8.16.0.4
1 About Descriptions
| (require scramble/about) | package: scramble-lib |
The about interface is useful for displaying a partial description of a value in a situation where simply printing or writing the value would be inappropriate. See also about<%>.
Returns a string describing v, if v implements the
prop:about interface; otherwise, if (has-about? v) is false,
then the string "(no description)" is returned.
Examples:
> (struct secret (bs) #:property prop:about (lambda (self) (format "~s-bit secret" (* 8 (bytes-length (secret-bs self)))))) > (define my-secret (secret #"hello")) > (error 'secure-op "secret is too short\n given: ~a" (about my-secret)) secure-op: secret is too short
given: 40-bit secret
> (about 'apple) "(no description)"
value
Property for structs to implement the about operation.
procedure
(has-about? v) → boolean?
v : any/c
Returns #t if v is an instance of a struct type that
implements the prop:about interface, #f otherwise.