The Big Programming Thread - Page 793

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Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
2. No recruiting for your cockamamie projects (you won't replace facebook with 3 dudes you found on the internet and $20)
3. If you can't articulate why a language is bad, don't start slinging shit about it. Just remember that nothing is worse than making CSS IE6 compatible.
4. Use [code] tags to format code blocks.

waffelz

Germany711 Posts

November 04 2016 15:31 GMT

#15841

On November 05 2016 00:26 tofucake wrote:
The big power draw is the motor that will do the locking/unlocking. Wifi dongles are relatively low-power.

Sorry, i misunderstood. I will rephrase my post, the cupboard won't be properly locked, the device does nothing more but shout at the intruder. It really will be just a gimmick/reminder to the flatmantes to ask first.

tofucake

Hyrule19222 Posts

November 04 2016 15:33 GMT

#15842

Ah, well then that changes things. Shouldn't be too difficult to make then. An arduino can run something like that fairly easily on a few batteries for probably a week or so.

Acrofales

Spain18325 Posts

November 04 2016 15:41 GMT

#15843

On November 05 2016 00:33 tofucake wrote:
Ah, well then that changes things. Shouldn't be too difficult to make then. An arduino can run something like that fairly easily on a few batteries for probably a week or so.

This. I'm also not quite sure why wifi is required at all if all it needs to do is play a sound when someone opens the cupboard. If it is, I am not sure why the IP would be reset ever. When you set it up, just reserve an IP for the device on the router. Even cheap and shoddy ones you get with your internet subscription offer that functionality (at least here). It's one of the very very basic things in DHCP setup.

tofucake

Hyrule19222 Posts

November 04 2016 15:46 GMT

#15844

He wants it controlled by an app, which is why I was thinking wifi, because I doubt there's an ethernet port inside the cabinet

waffelz

Germany711 Posts

November 04 2016 15:47 GMT

#15845

On November 05 2016 00:41 Acrofales wrote:
This. I'm also not quite sure why wifi is required at all if all it needs to do is play a sound when someone opens the cupboard. If it is, I am not sure why the IP would be reset ever. When you set it up, just reserve an IP for the device on the router. Even cheap and shoddy ones you get with your internet subscription offer that functionality (at least here). It's one of the very very basic things in DHCP setup.

I was talking about a reset of the external IP. In Germany it is quite common for your external IP to reset every 24h, as long as it isn’t cable. I don't have much more information about the router but they will probably change provider anyways. If I am lucky, they end up with the same router that I have which will makes things much more easy to me, even though it isn't great either. So the IP problem isn’t about internal network communication.

Acrofales

Spain18325 Posts

November 04 2016 15:50 GMT

#15846

On November 05 2016 00:47 waffelz wrote:

Show nested quote +

Why does the external IP matter? Or does he want to be able to control his cabinet from outside of the LAN? If so, there's things like dyndns (I think that still exists) which get around the problem (just set up a cronjob to update the dns every time your lease expires).

waffelz

Germany711 Posts

November 04 2016 16:10 GMT

#15847

On November 05 2016 00:50 Acrofales wrote:
Why does the external IP matter? Or does he want to be able to control his cabinet from outside of the LAN? If so, there's things like dyndns (I think that still exists) which get around the problem (just set up a cronjob to update the dns every time your lease expires).

Yeah, but that’s the kind of stuff I only can really consider when I am sure about the hardware I am dealing with, both in terms of arduino/raspberry and router (my former router had a free subscription to dyndns service as well as an build in support for it. very convenient times back then. At least all the dyndnsservices I used after that aren't free anymore). At the moment the main crux is choosing between arduino/raspberry/possible third alternatives I don’t know about.

Manit0u

Poland17774 Posts

November 04 2016 16:23 GMT

#15848

On November 04 2016 23:41 mantequilla wrote:

Show nested quote +

On November 04 2016 22:29 Manit0u wrote:

On November 04 2016 20:00 mantequilla wrote:

On November 04 2016 19:21 Nesserev wrote:

On November 04 2016 18:37 mantequilla wrote:
I'm a web app developer (from scratch with code) but got suggested using a cms for a customer with simple needs, they need to make announcements etc on their website, some static info and links to other systems. I'm alien to whole cms thing.

when I'm making a website for a customer using a cms, am I supposed to write code regularly? Is the online content editing thing for the non technical customer to just update the site content?

I quickly tried to put a language selector on top of the main page using couple of cms'es, and they suggested me to write server side code (jsp) to put it there. I thought I'd be just drag-dropping a ready lang selector component on the online page

There's usually a lot of content on a website that the owner of a website should be able to change without the intervention of any web developer; a CMS provides the interface that allows him/her to do this.

Does it make sense that a web developer has to be contacted every time you want to add a post on a blog, change the banner of your website, etc.? - No, so that's why you use a CMS. Not just for simple websites, but for almost any website.

If the question to "should the owner be able to change this?", you need a CMS.

And it's not just for the owner, even the developer can benefit; sometimes it's the most convenient to hook something up to the CMS beforehand, instead of manually changing it in the HTML later on.

I know-understand when a cms is needed, that wasn't the thing I was trying to ask. I wanted to ask how much programming is involved with me. Am I supposed to write code regularly, or is it a rare task only needed with advanced cases? I never worked with them so have no idea what the usual workflow is :/

It depends on client demands. If you're not OK with just using some existing CMS and its out-of-the-box features than you can expect plenty of coding on your part to incorporate the necessary stuff into the CMS. But usually after you ship it you rarely have to touch it.

The programming work involved can be anything from a couple of days to a couple of months.

the chapter 1 of liferay book teaches how to checkout code and install ant etc. first page in opencms documentation talks about writing jsp. confused

Show nested quote +

job is to create a simple website using cms that:

- has multiple locales selectable
- has an announcement feature where owners can make announcements which shows on main page
- have some links to external websites

http://octobercms.com/features

Thaniri

1264 Posts

November 05 2016 05:12 GMT

#15849

+ Show Spoiler +

I'm working my way through project euler in Java, I've done 6 problems so far. I'm stuck on problem 3 though:
projecteuler.net

+ Show Spoiler +

public class ID3 {
	
	public static void main(String[] args) { 
		findFactors(600851475143);
                sieve(600851475143);
	}
	
	public static long findFactors(long input){
		//won't accept long as an input
		
		return 1;
	}
	
	public static long[] sieve(long input){
         //this is just a copy pasted sieve of eratosthenes
		
		long[] primes = new long [numberOfPrimesFound];

		return primes;
	}	
}

My plans are this:
- Find the primes up to 600851475143 then check if they are factors in descending order.
or
- Find the factors of 600851475143 and then check if they are primes in ascending order.

Neither plan will work due to the size being above the range of an int.

I cannot declare a long array because that'd be stupid according to stack overflow (need 16gb of memory) and my findFactors method won't take a long as an argument, however I can't google an answer as to why.

Anyone have an idea for a better plan or how to make an argument accept a long as an input?

I'm trying my best to not just google the answer, though I admit I copied the sieve from stack overflow.

edit:

http://pastebin.com/rdH9H1cM

BigInt isn't working either.

I'm an idiot:

600851475143L allows long to be used as an argument

Blisse

Canada3710 Posts

November 05 2016 05:54 GMT

#15850

You have to add an 'L' to a number to mark it as a long.

findFactors(600851475143L);

edit: nice

Thaniri

1264 Posts

November 05 2016 06:24 GMT

#15851

http://pastebin.com/ncE1ZjxS

Unfortunately BigDecimal doesn't allow for comparison operators, I think I'mma have to sleep on this one. I might have to create my own method that compares two BigDecimal numbers.

edit: I think posting things online instantly allows me to find the answer. Guess what? BigDecimal has a compareTo() method.

What I'll do is ask a mod to let me post in this thread but "shadowban" me like on reddit so no-one else sees my posts. Thus I will get the answers and not bother anyone.

phar

United States1080 Posts

November 05 2016 17:31 GMT

#15852

Don't sweat it. What you are doing is called rubber duck debugging. It will never go away, even in industry.

phar

United States1080 Posts

November 05 2016 17:37 GMT

#15853

On November 05 2016 01:10 waffelz wrote:

Show nested quote +

How long does it need to be powered for, with what power source (battery? How big?). This could greatly affect your choice of underlying device ... a raspberry pi or even the tiny arduino may not last all that long on battery.

Wrath

3174 Posts

November 05 2016 19:45 GMT

#15854

Can someone be nice and guide me to a good resource to understand MVC architecture? I feel really lost. Also, it would be really really cool if it contains a small project to practice the MVC architecture, it will help to understand it if possible.

RoomOfMush

1296 Posts

November 05 2016 20:16 GMT

#15855

On November 06 2016 04:45 Wrath wrote:
Can someone be nice and guide me to a good resource to understand MVC architecture? I feel really lost. Also, it would be really really cool if it contains a small project to practice the MVC architecture, it will help to understand it if possible.

Its just a simple concept of how to structure your classes in OOP. There isnt much to it. A "simple" example for MVC isnt of much use though. The concepts benefits only really come to light in bigger applications where well separated layers make maintenance and extension more comfortable and less error prone.

BluzMan

Russian Federation4235 Posts

November 05 2016 22:49 GMT

#15856

Well, try this for starters:
blogs.msdn.microsoft.com

And keep in mind that there ain't actually a common understanding of what modern MVC really is. The abundance of views on the topic can get really confusing at times. What everyone agrees upon is that there is a definite advantage to be gained from separating application logic and the way user interacts with it (both input and output), hence the M-V pair which is present everywhere. A neat way to separate that is ask yourself: "how much of the application can I package as a command-line app in a way that the application data can be displayed in any way thinkable?" then make that your model. The rest will be your VW (View Whatever). The third "magic component" is understood differently everywhere so just consult your platform's documentation to clarify (iOS has one way to look at things, Qt has another etc). It's best to always understand what exact problem your patterns are solving and adapt them accordingly. For instance, our team has a cross-platform mobile app which is mostly written in C++, but uses platform code for UI, so our views end up being extremely dumb (to keep as much code as possible in the cross-platform part, we don't even allow Swift classes to handle user taps on their own) which is I guess an example of a "Model View PresentationModel" pattern from the article, but there isn't any magic in that besides solving an exact problem we have.

Birdie

New Zealand4438 Posts

November 05 2016 22:52 GMT

#15857

There are also quite a lot of variants/interpretations of MVC.

The best way I found to understand it is that you have three groupings of classes: the group that controls your database, the group that does any logic, and the group that controls the interface. The group that does logic is the glue between the other two groups.

The general path of information is that the user interacts with the interface; this triggers a call to some logic in the logic group, which often but not always then calls for some data from the database group. Then the logic group send the data to the interface group which displays it.

However, some will disagree as to how MVC this is; some versions have the model doing a lot more logic, other times the model and controller are combined and basically only the view is extracted, and so on.

EDIT Just saw BluzMan's post, pretty much better summary of the variations/interpretations than I gave.

Blisse

Canada3710 Posts

November 06 2016 00:24 GMT

#15858

http://pastebin.com/bJraUvyK

if anyone can help a little bit, i'm doing hackerrank's synchronous shopping.

https://www.hackerrank.com/challenges/synchronous-shopping

i have a solution but i can't get it to run fast enough for all inputs. my breadth first search is too slow :/ if anyone could take a look, i'd appreciate it. the slow method is synchronous_shopping(path)

things i've tried:

using list as underlying container for queue
using a 1D array like a 2D array

slmw

Finland233 Posts

November 06 2016 02:26 GMT

#15859

Usually in competitive programming you should look for optimizations that make your code faster by an order of magnitude. You can simply look at the asymptotic runtime of data structure operations to estimate whether it is good enough, e.g. changing a list to a queue won't change pretty much anything.

Did you try to calculate approximately how many times your algorithm will check a node in a worst case scenario? How useful is the condition on line 117 if you assume the input is designed by your worst enemy? Is BFS the best algorithm for path finding in a graph with variable edge costs?

If you want to know the answer:
+ Show Spoiler +

Use Dijkstra's algorithm. Only process a pair (shop, bitmask) once, since the first time is guaranteed to be the cheapest way to reach it. My solution.

Blisse

Canada3710 Posts

November 06 2016 04:35 GMT

#15860

That feel when you started from Dijkstra's and way diverged because you weren't getting the right answer :'D Thanks a bunch slmw :3 I don't do much competitive programming.

edit: I've been doing the find min for Dijkstra's wrong my entire life - priority queue.... T_T

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