The Whiteboard

user55340

1:40 AM

@overexchange Have you actually tried implementing it? Copy it into your IDE and write class Foo implements Interface and see if it works. See if the IDE demands additional methods be added. See what those methods are. It is much easier to try for yourself than asking in chat.

user55340

I would also strongly encourage you to read:

user55340

13

A: How to ask "how to understand some code" questions

Often these questions are closed. In days of old they would have been closed as "not a real question" or "too localized." The reasoning behind this is that there isn't really anything that one can answer definitively and draws upon our expert knowledge as a programmer. Furthermore, there are an...

user55340

> These questions of "explain this code to me" is very much akin to someone coming up to you, handing you a picture and saying "I don't understand this. Could you describe what you see here?"

There are so many possible options for someone to describe. We could describe the process of drawing (and you can see the sketch marks from previous revisions). We could describe the elephant itself and its form. We could describe the technique (and if we think its good or bad). The possibilities are endless.

user55340

1:53 AM

-2

Q: Interpolation search with strings, how do I calculate probe_index?

As far as I know Interpolation search is binary search except instead of the calculation: probe_index = low_index + (high_index - low_index)/2; you use probe_index = low_index + Ceiling( ((targetKey - A[low_index])/ (A[high_index] - A[low_index])) * (high_index - low_index) ) for a sorted arr...

user55340

The strings need some padding... the data file format is:

user55340

AALEN	DIANE	ELIZABETH		9	4	1950	F	HARRIS

user55340

So that makes sorting to make sure that comes before:

user55340

AAMODT	SANDY	KAY		10	29	1950	F	DALLAS

user55340

When trying to interpret each last name as a string more challenging. And then there's the first name too.

user55340

1:55 AM

AARON	ANDREW	MARK		3	6	1950	M	DALLAS
AARON	BETTY	LOU	ANN	9	25	1950	F	GALVESTON
AARON	BOBBIE	JOE		11	27	1950	M	GRAYSON
AARON	BRENDA	KAY		12	28	1950	F	BOWIE
AARON	DONNIE	RAY		7	6	1950	M	DENTON
AARON	EDDIE	LEE		10	1	1950	M	BROWN
AARON	GARFIELD		III	11	26	1950	M	HARRIS
AARON	JAMES	HOMER	III	1	23	1950	M	FISHER
AARON	JOE	ALVIN		4	3	1950	M	LIBERTY
AARON	JOHNNY			8	1	1950	M	HOCKLEY
AARON	KAPPIE	FERN		11	4	1950	F	HIDALGO
AARON	LARRY	JAMES		11	12	1950	M	LAMAR
AARON	LINDA	MARIE		6	4	1950	F	MCCULLOCH
AARON	LYNDELL	DIANE		7	12	1950	F	DENTON

user55340

Hmm, looks like the data isn't sorted - why does Lee Richard AaronSON come before Stephen Michael Aaron?

user55340

And, granted I've got a bit of Java-esque design thoughts, I'd read the entire line in, create an object based on it, have a function that computes the ordinal-esque value for the nameS, create some unit tests to make sure that that certain combinations sort properly (so all the X Y Aarons don't have the same ordinal value).

user55340

Maybe do some data analysis on the values first to see what the maximum and minimum lengths of each of the strings are for the current data set. Granted that this is academic code, you can go just on that and say "nope, not getting any other data ever" - real world names are quite problematic.

user55340

And I'll also point out that this is why we, as professional programmers, aren't always the best to ask for academic homework assignments - we may very well be doing things the wrong way or over engineering it.

user55340

Quite frankly, I'd say "screw interpolation sort" and stuff it all in a nice TreeSet. The NavigableSet interface is quite useful.

user55340

2:02 AM

docs.oracle.com/javase/7/docs/api/java/util/NavigableSet.html

user55340

You could do things like Set aarons = data.subSet(new Datum("Aaron","A"), new Datum("Aaron","ZZZZZZ")); // please let there never be someone with a first name that sorts after "ZZZZZZ"

user55340

(and this is why you wish you lived in Iceland)

user55340

Icelandic Naming Committee

The Icelandic Naming Committee (Icelandic: Mannanafnanefnd; pronounced [ˈmanːaˌnapnaˌnɛmt])—also known in English as the Personal Names Committee—maintains an official register of approved Icelandic given names and governs the introduction of new given names into the culture of Iceland. == Composition and mission == The Naming Committee was established in 1991 to determine whether new given names not previously used in Iceland are suitable for integration into the country's language and culture. The committee comprises three appointees who serve for four years, appointed by the Minister of Justice...

user55340

The names in Iceland are an enumerable set.

Duga

3:33 AM

You might have better luck on programmers.stackexchange.com — Rob 27 secs ago

overexchange

class Outer1{
	private static class In1{
		private int i;
	}

	private static class In2{
		void m(In1 in){
			in.i++;
		}
	}
}

Can somebody give me real world scenario that could use such code?

Nick Alexeev

3:56 AM

@overexchange In the real world, your compiler will be disappointed, because you are trying to declare an instance member (in other words, a non-static member) in a static class.

Nick Alexeev

4:25 AM

Folks, is anyone patterns-happy ? I've come across this line:

> Strategy has 2 different implementations, the first is similar to State. The difference is in binding times (Strategy is a bind-once pattern, whereas State is more dynamic). source

The page seems to deal only with one implementation. I can't seem to find out what the 2nd implementation might be. Or, do they mean that State and Strategy are these 2 ?

Ixrec

6:28 AM

@overexchange In the real world I'd never let that through code review. If there is a good reason for structuring code that way, the variable/function/class names involved should be far more self-documenting than those, and you'd probably need comments too to justify that structure over simply having those methods/members on the outer class, or even more simply, having the inner classes exist separately in publicly accessible and easily testable files.

Duga

@Alexander It has more to do with computer science than programming, but is less likely to be known by name to computer scientists, who spend time researching new methods, than programmers, who stick to tried and true methods, hence the question belonging here. Also, I'm familiar with the theory, but after hours of googling I still can't seem to find the function name I am looking for. — TheEnvironmentalist 27 secs ago

Duga

8:43 AM

It's a "too broad" Q&A , try to define which UI component you will use. ( jquery, angular, datatables jq... pure html & css ) . For server side, you can resolve only with .net native code. And... Don't test the patience of this community: You must make the effort to create a piece of code and if necessary create a new question. Check programmers.stackexchange.com for revision code. — Mate 52 secs ago

Duga

10:10 AM

I'm voting to close this question as off-topic because it's not really a programming question. It may fit on programmers.stackexchange.com, check their help centre. — deceze 13 secs ago

user55340

11:46 AM

@NickAlexeev static inner classes are about the relationship to its enclosing class - not about its own instance fields.

user55340

Personally I like inner classes for builders and row mappers because I can access the private fields of the enclosing class directly.

overexchange

12:12 PM

@MichaelT DO java design patterns use mostly nested and inner classes/interface? as far as basis structore is concerned

ratchet freak

@overexchange they are handy but not the holy grail of patterns

maple_shaft

@overexchange Design patterns are above that

inner classes and nested classes are more of an implementation detail of a design pattern where a design pattern is almost a heuristic and not necessarily a scripted solution to any one problem

you need not use them

MetaFight

197

A: Are design patterns really essential nowadays?

For my money, I think everyone's missing the point of design patterns. It's rare that I sit wondering which pattern I should use in a given situation. Also, I was using most of those patterns long before I knew they had names. The power of design patterns is in communication. It is much quicker ...

overexchange

I mean, if you see this below code, Does it belong to some pattern?

class Foo {
	interface Bar {
        void callback();
    }
    public static void registerCallback(Bar bar) { }
    public static void registerCallback1(I i){ }
}

maple_shaft

I can't identify if this is following a design pattern partly because I don't understand what the goal of this Foo class is

nor do I understand what a Bar object is

SOLID (object-oriented design)

In computer programming, SOLID (Single responsibility, Open-closed, Liskov substitution, Interface segregation and Dependency inversion) is a mnemonic acronym introduced by Michael Feathers for the "first five principles" named by Robert C. Martin in the early 2000s that stands for five basic principles of object-oriented programming and design. The principles, when applied together, intend to make it more likely that a programmer will create a system that is easy to maintain and extend over time. The principles of SOLID are guidelines that can be applied while working on software to remove code...

S stands for Single Responsibility

What is the responsibility of the Foo class. If Foo is just an example for a point, can you explain Foo in context?

Can you explain an object of type Bar in context?

What about Template I

@overexchange If you want to identify a design pattern being utilized, it is usually better to start with the problem that is being solved

overexchange

12:48 PM

Foo.registerCallback1(new I(){
			public void f(){

			}
		});

this is callback functionality

Foo.registerCallback(new Foo.Bar() {
		    public void callback() { }
		});

maple_shaft

@overexchange Why are callbacks for Foo functionality static?

user55340

@overexchange I use them that way for convince and organization. Also custom exceptions for Spring controllers and services.

user55340

The key is do what makes sense. Getting hung up on Patterns and the like gets in the way of actually writing code.

user55340

You don't get paid to pontificate on patterns and principles. You get paid for code and results.

Jimmy Hoffa

@MichaelT does Java have generic static classes? Are they segregated by type param so instead of one instance per process, the compiler generates one instance per process per type parameter used?

maple_shaft

1:03 PM

@MichaelT Speak for yourself. I am paid handsomely to sit in an ivory tower and make decisions that will cause developers to decry my name

:)

Jimmy Hoffa

@maple_shaft far too true, far too often. Nice view up there? How're the nose bleeds treatin' ya?

maple_shaft

@JimmyHoffa Better than the nose bleeds of the devs on the ground getting punched up by PM's

^ Me

staring down maniacally from my ivory tower at the little people as I sprinkle my processed crap down upon them

Seriously... look at the guy on that box

user55340

@JimmyHoffa all regular classes are "static" or alternatively "it has no meaning"

user55340

A static inner class can be accessed without an enclosing object.

user55340

new Foo.Builder()

user55340

1:14 PM

If it wasn't a static inner class you would have to have something like...

user55340

Foo bar = new Foo();
Inne qux = new bar.Inne();

user55340

The static inner class means you can access it the same way you access a static method or field.

maple_shaft

Oh Dynamic Programming... why do you make my brain hurt so?

user55340

That's just its nature.

maple_shaft

Question: "Find me the optimal value of treasure that I can fit into a knapsack with a capacity of k"

Jimmy Hoffa

1:20 PM

@MichaelT ?? I asked about static generics, like public static SomeClass<T>

maple_shaft

Answer: "That is NP hard... go F' yourself

Jimmy Hoffa

@maple_shaft optimism sucks, good enough FTW.

user55340

@JimmyHoffa ask me tonight. I need a better chat and ide to explain.

Jimmy Hoffa

@MichaelT O_o it's that complicated? I didn't think Java had anything that different from C#, I'll go look it up m'self now..

oh whoa, Java doesn't have static classes at all; just members and methods

so they don't have generic instance partitioning, that sucks, that's a really useful feature I use in C# rather often

in C# if you have public static class MyClass<T> { ... } and you use in a method MyClass<int>.Foo(); and MyClass<byte>.Foo(); then the compiler actually creates an public static class MyClass~int { ... } and a whole separate version public static class MyClass~byte { ... } where throughout the instance the T is replaced with a hard-coded form

it's handy because you can create type segregated dictionaries and lists and things so that it reduces multi-threaded contention on structures by partitioning them by type requested.

but in Java if you only have methods (stateless) those won't need type partitioning, and instance members can't specify type parameters so those can't be partitioned by type either, so you lose those whole partitioning feature altogether

user55340

As you've just typed away, I need a non-mobile chat to explain.

Jimmy Hoffa

1:31 PM

@MichaelT is my description inaccurate?

user55340

Gotta sit down and read it more in depth.

Jimmy Hoffa

aye

146

A: Static method in a generic class?

You can't use a class's generic type parameters in static methods or static fields. The class's type parameters are only in scope for instance methods and instance fields. For static fields and static methods, they are shared among all instances of the class, even instances of different type para...

yeah no partitioning at all

Ampt

2:17 PM

@maple_shaft Yeah, but with dynamic programming and pre-computed weight tables, it can be done in poly time, which is why dynamic programming is cool

maple_shaft

@Ampt Isn't it just an approximation though?

nvm

NP complete means it can't be done optimally, not that it can't be solved

Ampt

Can't be done optimally in Polynomial time*

but with dynamic programming, you trade input length for time - in this case you precompute the combination tables, and then use a modified algorithm on that, giving you pseudo-polynomial time

maple_shaft

@Ampt that is a very textbook answer there

I am prepping for a Google interview

ratchet freak

until the tables exceed polynomial space

Ampt

you trade time for input length - you cut your time down, but the amount of data you supply in is exponential.

ratchet freak

2:21 PM

then you can get polynomial time with some good hashing ;)

Ampt

@maple_shaft so do you want text-book, or non textbook...?

maple_shaft

2:32 PM

I don't know what I want

I started in Computer Science at school and changed majors to IT

user55340

I Want It All (Queen Rocks)

►

maple_shaft

There is a lot that I either don't know or only have vague familiarity on as far as concepts

^ pretty much this

I am a colossal fraud

user55340

Especially the hair. I mean, who doesn't want that hair?

maple_shaft

This Google interview will be a giant embarassment for me

I can talk through pseudo code of an algorithm but when I try to write code to whiteboard my mind will turn to spaghetti

i have been studying and practicing on hackerrank until 2am in the morning with the same conclusion

I am boned

user41796

@maple_shaft If you feel that strongly, you can always decline the interview

ratchet freak

2:36 PM

@maple_shaft write psuedo on the whiteboard

maple_shaft

@GlenH7 sometimes I get hopeful

but then I try a programming exercise and spaghetti

user41796

"Hey, I've done a ton of research on your interview process, and I've been practicing as a way of preparing. What I'm finding is that my analytical style doesn't align with how you interview. I think you're going to be disappointed in the results, so I'm declining the opportunity to interview with you at this point. I'm going to keep practicing and when I feel more comfortable with this style, I'll be back in touch. Many thanks again for the consideration."

user41796

Heavily technical interviews like that don't work for all styles of programmers

maple_shaft

Arms weak brain spaghetti, spaghetti on my sweater already, moms spaghetti

enderland

To be fair though @GlenH7 that basically self-selects out. That might be true, but... it also might be useful to have them do that than to do it yourself

maple_shaft

2:39 PM

@enderland this

user41796

@enderland I agree. But... there's also a mental aspect. If you go into an interview with the foreboding of it's gonna suck, well, 9 times out of 10, you're going to find out that it's gonna suck.

ratchet freak

@maple_shaft you should try for lasagna instead

user41796

So if you can't clear that mental hurdle and throw your best at it, sometimes it's better to self-select out.

enderland

@maple_shaft then write pseudo code rather than actual code :)

maple_shaft

I want to get in. No doubt. I am just realistic about my chances and where I lack compared to other programmers. I am extremely high level analytical planner. I don't want to embarass myself though

These problems?

user41796

2:42 PM

@maple_shaft So sell yourself on yourself and know that you can sell your higher level skills to overcome any shortcomings with the "grind out code" portions of the interview.

maple_shaft

I can conceptualize the problem, explain potential algos that can be used... maybe even write pseudocode, but I need a search engine to go farther

user41796

And FWIW, I don't know that I would do that well with that style of an interview either. I tend to be slower and more deliberate in analyzing a problem.

ratchet freak

try to get the psuedo as close to actual code as possible

maple_shaft

@GlenH7 Well their interview process is pretty much 5 rounds of 45 minutes to code an optimal solution on a whiteboard

and it should compile

user41796

That's why I don't interview there. :-)

enderland

2:43 PM

I wonder what the median/average age for new Google hires is

ratchet freak

I would tell them I'd need a few minutes to get the typos out of it

blind coding is a pain

maple_shaft

~ 30 i think

ratchet freak

I can do it for SO and stuff but it usually is based on the code in the OP

maple_shaft

I think I am going to conceptualize the approach in natural language, then write pseudo, then if there is time start coding

if they don't like it they can bite me

I am a plan first kind of guy

Jimmy Hoffa

@maple_shaft at least you're having a go at it, me and lots of others don't just because we presume we've no chance. Good on ya for having a go at it regardless of your confidence. Also good on ya for doing the hackerrank stuff and trying to prep. I can't stand all that prep stuff, makes me crazy

maple_shaft

2:52 PM

@JimmyHoffa Implying that it doesn't make me crazy

Jimmy Hoffa

@maple_shaft you're not ranting about asgardian numerical systems inbetween inchoate bellows of rage, you're doing better than me

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