Atoms

Atoms are numbers or tokens. Atoms can be specified in single quotes. Single quotes are unneccessary if the atom contains only alphanumeric characters and does not start with an underscore or upper case character

The following are valid atoms

fred 'fred' : (quotes optional) 5 : (number) '5' : (token) 1.2 TODO!!! -4 'foo bar' ``foo bar'' 'X'