Ignore this. ;)
deftype and reify and all of that good stuff are now in the Clojure
master branch. Rich pulled new into master a few days ago.
On Jan 15, 4:09 am, Michael Wood <esiot...@gmail.com> wrote:
> 2010/1/15 Simon Brooke <still...@googlemail.com>:
>
>
>
> > OK, I'm trying to get seriously stuck in, and the first thing I'm
> > trying to do is reimplement an inference engine I first wrote in
> > Portable Standard Lisp and then in InterLisp-D in /idiomatic/ Clojure.
> > So please have patience with me...
>
> > If one has something which is strongly typed, is it idiomatic to make
> > a Java class to hold it?
>
> > I want a structure like this
>
> > (defstruct feature :name :default)
>
> > but I want in addition to constrain the binding of :name to be always
> > a Clojure keyword and the binding of :default to be always a boolean -
> > the Clojure values either true or false.
>
> > I've tried
>
> > (defstruct feature [#^Keyword :name] :default)
>
> #^something applies to the thing to the right of it. There's no need
> to enclose anything in square brackets. But this won't work here
> anyway:
>
> user=> (defstruct feature #^Keyword :name :default)
> java.lang.IllegalArgumentException: Metadata can only be applied to IMetas
> :default
> java.lang.Exception: Unmatched delimiter: )
>
> > but the reader spits an illegal argument exception. Is there different
> > syntax which the reader could parse? Or am I using the wrong kind of
> > thing?
>
> > Of course given that a struct is immutable I could have a make-feature
> > function which has type-hinted args:
>
> > (defn
> > #^{:doc "Make a feature safely"}
> > make-feature [#^Keyword name #^bool default]
> > (struct-map feature :name name :default default))
>
> defn also supports docstrings more directly like this:
>
> (defn make-feature
> "Make a feature safely"
> [...]
> (struct-map ...))
>
> > This works and does sort-of what I want - I can't guarantee that
>
> Does it?
>
> user=> (defn
> #^{:doc "Make a feature safely"}
> make-feature [#^Keyword name #^bool default]
> (struct-map feature :name name :default default))
> #'user/make-feature
> user=> (make-feature "some name" 42)
> {:name "some name", :default 42}
>
> > nothing outside my make-feature function will make features but I
> > don't think I need to. However, it feels clunky - I instinctively feel
> > there must be a better way. Is this what deftype should be used for?
> > If so, where is it documented? The book I'm using - Stuart Halloway's
> > 'Programming Clojure' - doesn't seem to have it (or if it has I've
> > missed it). Also, I don't seem to have deftype in my 1.1.0 rc3 build :
>
> > cc.journeyman.dtree.dtree=> (doc deftype)
> > java.lang.Exception: Unable to resolve var: deftype in this context
> > (NO_SOURCE_FILE:20)
>
> > I've also grepped the source code of clojure and failed to find it.
>
> It's not in any official release yet. In your git checkout do
> something like this to get it:
>
> $ git checkout -b new origin/new
>
> That will create a branch called "new" based on the "new" branch in
> Rich's repository. Then you can "git pull" as usual to keep it
> updated. If you want to switch back to master, just do "git checkout
> master".
>
> I've not tried deftype yet, so I don't know if it's what you're looking for.
>
> --
> Michael Wood <esiot...@gmail.com>
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
