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On February 23 2018 03:55 sabas123 wrote:Show nested quote +On February 22 2018 23:04 Excludos wrote:
So (I might have mentioned this earlier) our firm doesn't really have any testing policy. Our only testing is done in the form of manually checking that shit works after coding. While this will work to some extent, it's not a super good practice.
So one of my colleagues came up with the idea to run a workshop with everyone to teach people how to set up proper tests and to apply some good practices. The conversation with the boss went as follows:
"No".
"Why not?"
"We don't have time right now".
"When will we have time for this?"
"Well everything is a bit unstable at the moment. If we get everything more stable then we'll have ti-" "DO YOU NOT SEE THE PROBLEM HERE?!" Aaaahhh, I remember having a similar conversation once. Good times....
Haha, I remember stuff like that too in one of the companies I was working at.
"Hey boss, you know this 10 years old system that we have to maintain and it's a complete nightmare?"
"Sure, what of it?"
"Well, we did gather all the guys and debated about rewriting it in new technologies to clean up the code, get rid of technical debt and make adding new features significantly easier"
"How long would it take?"
"We could do it in about 6 months"
"No way! Instead of doing that focus on adding this new little feature"
Adding new feature took us 7 months (it was something that shouldn't really take more than a week or two). Technical debt is a bitch.
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Well, when developers say they can do something in 6 months it usually takes more than a year in the end...
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Are any of you familiar with generators/co-routines? I don't have a full picture of what is going on here, and I am wondering if my intuition about them is correct.
If I am DFS traversing a graph with a generator, can I pause the generator and add edges to the graph and then continue the generator, thus increasing my efficiency vs adding edges and starting DFS traversal all over?
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On February 26 2018 15:33 travis wrote:
Are any of you familiar with generators/co-routines? I don't have a full picture of what is going on here, and I am wondering if my intuition about them is correct.
If I am DFS traversing a graph with a generator, can I pause the generator and add edges to the graph and then continue the generator, thus increasing my efficiency vs adding edges and starting DFS traversal all over?
Not entirely familiar with the "generator" part. Is that like creating a representation of the node structure or something?
But, I don't particularly see a reason why you couldn't add edge nodes while traversing. Have your conditions built into the DFS, and then make sure to include the new nodes in the search after creating them.
It would be slower than a straight DFS, though, if that's a problem with efficiency.
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On February 26 2018 15:33 travis wrote:
Are any of you familiar with generators/co-routines? I don't have a full picture of what is going on here, and I am wondering if my intuition about them is correct.
If I am DFS traversing a graph with a generator, can I pause the generator and add edges to the graph and then continue the generator, thus increasing my efficiency vs adding edges and starting DFS traversal all over?
What do you mean "pause" the generator? I am assuming with generator you mean python generators. If there are other types of generators that work differently, then this obviously doesn't apply.
In the case of pythonic generators, there *shouldn't* be a problem (obviously depends on how you implement your generator), but for any algorithm looping over the generator, this *might* cause unexpected behaviour. The first thing is that you don't pause (or run, for that matter) a generator. You usually loop over it, but there are other ways of calling it (such as calling list() on a generator, which internally works out to about the same as doing [x for x in generator], although I'm not sure whether it is coded like that).
Either way, a generator is built with a function that instead of returning a result, it "yields" a result. How you define that function is up to you. If your function is required to know the entire structure of the tree in order to yield nodes, then it will break if you add nodes or edges. If, however, it simply runs the DFS algorithm in each node and yields the next one, then it will not care that you add edges. I don't think you can remove edges without breaking it, though. Adding nodes will lead to these nodes not being iterated over if you don't add edges to unvisited nodes. Moreover, if what you do in your algorithm depends in any way upon the number of edges there, then adding (or removing) edges will lead to incorrect results if you change the structure while running it.
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On February 26 2018 15:33 travis wrote:
Are any of you familiar with generators/co-routines? I don't have a full picture of what is going on here, and I am wondering if my intuition about them is correct.
If I am DFS traversing a graph with a generator, can I pause the generator and add edges to the graph and then continue the generator, thus increasing my efficiency vs adding edges and starting DFS traversal all over?
Yes, but it will be better to use an non-recursive DFS (preferably the non-stack version) as it will run much faster and you will have better control of the logic.
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in Unity, is it possible to select an object that I custom made, drag the outer edge or the corners with my mouse to make it longer or taller? If it is, what would the code look like in C*? It would be very helpful as I make my game.
Also does Unity come with its own platform objects of various shapes and sizes or do I need to make my own and do all the coding myself like not be able to pass through a platform etc...
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On February 28 2018 05:51 Programmer2 wrote:
in Unity, is it possible to select an object that I custom made, drag the outer edge or the corners with my mouse to make it longer or taller? If it is, what would the code look like in C*? It would be very helpful as I make my game.
Yes, this should easily be possible. You need to capture the mouse position on the edge and if clicked -> object.transform depending on how far it moves from its original target. I'm unsure on the exact implementation of this
Also does Unity come with its own platform objects of various shapes and sizes or do I need to make my own and do all the coding myself like not be able to pass through a platform etc...
I genuinely have no idea what you're asking here.
I'm sure there's other people here who's dabbled with unity, but Unity already has a gigantic community with guides, forums, chats, videos, examples, etc etc. I'm sure you'll have a lot more luck if you look around a little bit or ask there 
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I think he's asking if Unity has a built in engine for collision detection. Don't know that myself.
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On February 28 2018 07:52 WolfintheSheep wrote:
I think he's asking if Unity has a built in engine for collision detection. Don't know that myself.
That's a weird question tho considering collision detection is one of the main components of Unity..
Again though I should emphasize that if one wants to learn Unity, there are hundreds of guides on how to get started. Look around on the "learn" tab on Unity's own website https://unity3d.com/learn for instance. The "roll a ball" tutorial is a really good way to get started. I'm unsure about the interactive tutorials as I haven't tried any of them myself, but that sounds like a good idea too! Unity is perhaps the least complicated engine to make anything in, but that doesn't mean you can just jump into it and expect to immediately understand how it works.
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So, let me get back at you with regexes...
/\A(?!(?:com[0-9]|lpt[0-9]|con|nul|prn|aux)(?:\.[^.]*)?$)([w \-.()+]+[w \-.()+])(?<!\.)\Z/i
How can I avoid catastrophic backtracking with long strings (40+ characters) where failing condition appears near/at the end of the string? Trying to test such strings on my dev machine (Core i7 with 12GB of RAM) kills the machine...
I guess I could potentially split it into 3 separate regexes and check each one at a time.
Edit:
Interesting read on the topic: http://www.rexegg.com/regex-explosive-quantifiers.html
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Hyrule19199 Posts
what happens if you switch it around and use a negative match instead of negative lookahead (or positive lookbehind)?
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Are you sure Regex is the right tool for the job?
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That is one hell of a regexp.. How long did that take you to churn out? O.o
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Just recomended a overkill tool for the job. Plz ignore.
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I have a P/NP question.
I have read that were any NP problem be found to have a polynomial time algorithm, then we can reduce any other NP problem to a form where we can use our first algorithm to solve the new NP problem in polynomial time as well.
I don't see why this is the case.
Example: Hamiltonian Cycle problem, and Traveling salesman.
Were I to find a polynomial time algorithm to determine the existence of a hamiltonian cycle in a graph, I still don't see how this could let me find a TSP tour in an upper bound of polynomial time. The amount of subgraphs we would have to iteratively check for a hamiltonian cycle is often exponential.
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On March 01 2018 15:37 travis wrote:
I have a P/NP question.
I have read that were any NP problem be found to have a polynomial time algorithm, then we can reduce any other NP problem to a form where we can use our first algorithm to solve the new NP problem in polynomial time as well.
I don't see why this is the case.
Example: Hamiltonian Cycle problem, and Traveling salesman.
Were I to find a polynomial time algorithm to determine the existence of a hamiltonian cycle in a graph, I still don't see how this could let me find a TSP tour in an upper bound of polynomial time. The amount of subgraphs we would have to iteratively check for a hamiltonian cycle is often exponential.
TSP isn't NP-complete. At least not the most common way of defining it (shortest path). To make it NP-complete, you'd have to ask a different question: is there a route that visits all cities exactly once with distance L or less? This check can be done in polynomial time, so this question is NP-complete.
Now I'm not sure how this would get reduced to the Hamilton cycles problem, but given that it's np complete, I'll assume there's a way to take a polynomial time algorithm and an oracle that solves the Hamiltonian cycles problem, and gives you the answer to the above question. And that doesn't mean you can solve the NP-hard problem of finding the shortest path that visits all cities exactly once with that same algorithm, because this subtly different question is far harder.
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On March 01 2018 06:28 Excludos wrote:
That is one hell of a regexp.. How long did that take you to churn out? O.o
Took me a day or two. It's a regexp that checks if filename will be valid on Windows. We are using it in our model validators and thankfully we haven't run into catastrophic backtracing yet but that's only thanks to other validations failing before reaching this one.
If anyone needs cool regexes I have more of them
VALID_FILENAME = %r{\A(?!(?:com[0-9]|lpt[0-9]|con|nul|prn|aux)(?:\.[^.]*)?$)([w \-.()+]+[w \-.()+])(?<!\.)\Z}i
VALID_PATH = %r{\A(?:[^\/:*?"<>|\r\n\t\f\v]*\/?)+\Z}i
DNS_COMPLIANT_NAME = %r{\A(?![-.])(?!.*\.\.)[a-z0-9\-.]{3,63}(?<![-.])\Z}
VALID_IP_ADDRESS = %r{\A(?:(?:[0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}(?:[0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\Z}
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Question is, if only because a regexp exists, it also should be used...
That's pretty much like the fabled "^.?$|^(..+?)\1+$". (checks if a number is non-prime) And I have seen people seriously use that one, because "look, how cool it is, I have a prime check in only one line!!! This must be the most efficient thing ever". Hint: It isn't.
But hey, only because Mythbusters have proven that duct tape is all you will ever need to survive any kind of situation, it doesn't mean you should sell all your belongings and invest it all into duct tape.
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EPT
