0: 
wolffd@0: %   Author:      Peter J. Acklam
wolffd@0: %   Time-stamp:  2004-02-21 22:49:14 +0100
wolffd@0: %   E-mail:      pjacklam@online.no
wolffd@0: %   URL:         http://home.online.no/~pjacklam
wolffd@0: 
wolffd@0:    % Check number of input arguments.
wolffd@0:    error(nargchk(2, 4, nargin));
wolffd@0: 
wolffd@0:    n = length(str);
wolffd@0: 
wolffd@0:    % Get lower index.
wolffd@0:    lb = offset + 1;             % offset from beginning of string
wolffd@0:    if offset < 0
wolffd@0:       lb = lb + n;              % offset from end of string
wolffd@0:    end
wolffd@0:    lb = max(lb, 1);
wolffd@0: 
wolffd@0:    % Get upper index.
wolffd@0:    if nargin == 2               % SUBSTR(STR, OFFSET)
wolffd@0:       ub = n;
wolffd@0:    elseif nargin > 2            % SUBSTR(STR, OFFSET, LEN)
wolffd@0:       if len >= 0
wolffd@0:          ub = lb + len - 1;
wolffd@0:       else
wolffd@0:          ub = n + len;
wolffd@0:       end
wolffd@0:       ub = min(ub, n);
wolffd@0:    end
wolffd@0: 
wolffd@0:    % Extract or replace substring.
wolffd@0:    if nargin < 4
wolffd@0:       outstr = str(lb : ub);                        % extract substring
wolffd@0:    else
wolffd@0:       outstr = [str(1:lb-1) repl str(ub+1:end)];    % replace substring
wolffd@0:    end