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margin-note to say #:auto-value is evaluated once

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ben 2016-02-24 17:18:45 -05:00
parent 81b5d74ed6
commit f2bef56a2e
1 changed files with 5 additions and 0 deletions
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pkgs/racket-doc/scribblings/reference/define-struct.scrbl
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@ -233,6 +233,11 @@ supplied, then the @racket[struct] form is equivalent to
(eval:error ellipse-width) (eval:error ellipse-width)
] ]
@margin-note{
Expressions supplied to @racket[#:auto-value] are evaluated once and shared
between every instance of the structure type. In particular, updates to
a mutable @racket[#:auto-value] affect all current and future instances.
}
If @racket[#:auto] is supplied as a @racket[field-option], then the If @racket[#:auto] is supplied as a @racket[field-option], then the
@tech{constructor} procedure for the structure type does not accept an @tech{constructor} procedure for the structure type does not accept an
argument corresponding to the field. Instead, the structure type's argument corresponding to the field. Instead, the structure type's