A complete reference for Scheme's four quoting forms — how they work, when to use them, and the classic pitfall with (car '(list ...)) .

01 — The four quoting forms

Syntax Full form What it does
'x (quote x) Freezes x entirely — nothing inside is ever evaluated. Returns the raw data structure.
x ` (quasiquote x) Like quote, but allows selective evaluation inside via , and ,@.
,x (unquote x) Inside a quasiquote: forces evaluation of x and splices the result in.
,@x (unquote-splicing x) Inside a quasiquote: evaluates x (must be a list), then inlines all elements.

02 — How ' (quote) freezes a structure

; ' freezes everything inside — no evaluation happens at any depth
(define x 42)

'x            ; => x         the symbol x, not 42
'(+ 1 2)      ; => (+ 1 2)   a three-element list, not 3
'(1 2 3)      ; => (1 2 3)   a list of numbers — fine
'(list 1 2 3) ; => (list 1 2 3)  a four-element list; "list" is just a symbol

📌 Note

Inside a quoted expression, every identifier is a symbol, not a function reference. The names list, +, car — all become inert symbols when quoted.

03 — The classic pitfall — (car '(list 1 2 3))

; What does this return?
(car '(list 1 2 3))   ; => list   ← the SYMBOL "list", not 1 !

; Why? The quote freezes the whole expression.
; The list looks like this internally:
;   element 0: the symbol  list
;   element 1: the number  1
;   element 2: the number  2
;   element 3: the number  3
; car picks element 0, which is the symbol "list".

; (length '(list 1 2 3)) => 4, not 3 !

📌 Note

Many beginners write '(list 1 2 3) expecting it to behave like (list 1 2 3). It does not. ' prevents list from being called — it becomes a plain symbol sitting at the head of a 4-element list.

04 — The correct ways to build a list

; Goal: get (1 2 3) and apply car to get 1

; Option A — call the list function (no quote)
(car (list 1 2 3))       ; => 1  ✓

; Option B — quote a literal data list (no function name inside)
(car '(1 2 3))           ; => 1  ✓

; Wrong — don't mix quote with a function call inside
(car '(list 1 2 3))      ; => list  ✗

💡 Example

Use '(1 2 3) when the list contains only literal data (numbers, booleans, symbols you want verbatim). Use (list ...) when any element needs to be computed or when you're calling functions.

05 — Quasiquote — selective evaluation

(define x 42)
(define lst '(1 2 3))

`(a x b)      ; => (a x b)      no comma — x is still a symbol
`(a ,x b)     ; => (a 42 b)     ,x forces evaluation — 42
`(a ,@lst b)  ; => (a 1 2 3 b)  ,@lst splices the list in

; Mental model: backtick is a template, comma is ${...}
;   `(a ,x b)    →   `a ${x} b`      in JavaScript
;   `(a ,@lst b) →   `a ${...lst} b`

06 — Quasiquote in macros

This is the most common real-world use: building code templates in define-syntax or define-macro.