Unanswered Questions

11
votes
0answers
278 views

Why do Haskell functors only have derived types in their target category?

In Haskell, the Functor typeclass functor is defined as follows (see e.g. Haskell wiki): class Functor (f :: * -> *) where fmap :: (a -> b) -> f a -> f b As far as I understand (...
8
votes
1answer
240 views

Code Design: Delegation of arbitrary functions

On PPCG, we frequently have King of the Hill challenges, which pit different code bots against each other. We don't like limiting these challenges to a single language, so we do cross-platform ...
8
votes
1answer
181 views

Algorithm to generate Edges and Vertexes outwards from origin with max multiplicity of 3

I am creating a 2d game for a website where the universe can grow extremely large (basically infinitely large). Initially, the universe is composed of 6 stars that are an equal distance from the ...
7
votes
3answers
260 views

Best solution to authorize that a user is only allowed to modify/act with their own resources in a REST API

Background: Currently in the process of building out a REST API, using node w/express and it is consumed by a mobile app and eventually a (modern browser based) website. I'm trying to identify the ...
7
votes
0answers
253 views

How do I associate command objects with the right receiver?

I tried to use Command Pattern for implementing Undo and Redo in my project public abstract class Command { protected Form Receiver { set; get; } protected HtmlElement Element { set; get; } ...
7
votes
1answer
230 views

Heuristic Approach for Flexible DIFF Implementation

I have created a DIFF implementation to compare document revisions at work. It is based on An O(ND) Difference Algorithm and Its Variations. One thing that has become important is to take the list ...
6
votes
1answer
130 views

Explicit DAG instead of Vector Clocks for synchronisation

I've started looking at approaches to data synchronisation among a set of peers. The peers must be able to work in a disconnected way and then synchronise together to merge their local changes. Peers ...
6
votes
0answers
384 views

Object Constraint Language (OCL) for Stack in java.util package

I have an exam coming up and I'm looking at past papers to get some ideas of what to expect. I'm a bit stuck on the following one and would really appreciate if someone could give some example ...
5
votes
1answer
229 views

How to move from OOP object composition to FP function composition in C#

I have been working for a few weeks on a new web project and I am realizing that all I am doing is basically calculations and transformations on data, and that most of my classes do not contain any ...
5
votes
0answers
222 views

What lambda function optimizations, if any, are planned for Java 9 and beyond?

I'm working on a high-performance project where Java 8's lambda functions are enormously useful. I've found, however, that they're memory inefficient when used en masse. For example, suppose I need to ...
5
votes
0answers
72 views

How does the Free monad and Reactive Extensions correlate?

I come from a C# background, where LINQ evolved into Rx.NET, but always had some interest in FP. After some introduction to monads and some side-projects in F#, I was ready to try and step to the next ...
5
votes
0answers
107 views

Generating sort keys when reordering items

We have a number of items which the end user will be able to organize into a desired order. The set of items is unordered, but each item contains a sort key which can be modified. We're looking for ...
5
votes
3answers
81 views

How do I scale up a bot/service?

I have this bot that I've created for Twitter. It's written in Python. It lives on my Raspberry Pi and I've set up a cronjob to run it every 60 seconds. Part 2 of the project is to build a web app ...
5
votes
2answers
215 views

Why does ifstream.eof() not return TRUE after reading the last line of a file?

When a beginner starts off reading ifstreams, his/her instinct is to read the file using a loop that usually looks like this: while (!ifstream.eof() { ... } However, C++ programmers note that what ...
5
votes
1answer
152 views

Algorithm to generate all sets of m points in n x n x n cubic lattice which are unique under symmetry

I am implementing an algorithm which is going to be quite computationally complex, and want to try to make sure I'm not doing unnecessary work. There is an n x n x n cubic lattice, e.g. if n=2 this ...

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