function run_demo(chunks, endings)%% Runs one of the demos defined in ../demo.%% Margins.marg.comments = '   ';marg.commands = '>> ';marg.question = '   ';marg.optional = '   Answer: ';% Predefined answers with special meanings.quit = {'quit', 'no'};start = {'start', 'again'};help = {'help'}special = {quit{:} start{:} help{:}};% Default questions and options.defq = 'Continue?';defo = {'yes', 'no'};endq = 'Quit or start again?';endo = {'quit', 'again'};% Predefined speil for help and which is always added to chunk(1).comments.speil = { ...  'Type answers to the questions to move through the demo.', ...  'Just hit the return key to get the default answer', ...  'which is always first in the list of suggestions.', ...  '', ...  'The following additional commands are also valid, even', ...  'though they may not be amongst the suggested answers:', ...  '  ''quit'' allows you to quit at any time,', ...  '  ''start'' returns you to the start of the demo,', ...  '  ''help'' prints out this help message.', ...  '', ...  'You only need to type enough letters to disambiguate', ...  'the answer. For example, ''q'' instead of ''quit'',', ...  'or ''y'' instead of ''yes''.', ...};% Init.answer = '';i = 1;fprintf('\n')% Loop through chunks.while i <= length(chunks)  % Clear the screen.  clc  fprintf('\n')  drawnow  % Get a chunk.  chunk = chunks(i);  % Print the comments.  comments = chunk.comments;  if ~isempty(comments)    if ischar(comments)      comments = substitute(comments, answer);      fprintf('%s%s\n', marg.comments, comments)    else      for j = 1:length(comments)        comment = substitute(comments{j}, answer);        fprintf('%s%s\n', marg.comments, comment)      end    end    fprintf('\n')  end  % If this is chunk(1) print the speil as well.  if i == 1    for j = 1:length(speil)      comment = speil{j};      fprintf('%s%s\n', marg.comments, comment)    end    fprintf('\n')  end  % Print (unless silent [starts with '%']) and run the commands.  commands = chunk.commands;  if ~isempty(commands)    nonshys = 0;    if ischar(commands)      commands = substitute(commands, answer);      if strncmp(commands,'%',1)        % Run silently.        eval(commands(2:end))      else        % Don't be shy.        fprintf('%s%s\n', marg.commands, commands)        eval(commands)        nonshys = nonshys + 1;      end    else      for j = 1:length(commands)        command = substitute(commands{j}, answer);        if strncmp(command,'%',1)          % Run silently.          eval(command(2:end))        else          % Don't be shy.          fprintf('%s%s\n', marg.commands, command)          eval(command)          nonshys = nonshys + 1;        end      end    end    if nonshys > 0      fprintf('\n')    end  end  % Supply a default question.  question = chunk.question;  optional = chunk.optional;  if isempty(question)    if i == length(chunks)      question = endq;      optional = endo;    else      question = defq;      optional = defo;    end  end  % Ask the question.  if ischar(question)    fprintf('%s%s\n', marg.question, question)  else    for j = 1:length(question)      query = question{j};      fprintf('%s%s\n', marg.question, query)    end  end  % Get the answer.  prompt = marg.optional;  for j = 1:length(optional)    option = optional{j};    if j == length(optional)      prompt = [prompt ' or '];    elseif j > 1      prompt = [prompt ', '];    end    prompt = [prompt option];  end  prompt = [prompt '? '];  possibles = uniquely_combine(optional, special);  while 1    fprintf('\n')    answer = lower(input(prompt, 's'));    if isempty(answer)      break;    end    k = find(strncmp(possibles, answer, length(answer)));    if length(k) == 1      answer = possibles{k};      if isempty(find(strcmp(answer, help)))        break;      else        % Print help message.        fprintf('\n')        for j = 1:length(speil)          fprintf('%s%s\n', marg.comments, speil{j})        end        fprintf('%s%s\n', marg.comments, '')        fprintf('%s%s\n', marg.comments, 'Continue?')      end    else      fprintf('\n')      if length(k) == 0        fprintf('%sUnrecognised: try:', marg.comments)        for j = 1:length(possibles)          if j > 1            if j == length(possibles)              fprintf(' or')            else              fprintf(',')            end          end          fprintf(' %s', possibles{j})        end        fprintf('\n')      else        fprintf('%sAmbiguous: could be:', marg.comments)        ambigles = possibles(k);        for j = 1:length(ambigles)          if j > 1            if j == length(ambigles)              fprintf(' or')            else              fprintf(',')            end          end          fprintf(' %s', ambigles{j})        end        fprintf('\n')      end    end  end  fprintf('\n')  % Default answer.  if isempty(answer)    answer = optional{1};  end  % Deal with the answer.  switch answer  case quit    break  case start    i = 1;    answer = '';  otherwise    i = i + 1;  endend% Clean up by executing the given command(s).clcif ~isempty(endings)  if ischar(endings)    eval(endings)  else    for j = 1:length(endings)      eval(endings{j})    end  endendfunction str = substitute(str, answer)% Substitue any occurrences of 'answer' in str with answer% but only if answer is not empty.if ~isempty(answer)  found = findstr('answer', str);  for i = length(found):-1:1    k = found(i);    str = [str(1:(k-1)) answer str((k+6):end)];  endendfunction c = uniquely_combine(c1, c2)% Combine cell arrays c1 and c2 into c but don't% repeat elements in c2 which are already in c1.c = c1;for i = 1:length(c2)  k = find(strcmp(c1, c2{i}));  if isempty(k)    c = {c{:} c2{i}};  endend