That works - thanks.
Still, it seems intuitive to build the code as I had originally done.
It's too bad code has to get complicated so quickly :)
Thank again for the help.
On Jan 3, 9:19 pm, Robert Marianski <r...@marianski.com> wrote:
> On Tue, Jan 03, 2012 at 07:22:22PM -0800, Trevor wrote:
> > hmmm.... macro question:
>
> > ; here's a macro that assembles many puts. It serves no purpose to me
> > (and doesn't even make sense in its current form). It's just something
> > I hit playing around and learning macros.
>
> > (defmacro doto-putter [x y xs]
> > `(doto (java.util.HashMap.)
> > (.put ~x ~y)
> > ~@(for [[k v] xs]`(.put ~k ~v))))
>
> > user=> (doto-putter "c" 3 {"a" 1 "b" 2})
> > #<HashMap {b=2, c=3, a=1}>
>
> > however:
>
> > =>(defn omg [x y xs](doto-putter x y xs))
> > CompilerException java.lang.IllegalArgumentException: Don't know how
> > to create ISeq from: clojure.lang.Symbol, compiling:(NO_SOURCE_PATH:2)
>
> > I'm thinking the issue seems to be that it's not resolving xs because
> > this works:
>
> > (defmacro doto-putter [x y]
> > `(doto (java.util.HashMap.)
> > (.put ~x ~y)
> > ~@(for [[k v]{"a" 1 "b" 2}]`(.put ~k ~v))))
>
> > user=> (defn omg [x y](doto-putter x y))
> > #'user/omg
>
> > user=>(omg "c" 3)
> > #<HashMap {b=2, c=3, a=1}>
>
> > what am I missing? None of my other macros have this problem.
>
> Keep in mind that you are trying to iterate through xs at compile time.
> All you have at that point is a symbol, so effectively you are trying
> this:
> (for [[k v] 'xs] ...)
>
> That's why you are getting the error above; you are trying to iterate
> through a symbol. There isn't a way around this, because it's impossible
> to know the keys/values at compile time.
>
> What you need to do instead is generate the code to iterate through the
> map instead of actually iterating through at compile time. Something
> like this:
>
> (defmacro doto-putter [x y xs]
> `(let [h# (java.util.HashMap.)]
> (.put h# ~x ~y)
> (dorun (for [[k# v#] ~xs]
> (.put h# k# v#)))
> h#))
>
> Hope that helps,
> Robert
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