You're correct. They both do the same thing. Both do not update mtr-
map. Clearly I need to assign a local variable in a let statement.
(mtr-map passed as parameter version)
(def mtr-seq ["a" 1 "b" 2 "c" 3 "d" 4])
(defn map-mtr
[read-map premid reading]
(conj read-map {premid reading}))
(map-mtr mtr-map (first mtr-seq) (first (rest mtr-seq)))
{"a" 1}
mtr-map
{}
(version with def mtr-map)
(defn map-mtr
[premid reading]
(conj mtr-map {premid reading}))
#'user/map-mtr
user=> (map-mtr (first mtr-seq) (first (rest mtr-seq)))
{"a" 1}
user=> mtr-map
{}
On Jun 30, 12:05 pm, Mark Rathwell <[email protected]> wrote:
> It shouldn't. I can't duplicate what I think you are saying. Would you be
> able to you print the code you entered in the repl that produced these
> results?
>
> On Thu, Jun 30, 2011 at 12:02 PM, octopusgrabbus
> <[email protected]>wrote:
>
>
>
>
>
>
>
> > Thanks you for answering.
>
> > I should rephrase the question, and I'll go look at the links you
> > posted.
>
> > I'm wondering why conj worked in the first of the function that
> > operated on the mtr-map defined by def, and not in the version where
> > mtr-map was passed in as the first parameter.
>
> > On Jun 30, 11:48 am, Mark Rathwell <[email protected]> wrote:
> > > Clojure data structures are immutable by default (seehttp://
> > clojure.org/functional_programming).
>
> > > For mutability, see the following:
>
> > >http://clojure.org/vars
> > > <http://clojure.org/vars>http://clojure.org/atoms
>
> > >http://clojure.org/refs
>
> > >http://clojure.org/agents
>
> > >http://clojure.org/transients
>
> > > On Thu, Jun 30, 2011 at 11:35 AM, octopusgrabbus
> > > <[email protected]>wrote:
>
> > > > Given this empty map,
>
> > > > (def mtr-map {})
>
> > > > this sequence,
>
> > > > (def mtr-seq ["a" 1 "b" 2 "c" 3 "d" 4])
>
> > > > this function,
>
> > > > (defn map-mtr
> > > > [read-map premid reading]
> > > > (conj read-map {premid reading}))
>
> > > > and this call
>
> > > > (map-mtr mtr-map (first mtr-seq) (first (rest mtr-seq)))
>
> > > > mtr-map won't update, but redefining the function to take premid and
> > > > reading and allowing the function to operate on the global variable
> > > > mtr-map.
>
> > > > (defn map-mtr
> > > > [premid reading]
> > > > (conj mtr-map {premid reading}))
>
> > > > mtr-map becomes updated.
>
> > > > I'm confused as to how to update mtr-map by allowing it to be passed
> > > > into the function in the first example.
>
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