Previous: If Special Operator, Up: Truth [Contents][Index]
The logical operators and and or resemble conditionals. Both take any
number of argument, but only evalue as many as they need to in order to decide
what to return. If all its arguments are ‘true’ (not ‘NIL’), then and
returns the value of the last one.
But if one of the arguments turns out to be fale, none of the arguments after
that get evaluated. Similarly for or which stops as soon as it finds an
argument that is true.
These two operators are macros. Like special operators, macros can cirumvent the usual evaluation rule.