Editing Lisp (programming language) (section)

===Lists===
A Lisp list is written with its elements separated by [[Whitespace character|whitespace]], and surrounded by parentheses. For example, {{Lisp2|(1 2 foo)}} is a list whose elements are the three ''atoms'' {{Lisp2|1}}, {{Lisp2|2}}, and [[foo|{{#tag:syntaxhighlight|foo|lang=Lisp|inline=1}}]]. These values are implicitly typed: they are respectively two integers and a Lisp-specific data type called a "symbol", and do not have to be declared as such.

The empty list {{Lisp2|()}} is also represented as the special atom {{Lisp2|nil}}. This is the only entity in Lisp which is both an atom and a list.

Expressions are written as lists, using [[Polish notation|prefix notation]]. The first element in the list is the name of a function, the name of a macro, a lambda expression or the name of a "special operator" (see below). The remainder of the list are the arguments. For example, the function {{Lisp2|list}} returns its arguments as a list, so the expression
<syntaxhighlight lang="Lisp">
 (list 1 2 (quote foo))
</syntaxhighlight>
evaluates to the list {{Lisp2|(1 2 foo)}}. The "quote" before the {{Lisp2|foo}} in the preceding example is a "special operator" which returns its argument without evaluating it. Any unquoted expressions are recursively evaluated before the enclosing expression is evaluated. For example,
<syntaxhighlight lang="Lisp">
 (list 1 2 (list 3 4))
</syntaxhighlight>
evaluates to the list {{Lisp2|(1 2 (3 4))}}. The third argument is a list; lists can be nested.