Mauch MIREX 2010

%

%PARSECHORD parse chord symbol to its constituent string elements

% 

% [rootnote, shorthand, degreelist,

%              bass, success, errormessage] = parsechord(chord, {verbose})

% 	

% Parses the chord symbol string "chord" into its separate string elements. 

% 

% NOTE: This function does not check validity of the chord elements, it

% merely separates them according to the chord syntax. 

% To obtain chord elements with included validity check use GETCHORDINFO.

%

% Success = 1 if symbols parsed correctly, 0 otherwise.

%

% If optional argument 'verbose' is 1, function prints any errormessage to 

% the screen.

% 	

% returns:  rootnote        (note string)

%           shorthand       (shorthand string)

%           degreelist      (degree-list string)

%           bass            (degree string)

%           success         (boolean)

%           errormessage    (string)

%

% See also: getchordinfo                     

%

% Author: Christopher Harte,  August 2005

% 

% Copyright: Centre for Digital Music, Queen Mary University of London 2005 

%

% This file is part of the C4DM Chord Toolkit.  

%

% The C4DM Chord Toolkit is free software; you can redistribute it and/or 

% modify it under the terms of the GNU General Public License as published 

% by the Free Software Foundation; either version 2 of the License, or

% (at your option) any later version.

%

% The C4DM Chord Toolkit is distributed in the hope that it will be useful,

% but WITHOUT ANY WARRANTY; without even the implied warranty of

% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

% GNU General Public License for more details.

%

% You should have received a copy of the GNU General Public License

% along with the C4DM Toolkit; if not, write to the Free Software

% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

%		

function  [rootnote, shorthand, degrees, bass, success, errormessage] = parsechord(chord, verbose)

% set verbose default to 0

if nargin <2

    verbose = 0;

end

ilength = length(chord);

% initialise variables

errormessage = '';

rootnote = '';

shorthand = '';

degrees = '';

bass = '';

success = 1;

index = 1;

% check for 'no chord' symbol

if chord(index) == 'N'

    rootnote = chord(index);

    index = index +1;

    % check to see there are no further characters

    if(index<=ilength)

        errormessage = sprintf(['Error in parsechord: \nExtra characters after "no chord" symbol "' chord '"\n']); 

        success = 0;

    end

else

% parse thechord symbol

    % the first part of the symbol before a switch character should be the root note

    while ((index <=ilength ))

        if (chord(index) ==  ':') || (chord(index) ==  '/') || ...

           (chord(index) ==  '(') || (chord(index) ==  ')')

            break

        end

        rootnote(index) = chord(index);

        index = index+1;

        if(index > ilength) || (chord(index) == '/')

            % if chord is a rootnote on its own or with just a bass note 

            % then it is a major chord therefore set shorthand to 'maj'

            shorthand = 'maj';

        end

    end

    % initialise booleans to record which switch characters we have found

    colon = 0;

    openbracket = 0;

    closebracket = 0;

    slash = 0;

    % parse the rest of the chord symbol

    while(index <= ilength)

        % reset temporary index 

        tempindex = 1;

       switch(chord(index))

           case ':'  

               % if we find a colon after any switch characters have 

               % already occured then the symbol is incorrect 

               if (colon || openbracket || closebracket || slash)

                    errormessage = sprintf(['Error in parsechord: \nIncorrect character sequence in chord "' chord '"\n']); 

                    success = 0;

                    index = ilength+1;

               else

                   % found the first instance of a colon character

                   colon = 1;

                   index = index +1;

                   if(index > ilength)

                        errormessage = sprintf(['Error in parsechord: \nFound ":" at end of chord string "' chord '"\n']); 

                        success = 0; 

                   end

                   % colon should be followed by a shorthand string or

                   % a degree list contained in brackets

                   while (index <= ilength)

                       if (chord(index) ==  ':') || (chord(index) ==  '/') || ...

                          (chord(index) ==  '(') || (chord(index) ==  ')')

                           break

                       end

                       % copy character into shorthand

                       shorthand(tempindex) = chord(index);

                       index = index +1;

                       tempindex = tempindex +1;

                   end

               end

           case '('

               % if we have had a colon but no other switch charaters then

               % an open bracket signifies the start of the degree list

               if (colon && ~slash && ~closebracket && ~openbracket) 

                   openbracket = 1;

                   index = index +1;

                   while (index <= ilength)

                       if (chord(index) ==  ':') || (chord(index) ==  '/') || ...

                          (chord(index) ==  '(') || (chord(index) ==  ')')

                           break

                       end

                       % copy character into degrees

                       degrees(tempindex) = chord(index);

                       index = index +1;

                       tempindex = tempindex +1;

                   end

                   if(index > ilength)

                        errormessage = sprintf(['Error in parsechord: \nDegree list brackets not closed in chord "' chord '"\n']); 

                        success = 0; 

                   end

               else

                   errormessage = sprintf(['Error in parsechord: \nIncorrect character sequence in chord "' chord '"\n']); 

                   success = 0;

                   index = ilength +1;

               end

           case ')'

               % if we find a closing bracket then we should either be at

               % the end of the symbol or there should be a slash to follow

               if (colon && openbracket && ~slash && ~closebracket) 

                   closebracket = 1;

                   index = index +1;

               else

                   errormessage = sprintf(['Error in parsechord: \nIncorrect character sequence in chord "' chord '"\n']); 

                   success = 0;

                   index = ilength +1;

               end

               % check to see that the brackets contained something

               if isempty(degrees)

                   errormessage = sprintf(['Error in parsechord: \nBrackets contain no degrees in chord "' chord '"\n']); 

                   success = 0;

                   index = ilength +1;

               end

           case '/'

               % forward slash should be followed by a degree string

                   slash = 1;

                   % move on to next character to process the expected bass degree

                   index = index +1;

                   % check that we haven't overun the end of the symbol string

                   if(index > ilength)

                        errormessage = sprintf(['Error in parsechord: \nNo bass degree "/" at end of chord "' chord '"\n']); 

                        success = 0; 

                   end

                   % check that if we have had an open bracket that it also

                   % had a closed bracket

                   if(xor(openbracket,closebracket))

                        errormessage = sprintf(['Error in parsechord: \nFound "/" before closing bracket in chord "' chord '"\n']); 

                        success = 0; 

                        index = ilength +1;

                   end

                   % check that the previous character was not a ':'

                   if(chord(index-2) == ':')

                        errormessage = sprintf(['Error in parsechord: \nFound "/" directly after ":" in chord "' chord '"\n']); 

                        success = 0; 

                        index = ilength +1;

                   end

                   while( index <= ilength )

                       % if we find a switch character after a slash then

                       % the symbol is incorrect

                       if (chord(index) ==  ':') || (chord(index) ==  '/') || ...

                          (chord(index) ==  '(') || (chord(index) ==  ')')

                           errormessage = sprintf(['Error in parsechord: \nIncorrect character sequence in chord "' chord '"\n']); 

                           success = 0;

                           index = ilength +1;

                       else

                           % copy remaining characters into bass

                           bass(tempindex) = chord(index);

                           index = index +1;

                           tempindex = tempindex +1;

                       end

                   end

           otherwise

                errormessage = sprintf(['Error in parsechord: \nUnrecognised chord "' chord '"\n']); 

                success = 0;

                index = ilength + 1;

       end

    end

end            

if (verbose == 1) && (success == 0)

    fprintf(1,errormessage);

end