define-struct creates a struct-like product type with named fields.

Syntax

(define-struct ⟨name⟩
  (⟨field-name⟩ ⟨docstring⟩? ⟨type⟩)...)

Semantics

  • Toplevel form to define a new struct-like data type.
  • Structs are useful when named fields are clearer than positional fields of define-type.
  • A field named f is accessed with the operator .f.
  • A struct name is conventionally written in CamelCase.

In release mode, the compiler can eliminate a locally constructed struct used only for field access. Field initializers still run once, in order. Passing, returning, or capturing the struct can prevent this optimization unless inlining exposes its field accesses.

Example

(define-struct Point
  (x Integer)
  (y Integer))

(let ((p (Point 1 2))
  (Point (.y p) (.x p))))