function alignment = pprintAlignment(as1, as2, left, right)

%PPRINTALIGNMENT   "Pretty-print" an alignment
%  Prints a sequence alignment, identifying places where
%  amino acid matches occur.

if (length(as1) ~= length(as2))
  error('Aligned sequences must have the same length');
end

% See if ranges where specified
if (nargin < 3) left  = 1;           end;
if (nargin < 4) right = length(as1); end;

% Definitions
chars_per_line = 60;
align_len  = right - left + 1;
num_lines  = floor(align_len+chars_per_line-1)/chars_per_line;
num_digits = floor(log10(right)+1);

% Identify places where sequences match
dots = blanks(length(as1));
for i=left:right
  if (as1(i) == as2(i))
    dots(i) = '.';
  end
end

% Pretty-print the alignment
alignment = [];
for i = 1:num_lines
  start_index = left + (i-1) * chars_per_line;
  end_index = min([start_index+chars_per_line-1, right]);

  l1 = sprintf('%0*d-%0*d: %s', num_digits, start_index, num_digits, ...
	       end_index, as1(start_index:end_index));
  l2 = sprintf('%0*d-%0*d: %s', num_digits, start_index, num_digits, ...
	       end_index, as2(start_index:end_index));
  l3 = sprintf('%0*d-%0*d: %s', num_digits, start_index, num_digits, ...
	       end_index, dots(start_index:end_index));

  alignment = strvcat(alignment, l1, l2, l3);
  if (i<num_lines) 
    alignment = strvcat(alignment, ' ');
  end
end

disp(alignment);