The filter documentation reads:
Returns a lazy sequence of the items in coll for which (pred item)
returns true. pred must be free of side-effects.
So that means I should not write a function like this:
(defn unique [sc]
Returns a lazy sequence with all consecutive duplicates removed
(let
, Rowdy Rednose rowdy.redn...@gmx.net wrote:
The filter documentation reads:
Returns a lazy sequence of the items in coll for which (pred item)
returns true. pred must be free of side-effects.
So that means I should not write a function like this:
(defn unique [sc]
Returns a lazy sequence
is a better demo of how do I maintain state
across a lazy sequence without requiring any mutation?
Stu
Hi,
On Feb 18, 3:04 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Returns a lazy sequence of the items in coll for which (pred item)
returns true. pred must be free of side-effects
am, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Various interesting approaches to this problem... thanks guys!
Stu, you're right, distinct builds up a set of all items encountered,
which I don't need, and it's costly. But that function it is indeed a
good model. So here's a side effects
:
On Sat, Jan 30, 2010 at 7:31 PM, Rowdy Rednose rowdy.redn...@gmx.net wrote:
I want to have it in O(1). That's why I use a tree map in the first
place.
On Jan 31, 9:15 am, Sean Devlin francoisdev...@gmail.com wrote:
If you can live with an O(n) operation, take/drop-with will do the
job
How would I do something like these 3 TreeMap operations with
clojure's sorted-map?
The goal is to narrow down a map to include only keys with a given
prefix.
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I want to have it in O(1). That's why I use a tree map in the first
place.
On Jan 31, 9:15 am, Sean Devlin francoisdev...@gmail.com wrote:
If you can live with an O(n) operation, take/drop-with will do the
job.
Sean
On Jan 30, 6:59 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
How would
Does anybody know an elegant way to have a regex pattern with
capturing groups like in this simple example:
user= (def pat #^foo=([^;]*);bar=([^;]*);$)
#'user/pat
user= (re-seq pat foo=F0o;bar=bAr;)
([foo=F0o;bar=bAr; F0o bAr])
And reuse that pattern to generate a text that replaces the groups
Thanks Meikel,
your negative answer actually helped me analyze my problem better and
get the distinction run time / expansion time straight. I figured that
the names of the bindings are already there at expansion time and it's
only the values that I need to retrieve at run time.
So this version
As I said, the example was stripped down for simplicity, and that
simple version doesn't make much sense other than for communicating my
problem.
My real val-fn is not a map, it's indeed a couple of functions,
applied to some data that's passed in. But the result of that acts
like a map: it
Hi all,
in my quest to learn clojure (and lisp in general), I'm currently
trying to translate some the On Lisp code to clojure.
The first couple of functions and macros in Chapter 19 A Query
Compiler read:
(defun make-db (optional (size 100))
(make-hash-table :size size))
(defvar
On Jul 19, 12:53 pm, Richard Newman holyg...@gmail.com wrote:
* Can the body of the db-push function be simplified?
I think so. Untested:
(defn db-push
([key val] (db-push key val *default-db*))
([key val db]
(swap! db assoc key (cons val (db key))
If I add an @ it runs:
How can I lexically bind names like let does in a macro, when names
and values for those bindings are passed in?
This here works fine when I pass a literal collection:
(defmacro let-coll
[coll body]
`(let ~(vec coll) ~...@body))
user= (let-coll [a 11 b 22] (list b a))
(22 11)
Doing the
Why does the Snake example in the book use refs when all mutation is
done from the EDT?
To verify that, I put a call to assert-edt in front of every dosync
in snake.clj. assert-edt is defined like this:
(defn assert-edt [] (assert (javax.swing.SwingUtilities/
isEventDispatchThread)))
And it
On Jul 10, 10:28 pm, Stuart Halloway stuart.hallo...@gmail.com
wrote:
binding to a thread. The snake game could be extended to be a
simulation that runs on multiple threads (or perhaps even multiple
Makes sense. For the example in the book it just seemed completely
redundant. And when
This did the trick:
(ns clojure.core)
(defmacro dosync [ body]
`(do
(assert (not (javax.swing.SwingUtilities/isEventDispatchThread)))
(#'dosync ~...@body)))
This is great for testing!
Thanks for your help, Stu. And btw the book is really great so far
(and I'm almost through)! It
refer to the original dosync from my new dosync
macro?
On Jul 10, 11:52 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
This did the trick:
(ns clojure.core)
(defmacro dosync [ body]
`(do
(assert (not (javax.swing.SwingUtilities/isEventDispatchThread)))
(#'dosync ~...@body
The idea is to have all existing code (that gets recompiled after my
redefinition) benefit from my changes automatically, although I fear
it's not considered good style to do this.
--~--~-~--~~~---~--~~
You received this message because you are subscribed to the
schrieb Rowdy Rednose:
user= (dosync (alter gnu-rms update-in [:key1 :key2 :key3] #(conj %
foo)))
{:key1 {:key2 {:key3 #{foo
You actually don't need the anonymous function...
(dosync
(alter gnu-rms update-in [:key1 :key2 :key3] conj foo))
Sincerely
Meikel
smime.p7s
Say I have a data structure like this
(def ref-map-map-map-set (ref {:key1 {:key2 {:key3 #{))
If I want to add a new member to the set which is the value of :key3,
I currently do this:
(dosync
(let [key1 (:key1 @ref-map-map-map-set)
key2 (:key2 key1)
key3 (:key3 key2)]
:07 AM, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Say I have a data structure like this
(def ref-map-map-map-set (ref {:key1 {:key2 {:key3 #{))
If I want to add a new member to the set which is the value of :key3,
I currently do this:
(dosync
(let [key1 (:key1 @ref-map-map-map
On Jul 5, 1:23 pm, Richard Newman holyg...@gmail.com wrote:
However, I'd point out that:
* This might be a sign that you're doing things 'wrong'.
Could be. I'm still figuring out how to do things the functional way.
The reason I have these nested maps is to give my data structure. I
don't
On Jul 5, 1:20 pm, Adrian Cuthbertson adrian.cuthbert...@gmail.com
wrote:
(dosync (alter rms assoc-in [:key1 :key2 :key3] foo))
{:key1 {:key2 {:key3 foo}}}
I just found update-in, which is even better, as I want to update a
set:
user= (def gnu-rms (ref {:key1 {:key2 {:key3 #{))
On Jul 1, 12:02 am, Chouser chou...@gmail.com wrote:
You could wrap a Ref around every value, if you chose, to
allow independent changes to different rows at the same
time -- though this would not help when inserting rows.
I guess having millions of Refs would not perform too well. Plus you
that... :)
On Jul 1, 9:18 pm, Matt Culbreth mattculbr...@gmail.com wrote:
On Jul 1, 8:02 am, Rowdy Rednose rowdy.redn...@gmx.net wrote:
But it looks like I have to implement that myself - which is not a
complaint, but I'm trying to estimate the amount of work necessary.
But I guess I could just
Would it be easy to implement an in-memory database in clojure that
allows concurrent access?
It sounds pretty easy, as most of the features are already provided by
Clojure. I'm not sure though about the locking granularity.
Of course you don't pessimistically lock in Clojure, but if you have a
I find the pdf actually pretty useful as a quick reference until I'm
familiar with all the function names.
There's however a small mistake on page 28. The 'd' doesn't belong
there in the 2nd line of this example:
(let [{a :a, b :b, c :c, :as m :or {a 2 b 3}} {:a 5 :c 6}]
[a b c d m])
- [5 3 6
Was it a deliberate decision to make io! optional or is this by
accident? I know it came in later
I guess it's hard to do considering all access to Java would have to
be categorized, which is impossible, I guess.
It just seems like Clojure loses a lot by not guaranteeing side-effect-
freeness,
18, 3:21 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Say I've got this map of keys to integer values:
(def m {:one 0 :two 0 :three 0})
I want to write a function inc-values-in-map that takes such a map,
a collection of keys and will increment those keys' values in the map.
In other
] (assoc m k (f (m k default map keys)))
On Jun 18, 5:06 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Thanks for the ideas guys
I especially like the reduce/assoc approach. It's the one most clear
to me so far and also the most efficient one, I guess, as it does only
one assoc per changed key
Interesting. It's a bit different from what I currently need, but I'm
currently looking at the sources. I wondered why you define this:
(defn list-to-map
[ params]
(apply hash-map
(reduce concat (partition 2 params
Couldn't you just use the plain hash-map function?
user= (=
Say I've got this map of keys to integer values:
(def m {:one 0 :two 0 :three 0})
I want to write a function inc-values-in-map that takes such a map,
a collection of keys and will increment those keys' values in the map.
In other words, calling
(inc-values-in-map m [:one :three])
should
Thanks guys, these solutions look much better already.
But do I always have to have these 2 steps
* merge collection
* split collection
It feels a bit inefficient, I don't know if it actually is, though.
On Mar 24, 8:05 pm, Phlex ph...@telenet.be wrote:
On 24/03/2009 1:06, pmf wrote:
On
Thanks all,
microbenchmarking shows that a simple
(time (doseq [[a b] (map vector list-a list-b)]))
is ~50% faster on my system than
(def par-doseq-fn (comp dorun map))
(defmacro par-doseq [bindings body]
(let [bindings (partition 2 bindings)]
`(par-doseq-fn (fn ~(vec (map first
Hi group,
say I have 2 sequences
(def seq-a '(a1 a2 a3))
(def seq-b '(b1 b2 b3))
and want to iterate over them in parallel, like this
(par-doseq [a seq-a b seq-b] (prn a b))
which should print
a1 b1
a2 b2
a3 b3
The way I do it currently is using map (and last to fight
lazyness):
(last
All the clojure swing examples I've seen so far use JTables in a
static way, i.e. the data is not programmatically modified once the
table got created.
Has anyone actually tried to implement a TableModel that is backed by
a clojure Vector/Map and fires events to TableModelListeners when the
. You could then do something like
(map = old_vec new_vec)
And then look for false results in the array and send a notification to
Swing.
On Fri, Feb 20, 2009 at 5:40 AM, Rowdy Rednose rowdy.redn...@gmx.netwrote:
All the clojure swing examples I've seen so far use JTables in a
static way
What is the easiest way to make clojure's get function evaluate the
value for 'not-found' only if the key is not found? Do I have to write
a macro like
(defmacro my-get [map key not-found]
`(if (contains? ~map ~key)
(get ~map ~key)
~not-found))
as long as it is not realized yet...
Still, this definitely is a doable workaround. Thanks!
-Luke
On Dec 29, 9:17 pm, Rowdy Rednose rowdy.redn...@gmx.net wrote:
What if you run the Swing code in the Event Dispatch Thread?
In other words, does this:
(. javax.swing.SwingUtilities
wrote:
Wow... that actually fixes it. Still a minor problem, since according
to the Sun website, it is legal to create a Swing object in another
thread as long as long as it is not realized yet...
Still, this definitely is a doable workaround. Thanks!
-Luke
On Dec 29, 9:17 pm, Rowdy Rednose
What if you run the Swing code in the Event Dispatch Thread?
In other words, does this:
(. javax.swing.SwingUtilities (invokeAndWait #(.
javax.swing.JOptionPane (showMessageDialog nil Hello World
or
(. javax.swing.SwingUtilities (invokeLater #(. javax.swing.JOptionPane
(showMessageDialog
land in an easy manner?
On 16 Dez., 20:58, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Can I listen on changes done to refs?
Let's say in a scenario like that
onhttp://en.wikibooks.org/wiki/Clojure_Programming#Mutation_Facilities
could I add a facility that allows the registration of listeners
it will probably not be in 1.0
On 20 Dez., 11:30, Chouser chou...@gmail.com wrote:
On Fri, Dec 19, 2008 at 8:35 PM, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Apart from being blasphemous - would it be a good idea to override
clojure.lang.Ref in Java land?
I want to create (children of?) refs
The structure of the wikibook page has changed and that link doesn't
work any more.
This will:
http://en.wikibooks.org/wiki/Clojure_Programming/Concepts#Mutation_Facilities
On 16 Dez., 20:58, Rowdy Rednose rowdy.redn...@gmx.net wrote:
Can I listen on changes done to refs?
Let's say
If Rich adds watchers for refs, would watchers be notified inside the
transaction?
I'm actually trying to get a notification after a transaction
successfully finished. Although there might be use cases for firing
events inside the transaction.
On 17 Dez., 00:37, Stuart Sierra
There must be a smarter way to achieve this than polling the
collection for changes, I guess.
On 16 Dez., 21:43, Dave Griffith dave.l.griff...@gmail.com wrote:
Right now, you add listeners to agents, but not refs. IIRC, there
was talk of adding listeners to refs to enable just the sort of
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