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(Slot Options): Added example from Ludovic Courtès

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about difference between init-value, -form and -thunk.
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Neil Jerram 2006-09-27 17:49:38 +00:00
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5
doc/goops/ChangeLog
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@ -1,3 +1,8 @@
2006-09-27 Neil Jerram <neil@ossau.uklinux.net>
* goops.texi (Slot Options): Added example from Ludovic Courtès
about difference between init-value, -form and -thunk.
2006-04-21 Kevin Ryde <user42@zip.com.au>
* hierarchy.pdf: New file, converted from hierarchy.eps using

36
doc/goops/goops.texi
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@ -838,8 +838,40 @@ value (shared across all new instances of the class).
when a new instance is created and should return the desired initial
slot value. @var{init-form} is an unevaluated expression that gets
evaluated when a new instance is created and should return the desired
initial slot value. @var{init-keyword} is a keyword that can be used to
pass an initial slot value to @code{make} when creating a new instance.
initial slot value. @var{init-keyword} is a keyword that can be used
to pass an initial slot value to @code{make} when creating a new
instance.
Note that, since an @code{init-value} value is shared across all
instances of a class, you should only use it when the initial value is
an immutable value, like a constant. If you want to initialize a slot
with a fresh, independently mutable value, you should use
@code{init-thunk} or @code{init-form} instead. Consider the following
example.
@example
(define-class <chbouib> ()
(hashtab #:init-value (make-hash-table)))
@end example
@noindent
Here only one hash table is created and all instances of
@code{<chbouib>} have their @code{hashtab} slot refer to it. In order
to have each instance of @code{<chbouib>} refer to a new hash table, you
should instead write:
@example
(define-class <chbouib> ()
(hashtab #:init-thunk make-hash-table))
@end example
@noindent
or:
@example
(define-class <chbouib> ()
(hashtab #:init-form (make-hash-table)))
@end example
If more than one of these options is specified for the same slot, the
order of precedence, highest first is