Version: 4.2.1

3.11 Boxes

A box is like a single-element vector. It prints as #& followed by the printed form of the boxed value. A #& form can also be used as an expression, but since the resulting box is constant, it has practically no use.

Examples:

  > (define b (box "apple"))
  > b

  #&"apple"

  > (unbox b)

  "apple"

  > (set-box! b '(banana boat))
  > b

  #&(banana boat)

Boxes in Reference: PLT Scheme provides more on boxes and box procedures.