wolffd@0: function n = letter2num(l)
wolffd@0: 
wolffd@0: % map a-z to 1:26 and A-Z to 27:52
wolffd@0: punct_code = [32:47 58:64 91:96 123:126];
wolffd@0: digits_code = 48:57;
wolffd@0: upper_code = 65:90;
wolffd@0: lower_code = 97:122;
wolffd@0: 
wolffd@0: c = double(l);
wolffd@0: n = c-96;
wolffd@0: ndx = find(n <= 0); % upper case
wolffd@0: n(ndx) = c(ndx)  - 64 + 26;