Constants

A Constant is one of:

• Atom
• Integer
• Real Number

Atoms are made up of:

• letters and digits: AB...Zab...z01...9 and _ (underscore)
• symbol: any number of +, -, *, /, , SPM_quot^", <, >, =, ~, :, ., ?, @, #, $ &
• quoted strings: 'any old character' ---but the single quote character is handled specially

Normally, atoms start with a lower case letter. Note that, in a quoted atom, you can include a `` ' '' by prefixing it with another `` ' ''. So, to print a `` ' '' on the screen you will need a goal like write(' ' ' ').