4.1.2 Literal expressions

Syntax:  (quote <datum>)
Syntax:  '<datum>
Syntax:  <constant>

(quote <datum>) evaluates to <datum>. <Datum> may be any external representation of a Scheme object (see section 3.3). This notation is used to include literal constants in Scheme code.

  (quote a)                     =>  a
  (quote #(a b c))              =>  #(a b c)
  (quote (+ 1 2))               =>  (+ 1 2)

(quote <datum>) may be abbreviated as '<datum>. The two notations are equivalent in all respects.

  'a                   =>  a
  '#(a b c)            =>  #(a b c)
  '()                  =>  ()
  '(+ 1 2)             =>  (+ 1 2)
  '(quote a)           =>  (quote a)
  "a                  =>  (quote a)

Numerical constants, string constants, character constants, and boolean constants evaluate "to themselves"; they need not be quoted.

  '"abc"     =>  "abc"
  "abc"      =>  "abc"
  '145932    =>  145932
  145932     =>  145932
  '#t        =>  #t
  #t         =>  #t

As noted in section 3.4, it is an error to alter a constant (i.e. the value of a literal expression) using a mutation procedure like set-car! or string-set!.