Questions tagged [clojure]
Clojure is a general-purpose language supporting interactive development that encourages a functional programming style, and simplifies multithreaded programming.
91 questions
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How can we handle inserts/delete cases using Map like data structures in FP?
Let's say, that we keep track of students entering the auditorium using their IDs(Key) and their check-in time(Value) in a Map. We delete the entries once they move out of the auditorium. I want to ...
- 399
0
votes
1
answer
119
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In clojure, how to structure a simple reverse file search function to make it unit testable
I have the following pair of functions used for searching upwards for a configuration file:
(defn has-config? [path]
contains? (set (.list path)) "my-config")
(defn find-config-path [path]
(cond
...
- 119
-2
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1
answer
506
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Is Clojure a wrong choice for implementing Data Structures?
I am planning to improve my knowledge of Clojure and algorithms at the same time by implementing some known data structures in Clojure (e.g. linked lists, skip lists, bloom filter, etc.). However, I ...
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1
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0
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How Functional Programming addresses concurrent increment/decrement operations invoked by different users? [duplicate]
Using Functional language, How can 2 different parties achieve the result of increment/decrement operations concurrently?
For the below scenario, Let's say, I've 2 quantities in stock and 2 users in ...
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2
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How Functional Programming addresses concurrent increment/decrement operations invoked by different users?
Using Functional language, How can 2 different parties achieve the result of increment/decrement operations concurrently?
For the below scenario,
Let's say, I've 2 quantities in stock and 2 users in ...
- 399
37
votes
7
answers
9k
views
What are the functional equivalents of imperative break statements and other loop checks?
Let's say, I've the below logic. How to write that in Functional Programming?
public int doSomeCalc(int[] array)
{
int answer = 0;
if(array!=null)
{
for(...
- 399
2
votes
3
answers
969
views
Can functional programming used for solving problems which require randomness?
This older question tells us that in functional programming "true" randomness cannot be achieved since in FP functions are pure/idempotent and return the same value irrespective of number of ...
- 399
3
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2
answers
309
views
Should I provide partialed functions based on API call in Clojure?
I am designing a library to wrap an API with Clojure. The API requires user credentials to authenticate user related calls.
My first approach was to have functions that do each task the API can do:
(...
- 139
3
votes
1
answer
209
views
Efficient algorithm for deducing object type dynamically based on members
I am designing a DSL (in clojure, specifically; though this question is more general than that) in which 'entities' are tracked as immutable hashes/maps, and where the 'concept' membership of an ...
- 345
3
votes
0
answers
441
views
Clojure: Decomposing Logging, Metrics, and Business Logic from a Function
I was reading the post A Modern Architecture for FP that included a code snippet that the author wanted to decompose further. I don't know Haskell but I recognize enough to know that I've written many ...
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12
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1
answer
2k
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What practical problem results from lack of hygienic macros in Clojure?
I've heard that Clojure macros are easier to write but not as reliable as Racket's hygienic macros. My question has 2 parts:
How does gensym differ from hygienic macros?
What do Racket macros provide ...
- 284
14
votes
3
answers
6k
views
If you can use def to redefine variables how is that considered immutable?
Trying to learn Clojure and you can't help but be told continually how Clojure is all about immutable data. But you can easily redefine a variable by using def right? I get that Clojure developers ...
- 319
2
votes
0
answers
390
views
Implement FSM explicitly in re-frame/reagent/react?
I'm in the process of making a simple game using re-frame (and thus react and reagent), but I'm stuck at one point.
In
https://github.com/Day8/re-frame#control-via-fsm
they claim
Not every app ...
- 675
3
votes
1
answer
195
views
How can you write an activation function in a neural network to handle a layer architecture of arbitrary dimensions?
I am making a neural network in Clojure that can take an array of integers,and return a data structure representing the layers of a neural network: so (make-layers [1 4 5]) would evaluate to:
[[0] ...
- 290
1
vote
1
answer
222
views
Clojure NameSpace Design
I am new to Clojure and trying to get a handle on organizing a project's namespaces. I am working on a solver for the knapsack problem. Currently, I have broken the modules into files, but everything ...
- 525
1
vote
0
answers
120
views
Modular application - dependency as separate module?
I have a modular application written in Java based on NetBeans Modules (those details probably aren't so important :-) ) and I'd like to add another module written in Clojure language. Clojure ...
- 166
25
votes
7
answers
17k
views
"Use map instead of class to represent data" -Rich Hickey
In this video by Rich Hickey, the Clojure creator, he advises to use map to represent data instead of using a class to represent it, as done in Java. I don't understand how it can be better, since how ...
- 359
2
votes
0
answers
418
views
vert.x message bus architecture
A large part of the vert.x architecture is around the message bus, and message passing between verticals. The main idea I guess being that I can create multiple modules (possibly in multiple languages)...
- 1,341
1
vote
1
answer
826
views
What was the influence of Chris Okasaki's data structures on Scala? [closed]
I heard a friend say:
The first real use of Chris Okasaki's book was in Clojure's data structures
I heard another friend say:
No, they influenced the design of Scala in quite a subtle way.
My ...
- 4,849
11
votes
2
answers
4k
views
Approaching SICP in Clojure instead of Scheme
I am a third year bachelor student in a software engineering program, and I brought up the idea of reading SICP to an adviser to gain a deeper and more fundamental understanding of the principles ...
- 269
7
votes
2
answers
522
views
How to represent hard-to-calculate "properties" of "objects" in functional code?
I have a polyline "class" in my Clojure program, which is represented by a vector of points. (It's not really a class or anything.)
The polyline's length (in the geometric sense) is something that is ...
- 171
0
votes
1
answer
60
views
More idiomatic syntax for 2nd level vector value update
I'm pretty sure there has to be a more idiomatic way of writing this:
(defn update-2nd-level-vector
[map index value]
(assoc map :key1 (assoc (get map :key1) :key2 (-> map (get-in [:key1 :key2]...
- 175
2
votes
1
answer
610
views
Hot swap/plug components in clojure?
I'm using OSGi for some time and I really like the ability to swap/replace components while my application is running. I simply have to build my module and push it to the OSGi container.
Is there a ...
- 1,190
12
votes
1
answer
8k
views
Pattern matching in Clojure vs Scala
What are the key differences between pattern matching in these two languages? I am not referring to syntax, but capability, implementation details, range of use cases and necessity.
Scala ...
- 290
4
votes
2
answers
464
views
Evaluation order of expressions in Clojure?
I'm currently learning Clojure (my first functional programming language), and I'm curious as to its order of evaluation.
Here is an example:
(take 10 (cycle [1 2 3]))
If the cycle expression was ...
- 143
1
vote
1
answer
188
views
How to unit test hiccup template generating function?
How do I unit test a function that takes a list of maps and returns an HTML table with the same data in Clojure/Hiccup?
- 2,045
3
votes
3
answers
2k
views
Lisp/Clojure: Removing unnecessary parentheses through conventions
I am fascinated to Lisp as it is simple yet powerful. I am just a beginner and I know there have been lots of discussions on removing parentheses from Lisp and its dialects. Yet I request Lisp ninja's ...
- 143
3
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1
answer
280
views
What is the relation between clojure reducers and loop fusion
I just stumbled upon Clojure reducers library.
It looks a lot like loop fusion. However the term is not mentioned anywhere on the page. Is there a difference between the two?
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1
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Is it fair to say that "macros don't compose"?
On this blog post aphyr (who is a brilliant programmer) states:
Clojure macros come with some important restrictions. Because they’re expanded prior to evaluation, macros are invisible to functions. ...
- 4,849
3
votes
1
answer
625
views
Does Clojure borrow concurrency ideas from Haskell?
In code quarterly interview with Rich Hickey, Michael Fogus hints that Clojure borrows a lot from Haskell:
Fogus:
As someone who only knows Haskell enough to read the papers, Clojure appears to be ...
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4
votes
3
answers
332
views
Is there a reason for the crossover from the Ruby community to the Clojure Community?
When we look at the the overlap between the Ruby Community - we see the following overlaps:
Think Relevance (now Cognitect) has switched from Ruby to Clojure
Jay Fields has switched from Ruby to ...
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3
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1
answer
2k
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Why the Scala fascination with flatmap? (This doesn't seem to be the same for mapcat in the Clojure world) [closed]
In the Scala community - there is an apparent fascination with the FlatMap function.
Now I understand that FlatMap is significant because it is used for the bind part of a Monad. (and that the ...
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7
votes
1
answer
2k
views
How to refactor a Java singleton to Clojure?
I'm writing a simple game in Java and I want to learn Clojure, so I've decided to refactor my current Java code to Clojure. The problem is that I've coded so much in object-oriented languages that I ...
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11
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2
answers
955
views
Where do we put "asking the world" code when we separate computation from side effects?
According to Command-Query Separation principle, as well as Thinking in Data and DDD with Clojure presentations one should separate side effects (modifying the world) from computations and decisions, ...
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3
answers
1k
views
Why does Clojure neglect the uniform access principle?
My background is Ruby, C#, JavaScript and Java. And now I'm learning Clojure. What makes me feel uncomfortable about the later is that idiomatic Clojure seems to neglect the Uniform access principle (...
- 1,269
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votes
5
answers
5k
views
Python decorators and Lisp macros
When looking Python decorators someone made the statement, that they are as powerful as Lisp macros (particularly Clojure).
Looking at the examples given in PEP 318 it looks to me as if they are just ...
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46
votes
6
answers
10k
views
Why is "tight coupling between functions and data" bad?
I found this quote in "The Joy of Clojure" on p. 32, but someone said the same thing to me over dinner last week and I've heard it other places as well:
[A] downside to object-oriented programming ...
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0
votes
2
answers
274
views
What is the exact semantic of reduce in clojure?
The Clojure docs regarding (reduce f val coll) state:
If val is supplied, returns the result of applying f to val and the
first item in coll, then applying f to that result and the 2nd item,
etc....
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votes
1
answer
2k
views
Is Clojure development required to be open-source?
This question could be generalized to any language where the language development is open-source, potentially, but I'm most curious about Clojure specifically.
If Clojure (as a language) is open-...
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3
answers
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How do people get rid of conditional branches in Functional Programming?
Long running switch cases or if-else-if constructs are avoided in OOP using polymorphism wherever it is applicable.
instead of branching by matching a value, branching is done at class-level itself.
...
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3
answers
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When would I require a Macro instead of a function?
I am new to Clojure, I am new to Macros and I have no prior background in Lisp.
I went on to create my own switch case like form and ended up with this:
(defmacro switch-case [v cases default] (if (...
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47
votes
5
answers
10k
views
What did Rich Hickey mean when he said, "All that specificity [of interfaces/classes/types] kills your reuse!"
In Rich Hickey's thought-provoking goto conference keynote "The Value of Values" at 29 minutes he's talking about the overhead of a language like Java and makes a statement like, "All those interfaces ...
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0
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2
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527
views
Are there any Clojure libraries for p2p? [closed]
I'm a web developer, but lately I have been learning Clojure and now I'm interested in creating a p2p application. And since Clojure is a general purpose language, I guess I can just use that.
Any ...
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13
votes
2
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4k
views
Could we build a functional computer?
As mush as FP has done, in the end, all our programs are structured.
That is, it doesn't matter how pure or functional we make a them - they are always translated to assembly,
so what actually runs ...
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14
votes
1
answer
4k
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How to write readable Clojure Code?
I am new to Clojure. I can understand the code I write but it becomes too difficult to understand it later.It becomes difficult to match parentheses.
What are the generic conventions to follow ...
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votes
5
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4k
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Is Clojure's syntax really simpler than Scala's? [closed]
Argument which is always made in favour of Clojure is that.
The syntax is simpler and there is only one way of expressing code with no complicated rules.
However Scala has loads of different types ...
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votes
2
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2k
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Is Haskell/Clojure actually unsuited for dynamic systems such as particle simulation?
I've been told in previous questions that functional programming languages are unsuited for dynamic systems such as a physics engine, mainly because it's costly to mutate objects. How realistic is ...
- 5,860
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votes
2
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5k
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Are square brackets and curly braces in Clojure still S-expressions?
I am trying to learn Lisp and looking at all the Lisps out there and their differences.
I see that in some implementations of Scheme, you can use square brackets interchangeably with round brackets ...
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3
votes
2
answers
2k
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clojure/erlang/go for high volume server
I have a project that will need to handle 1000s of requests a second with a decent amount of processing for each. For the most part, the processing will be done on a list of items, basically ...
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27
votes
5
answers
12k
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In what programming language did "let" first appear?
I was wondering about the origins of the "let" used in Lisp, Clojure, and Haskell. Does anyone know which language it appeared in first?
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