Re: [ANN] com.dean.interval-tree

[Paulus Esterhazy]

Very cool, thanks for sharing!

This looks like it would be perfect for Advent of Code puzzles. Out of
curiosity, what are real-life problems that benefit from the use of an
interval map?

On Tue, Apr 6, 2021 at 2:04 PM danle...@gmail.com  wrote:
>
>
> https://github.com/dco-dev/interval-tree
>
> I’m pleased to announce that my company has released our first modest 
> contribution back to the Clojure community.
>
> In brief, this library provides “interval map”,  “interval set”, 
> “ordered-set”, and “ordered-map” collections, but more fundamentally we use 
> this as a library for building efficient, ordered collection types on an 
> extensible weight-balanced tree.
>
> This code has been in production for a few years now, however it is still 
> young in terms of a publicly released data-structure  library.   Comments and 
> suggestions are, of course, very much welcome!
>
> Best,
>
> Dan Lentz
> Dean & Company
>
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Re: Releasing scope-capture, a library for easing REPL-based debugging

[Paulus Esterhazy]

This looks great, thanks for publishing this, Val!

On Sun, Oct 8, 2017 at 9:09 AM, Val Waeselynck  wrote:
> Hi, I'm happy to release a tiny Clojure/Script library called scope-capture.
>
> https://github.com/alvalval/scope-capture
>
> Loosely speaking, scope-capture makes it trivial to reproduce from the REPL
> the context of a piece of code after it executed.
>
> It was inspired by Stuart Halloway's article REPL Debugging: no stacktrace
> required. Thanks Stu!
>
> I've been using it professionally for a few weeks now, and it's been a
> significant productivity boost for me. In my view the benefits are:
>
> easier debugging
> making Clojure code / projects more accessible to beginners
> easier ad-hoc exploration
>
> Please let me know what you think!
>
> Valentin Waeselynck
>
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Re: "GC overhead limit exceeded": Deceptive message?

[Paulus Esterhazy]

For background on "holding onto the head of a sequence" type problems, see

https://stuartsierra.com/2015/04/26/clojure-donts-concat

and

https://stackoverflow.com/questions/15994316/clojure-head-retention

On Tue, Aug 8, 2017 at 6:19 PM, Nathan Smutz  wrote:
> The one thing I'm aware of holding on to is a filtered file-seq:
> (def the-files (filter #(s/ends-with? (.getName %) ".xml" ) (rest (file-seq
> (io/file dw-path)
> There are 7,000+ files; but I'm assuming the elements there are just
> file-references and shouldn't take much space.
>
> The rest of the process is a transducer sequence:
> (def requirement-seq (sequence
>  (comp
>(map xml-zip-from-file)
>(remove degree-complete?)
>(map student-and-requirements))
>  the-files))
>
> Those functions are admittedly space inefficient (lots of work with
> zippers); but are pure.  What comes out the other end is a sequence of
> Clojure maps.  Could holding on to the file references prevent all that
> processing effluvia from being collected?
>
> The original files add up to 1.3 gigs altogether.  I'd expect the gleaned
> data to be significantly smaller; but I'd better check into how close that's
> getting to the default heap-size.
>
> Best,
> Nathan
>
> On Tuesday, August 8, 2017 at 1:20:21 AM UTC-7, Peter Hull wrote:
>>
>>
>> On Tuesday, 8 August 2017 06:20:56 UTC+1, Nathan Smutz wrote:
>>>
>>> Does this message sometimes present because the non-garbage data is
>>> getting too big?
>>
>> Yes, it's when most of your heap is non-garbage, so the GC has to keep
>> running but doesn't succeed in freeing much memory each time.
>> See
>> https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/memleaks002.html
>>
>> You can increases the heap but that might only defer the problem.
>>
>> As you process all your files, are you holding on to references to objects
>> that you don't need any more?
>
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Re: potential bug with pr-str+print

[Paulus Esterhazy]

Looks like a bug to me. ClojureScript doesn't seem to have this problem.

On Tue, May 2, 2017 at 7:50 AM, Jenny Finkel  wrote:
> Hello!
>
> I think I may have found a bug in clojure. When pr-str is called from within
> print, it doesn't produce a read-string-able string. Here is a simple
> example:
>
> user> (let [xs (doall (map #(pr-str %) ["a" "b"]))] (print xs))
> ("a" "b")
> user> (let [xs (map #(pr-str %) ["a" "b"])] (print xs))
> (a b)
>
> The reason is that print binds *print-readably* to nil, whereas pr-str does
> not bind it to true, even though I believe it should. If this really is a
> bug, I'd be happy to submit a patch for it.
>
> Thanks, Jenny
>
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Re: Diffing clojure data structures faster

[Paulus Esterhazy]

Great work, Dan! I think adding a way to diff standard clojure data
structures efficiently would open up very interesting possibilities.
Two examples:

- log changes in reagent's state-atom (clojurescript)
- build a simple durable "database" atom (persistent across process
restarts) using a diff-based write-ahead log (clojure)

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Re: Multiple key-value pairs in assoc-in (old issue)

[Paulus Esterhazy]

Just this week I have wished for an extended version of `assoc-in`
more than once. The reason is convenience, e.g. in the context of a
ring middleware:

(assoc-in response
   [:headers "Location"] "/homepage"
   [:session :user-id] user-id)

Extending `assoc-in` would also achieve parity with `assoc`, which
does accept multiple kv pairs.

On Wed, Aug 17, 2016 at 8:59 PM, Timothy Baldridge  wrote:
> When I see mailing list posts like this I like to play the devil's advocate
> a bit (at least in my own mind) and try to find problems with including a
> given patch in Clojure.
>
> A few things to consider:
> 1) There are really three answers to patches: "yes", "no" and "not now".
> That is to say, because a patch hasn't been accepted doesn't mean it's bad,
> it just means that it may not be the right time for the patch or perhaps
> there are other tickets more pressing for the version of Clojure under
> development. So don't let the time since patch creation disappoint you, it
> doesn't mean all hope is lost.
>
> 2) Now I ask myself: "Why would this be in core?" Looking at this function I
> see something interesting, there's nothing about this patch that couldn't be
> added as a utility function in some separate project. So why would I want to
> force the maintainers of Clojure, now and in the future, to support some
> extra logic? The best reason I can come up with is that it saves me
> copy-and-pasting some util function around, or perhaps it keeps me from
> including another util dependency in my projects. Is that convenience worth
> the cost? I don't know, and that's not my job, thankfully :) .
>
> 3) Now I ask my self: "When have I needed this feature?" And sadly, I can't
> think of a case. That's not to say I haven't needed to call assoc-in on many
> path/value pairs, but when I do I often use a construct like this:
>
> (reduce-kv assoc-in {}
>  {[:a :b] 42
>   [:c :d] 43
>   [:d] 11})
>
> In fact, I've been thinking about this for several days, and I have yet to
> think of a situation where I'd prefer 'apply' over reduce. And I can't think
> of a situation where I've need multiple hand-written arguments to assoc-in.
>
> I also think I haven't needed this functionality because I tend to prefer
> namespaced keywords and flat maps. Or when I do have nested maps, I use
> something like prewalk to do my work. This is anecdotal evidence, but it's
> my experience.
>
> None of these things are huge, but that's my thought process when reading
> about patches.
>
> Timothy
>
> On Mon, Aug 15, 2016 at 6:53 PM, Łukasz Kożuchowski
>  wrote:
>>
>> Thanks for the tip. I imagine the patch author is much more sad (it's been
>> one year...).
>>
>> Łukasz Kożuchowski
>>
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>
>
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Re: ClojureScript and React-native?

[Paulus Esterhazy]

Also give boot-react-native a try
(https://github.com/mjmeintjes/boot-react-native). It's a admittedly
bit rough to get started, but when set up offers a powerful
interactive working environment.

On Sun, May 29, 2016 at 4:12 PM, Mark Stang  wrote:
> Well, Re-natal seems to build and run.  I am still going through the
> exercises in the README.
>
> On Sat, May 28, 2016 at 7:16 PM, Mark Stang  wrote:
>>
>> Has anyone gotten it to work lately by building it from scratch?  And by
>> from scratch, I mean using the instructions on cljsrn.org?
>>
>> The natal how-to's end up with an error.
>>
>> And the Awesome project references a missing .h file, so it doesn't build.
>>
>> So, does anyone have a tutorial that works?
>>
>> thanks,
>>
>> Mark
>
>
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Re: Processing an array

[Paulus Esterhazy]

Here's how I would do it:

```
(defn to-timed-events [events]
  (->> events
   (reduce (fn [[acc-events acc-time] {:keys [duration], :as event}]
 [(conj acc-events (assoc event :time acc-time))
  (+ acc-time duration)])
   [[] 0])
   first))
```

A few comments:

1. Usually, if you're reaching for explicit recursion in Clojure,
consider using `reduce` instead. It's rare to find a problem that
can't be expressed more succinctly with `reduce`.

2. As another rule of thumb, if you're unsure how to model a sequence
transformation in Clojure, chances are that `reduce` is what you're
looking for. This is especially true if you're coming from an
imperative background, where people are not used to think in terms of
reduce/fold.

3. The step function needs to keep track of both the events seen so
far and the time of all previous events added together. This
"accumultator" value -- the first argument to the step function --
holds the intermediate result of the computation so far.

4. Because we need to keep track of two things (events and accumulated
time), the initial value passed to `reduce` is a pair (vector with two
elements). We use sequence destructuring to access both elements
easily in the step function.

5. We don't care about the accumulated time at the end. So we discard
it in the final step by extracting the events from the result using
`first`.

On Sun, Apr 24, 2016 at 12:01 PM, Olivier Scalbert  wrote:
> Hi all,
>
> I am a Clojure beginner 
> And I have an advice to ask !
>
> I have an array of events:
>
> (def events [
>   {:id "1" :duration 100}
>   {:id "2" :duration 200}
>   {:id "3" :duration 300}
> ])
>
> I wanted to transform this array into:
> [
>   {:id 1, :duration 100, :time 0} ; event 1 starts at 0
>   {:id 2, :duration 200, :time 100} ; event 2 starts when event 1 is
> finished, so at 100
>   {:id 3, :duration 300, :time 300} ; event 3 starts when event 2 is
> finished, so at 100 + 200
> ]
>
> Here is the function code:
>
> (defn to-timed-events
> ([time events] (to-timed-events time [] events))
> ([time timed-events events]
> (if (empty? events)
> timed-events
> (let [current (first events)
>   next-time (+ (:duration current) time)]
> (recur next-time (conj timed-events (assoc current :time time))
> (rest events))
> 
>
> It seems to work, but it looks a bit long for what it is doing. Is it
> possible to improve it ?
>
> Thanks for your help,
>
> Olivier
>
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