if

• the "if", "then" and "else" parts are just lists in that order
• anything except nil and an empty list is 'truthy'

ways to test truth

numbers and markers

• =
• <
• >
• <=
• >=

strings

• equal - if objects are equal
• eq - if objects are the same object
• string<
• string-lessp
• string=
• string-equal