3.12 Boxes

Boxes in Guide: PLT Scheme introduces boxes.

A box is like a single-element vector, normally used as minimal mutable storage.

(box? v) → boolean?

v : any/c

Returns #t if v is a box, #f otherwise.

(box v) → box?

v : any/c

Returns a new mutable box that contains v.

(box-immutable v) → (and/c box? immutable?)

v : any/c

Returns a new immutable box that contains v.

(unbox box) → any/c

box : box?

Returns the content of box.

For any v, (unbox (box v)) returns v.

(set-box! box v) → void?

box : (and/c box? (not/c immutable?))

v : any/c

Sets the content of box to v.