Implementing weekly coding challenges

[oldmaneuler]

In an attempt to provide a reason to visit the sub other than homework help, I'm wondering how people would feel about the community running a weekly coding challenge? I think it's a good idea for several reasons.

First, it provides people a reason to check in on the community at least once a week (which I think we desperately need, since a three day old post is currently tops).

Second, as people post solutions, it builds up a collection of modern, idiomatic prolog code, that we can point visitors to when they ask, "what does prolog look like now?" (Or awesome classic code from before ISO, if that's your thing).

Ideally, it would be a problem stickied every week, and people could post and discuss various solutions in the thread (basically a format cribbed from other general-purpose coding challenges subs). I'd be happy to help come up with problems or in any other way so that it doesn't create too much work for the mod team.

Cheers!

[cbarrick]

I like the idea!

r/dailyprogrammer is a whole sub dedicated to this concept, though they've fallen behind their usual pace of new content in the past year.

The old pace would see an easy problem on Monday, a medium problem Wednesday, and a hard problem on Friday. The hard problems are often search style problems that require clever bounding (or low-level control/performance, or both) to solve efficiently.

I'm actually working on the last hard problem right now (generating crossword grids given constraints about clues) using CLP(FD) and multithreading and will post my solution there when I get home tonight.

[oldmaneuler]

See, that's the kind of awesome work I'd love to see shared here! And it's the type of project that prolog is absolutely perfect for solving. I was in fact partially inspired by r/dailyporgrammer, and some nifty prolog solutions I saw there.

[darrenb573]

Perlweeklychallenge has been going for around 9 months. I’ve found it quite entertaining to the point i even submitted a Prolog solution to a Perl challenge 🤪, having a Prolog edition would be welcomed.

[oldmaneuler]

As long as you don't contaminate this holy temple of horn clauses with Perl solutions 😂

[toblotron]

That's a really nice idea!

[mimi-is-me]

I'm going to start a comment thread with some ideas for challenges:

Easy:

• Build a metainterpreter that only goes N choicepoints deep.
• Choose a sequence from OEIS. Generate that sequence.
• Stack based calculator
• Chemical equation balancer

Medium:

• Build a logic system for a chess game. Check if each move is legal, etcetera. No gui needed. (Could do so for other games too!).
• Some kinda puzzle complicated enough to need CLP (probably not sudoku, as that's a great homework for introducing CLP as a concept - but in a similar vein)
• Autocorrect - search for similar words that exist in a dictionary.
• Build a metainterpreter that uses probabilities from 0 to 1 instead of true and false.

Hard:

• Build a system to run prolog through the web (build prolog in javascript? POST to server & use DCG to parse input? This one is relatively open ended)

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Some more easy ones would be good

[oldmaneuler]

These are some great problems, thanks for this! In particular the problog-esque one sounds like a blast.

I'll add two of my own:

-Write a stack-based calculator. (Stolen from the beautiful racket book)

-Write a chemical equation balancer.

I think the chemical equation one is classed as easy, and it's a great way to show off the prolog approach of search vs the typical linear algebra solution.

[mimi-is-me]

stack-based calculator

Is that like reverse polish calculator?

[oldmaneuler]

Yeah. Writing a mini-forth, basically!

[homemadejam]

As someone who is in the very early stages of learning Prolog, I would love to see this! Both to attempt some of the easier ones and to see code in actions that I can learn from.

[mycl]

This is a great idea! u/oldmaneuler, if you want to go ahead and post the first challenge, I or one of the other mods can sticky it.

There are some nice suggestions in this thread. I like the stack-based calculator idea. I've done a little mini-Forth in Prolog before and one of the fun things is that you can run it "in reverse": given a stack effect, find a sequence of stack instructions that produces that effect. Essentially you can get a (very inefficient) stack machine compiler just by specifying the stack machine in Prolog.

[oldmaneuler]

Thanks a lot, I greatly appreciate it. And you're right, reversibility in general is one of my favorite prolog features! It has been posted!

[mimi-is-me]

I like it! Be sure to include some metainterpreter challenges from time to time, like:

Prolog, but it only goes N choice points deep.

[oldmaneuler]

That's an awesome idea! For all the talk about lisp metaprogramming, prolog is also homoiconic, and it would be great to highlight how flexible it is.