3.11 Boxes
A box is like a single-element vector. It can print as a quoted #& 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: Racket provides more on boxes and box procedures.