The 2nd Monitor

Jeroen Vannevel

12:06 AM

I so don't like Spring

Stuff is connected through annotations but it's so hard to tell what ones are what

Donald.McLean

12:24 AM

@Corbin Almost every time I try to program in weakly typed languages, I end up crashing and burning.

Captain Obvious

0

Q: JavaScript: Making an array editable by user?

What I want to do: 1: Let users add data to an array through an input field and add button. HTML: <body> <input type="text" id="input"> <button type="button" id="btnAdd">Add Number</button> <div id="outputBox"></div> JS: <script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquer...

rolfl

@Donald.McLean I need the structure and discipline to avoid the surprises later.

I hate having to think-like-the-interpreter in order to simply read the code.

Corbin

12:44 AM

@Donald.McLean really? I've never had problems with it, it just feels dirty. I suppose I do find myself having to refactor weakly typed languages far more often though :/

Donald.McLean

And assembly, which I am completely hopeless in.

nhgrif

Speaking of typing... I was thinking about developing a library of Objective-C collection objects that allow you to specify what type of object you're putting in it and prevent you from putting other kinds of objects in the collection.

Donald.McLean

It's even better when it's enforced at compile time. :-)

Jeroen Vannevel

@nhgrif generics?

nhgrif

Hmm?

Jeroen Vannevel

12:54 AM

@nhgrif Does Objective-C not have generics?

nhgrif

I'm not really familiar with generics. I know it's a term from C++ and Java, but I'm not sure what it'd be in ObjC.

Objective-C has NSArray which holds pointers to objects.

Jeroen Vannevel

@nhgrif It's exactly as you describe; Dictionary<string, int> can only have string keys and integer values

nhgrif

Which means it holds a pointer to any type of object... which means you can make no guarantee about what kind of object is in the array.

Jeroen Vannevel

Oh, it's a dynamic language apparently

Is there a reason why you would do <script src="${jquery_url}" type="text/javascript"><jsp:text/></script> instead of <script src="${jquery_url}" type="text/javascript"></script>?

(aka: omitting <jsp:text/>)

nhgrif

1:13 AM

dynamic binding, not dynamically typed though

Mat's Mug

1:31 AM

hi!

rolfl

Hi ..?

Dagg Nabbit

@JeroenVannevel probably a hack to get the script element not to self terminate

Jeroen Vannevel

@DaggNabbit alright, thanks

Dagg Nabbit

np, just a wild guess, haven't looked at jsp in years

Captain Obvious

2:02 AM

0

Q: New CSS grid at 1800px

Background We have to cater to large screens. So I created this portion of a grid system which is shown to users with screens larger than 1800px. Solution This grid is 1800px wide but can shrink down to 1200px, has 8 columns. I wanted 10px margin around the sides of each column. So I arrived at ...

html css

Phrancis

2:47 AM

Hello again guys

Phrancis

3:39 AM

Can someone briefly glance over the end of my answer to make sure my PHP syntax is OK? Edit as needed. Thanks! codereview.stackexchange.com/a/51962/42632

Captain Obvious

0

Q: Move update_attributes into class and check for non-nil params to update only

There are a number of things wrong with the code here: @cust = Customer.find_by_id(params[:customer_id]) upd = @cust.update_attributes({:city_id => params[:city], :zip_code => params[:zip], :first_name => para...

ruby refactoring ruby-on-rails

Mat's Mug

3:57 AM

the more I read this question, the more I find it's off-topic / non-working code:

5

Q: Get distinct combinations of numbers

The below code returns all distinct combinations based on the logic that 1,2,3 = 3,2,1 = 2,3,1, so it only returns 1 instance of that set of numbers. public void GetPowersets() { List<int> ints = new List<int>() { 1,2,2,3,3 }; var results = GetPowerSet(ints); List<...

c# optimization linq memory-management combinatorics

if I read this right, the quoted block is the desired output. OP's code doesn't produce that.

Phrancis

@Mat'sMug we chatted about that earlier today and kind of had the same impression... Seems like this should be on SO not CR...

Mat's Mug

yeah... I think I originally misread the post, it's not very obvious what's being asked for here

rolfl

Hi, just checking in, code is right, and it should not produce the same results as the quoted-block

Let me rephrase that...

The code shoud not return the same content as the quoted block.

The quoted block is unique combinations.

He wants to change it so that the unique no longer applies.

Mat's Mug

code returns 15 values (lists of values actually) whether the input is new[] {1,2,3} or new[]{1,2,2,3,3} - so that's correct?

rolfl

no....

Mat's Mug

4:08 AM

rolfl

Someone needs to point out that counting in binary and and combinations, are best friends

Mat's Mug

I'm hitting a wall with this code, I've never written something like this (permutations), my head is about to explode... I think recursion is the correct way to do this, but I just can't seem to get it. Trying to implement it with yield return.... not working :(

rolfl

No... you're doing it wrong, but I am no good with C#

There's a trick.

It's the fastest way to do it, and it will work with yield nicely

Let me explain .... you listeneing?

@Mat'sMug ... ?

Mat's Mug

sorry.. yeah

(wife just arrived)

rolfl

Combinations:

- you have a set of numbers.

put them in an array

Mat's Mug

4:15 AM

new[]{1,2,3}

gotcha

rolfl

each number is either in the combination, or it is not.

Each number has a 'state', on, or off.

Now, that reminf you of something?

Mat's Mug

hmm allright

rolfl

Yes, bits.

Consider your numbers {1,2,3}.

Now consider binary counting with 3 bits:

To get combinations, you create an integer that logically has as many bis as data memebers....

int limit = 1 << size

Mat's Mug

so... this isn't about recursion at all?

rolfl

for (int i = 0; i < limit; i++) {
    for (int bit = 0; bit < size; bit++) {
        if (i & (1 << bit) = 1) {
            .... then array[bit] is in the combination

Mat's Mug

4:18 AM

right

and if it is in the combination, you yield return it

rolfl

Not quite.

You need to do that inside the i loop, not inside the bit loop.

So, before the bit loop you create a list to store your combination.

then add the data to the list inside the bit loop.

Mat's Mug

right, because you're yielding an IEnumerable<int> to return an IEnumerable<IEnumerable<int>>

rolfl

then yield the list outside the bit loop

Now, the i loop does not need to be a loop, it can be an int that you use to yield the combination, then you increment it for the next()

in other words, your only state you need is the current i, and the limit.

Mat's Mug

aren't you assuming the values are contiguous here?

Phrancis

I'm going to say my mind is blown and leave it at that.

rolfl

4:21 AM

Array indexes are always contiguous.

Mat's Mug

duh

rolfl

The only time you run in to problems is when you have more members in the set than you have bits in your integer.

Mat's Mug

that seems much, much, much more simpler than OP's O(n^n) solution (making this up, ...but there's definitely an exponential in the complexity there)

rolfl

But, you can safely use a signed 64bit long, and the user will never know even if they have more than 64 set memebers

Because, the yield process is not instantaneous, and, they will have to do it .... oh, about 9,223,372,036,854,775,807 times.

and, they will probably die before that matters.

Mat's Mug

I'm so bookmarking this conversation and eventually implementing it.

bit-shifting stuff always gets me nervous

Phrancis

4:26 AM

I don't understand it but it sounds wicked smart o_O

2

rolfl

Feel free.

Mat's Mug

Q51938

24 mins ago, 23 minutes total – 57 messages, 3 users, 1 star

Bookmarked 11 secs ago by Mat's Mug

rolfl

Combinations are a real problem.... consider a set with just one member.... 'X' how many combinations?

_
X

Now, add another member... Y how many combinations?

_ _
_ X
Y _
Y X

Mat's Mug

but... you don't want to return a "combination" where all "bits" are off, do you?

you should have X, Y, XY and YX... no? (and _ and _ _)

...and _ X and ..yeah that

rolfl

Combinations are different to permutations.

Mat's Mug

4:31 AM

but OP is ignoring the _'s

rolfl

Combinations can contain the empty result

No, he's not.

Mat's Mug

so the 1 output is actually 1, _, _?

rolfl

The quoted block contains just 1, and just 2, and just 3

It is common to not include the empty set result.... but, then you just start your int counter at 1 ... ;-)

Mat's Mug

hold on here..

23 mins ago, by Mat's Mug

OP's ouput also contains it/them

[headsplodes]

I think I'll dream about this conversation

is it normal that I feel dumb now?

Phrancis

So is it where it doesn't display a NULL result where it happens? As opposed to displaying, say, 0 ?

rolfl

4:37 AM

Working some example code here.

Captain Obvious

0

Q: Hackerrank Gem Stones

I am working on some problems on Hackerrank John has discovered various rocks. Each rock is composed of various elements, and each element is represented by a lowercase latin letter from ‘a’ to ‘z’. An element can be present multiple times in a rock. An element is called a ‘gem-element’ if it oc...

python optimization performance memory-management

Mat's Mug

@rolfl you should post an answer to that question, even if the C# is broken - heck, even if it's pseudo-code.

> That was just cosmetics and minor adjustments (some of which may have a positive impact on performance); there's a lot to be said about your algorithm, I'll leave that to another reviewer.

rolfl

    private class Yielder implements Iterator<int[]> {
        private final long size;
        private final long limit;
        private long next = 0;
        private final int[] stash;

        public Yielder(int size) {
            super();
            this.size = size;
            this.limit = 1 << size;
            this.stash = new int[size];
        }
        @Override
        public boolean hasNext() {
            return next < limit;
        }
        @Override
        public int[] next() {

@Mat'sMug Play with it, and provide the answer ;-)

The above is a Java iterator that produces indexes in to a data array.

Mat's Mug

will do! (TTGTB)

rolfl

Each array yielded.... is a unique combination

Mat's Mug

4:49 AM

copied it to a big comment block in Visual Studio

rolfl

Here it is as an ideone with results.

ideone.com/ZoS8QK

Mat's Mug

thanks! and you should get some sleep too!

rolfl

I should.

Mat's Mug

in the meantime..

2

A: Get distinct combinations of numbers

Pasting your code exactly as is into my IDE, ReSharper gives the following warnings and suggestions: List<List<int>> returnResult = new List<List<int>>(); Use implicitly typed local variable declaration I'd also rename returnResult to just result, so: var result = new List<List<int>>()...

ok gone

Phrancis

I have to say, @rolfl you seem to know your shit, across multiple languages, platforms, etc. I am quite impressed

rolfl

4:59 AM

Yhanks, I would like to say I am brilliant, but, no, I have just been around the block ... ;-)

almost 20 years at this now.

and, I 'grew up' at a time where you had to conserve each cycle

@Mat'sMug - for the record, the complexities for the algorithm I have shown you is size-complexity O(1), and time complexity O(n2^n)

where n is the number of members in the set

That ime-complexity can be rephrased as O( 2^(n+1) )

which is huge, but is still as good as it gets.

Phrancis

5:13 AM

Impressive still!
I can't get DB2 Express-C to install on my machine, grr. May have to contact IBM.

DBI1189E There has been an attempt to use db2_install on an image for a platform that does not match the current platform 'MacOS' on which it is being run.

Guess I'll mess with that ~~tomorrow~~ later today.

Captain Obvious

5:30 AM

0

Q: resize renderer on browser window size change

For a game, there is some WebGLRenderer object that wraps around canvas element. There is need to update it's size when browser window size changes. Here goes my current code written using BaconJS. What do you think about it ? Would you improve it in any way or maybe do it other way? I have read ...

javascript coffeescript bacon.js

Dagg Nabbit

7:34 AM

function combos(a) {
    for (var n = a.length, i = 1 << n, r = []; r.push(s = []), i--;)
        for (var j = n; j--, i & (1 << j) && s.push(a[j]), j;);

    return r;
}

Captain Obvious

7:55 AM

0

Q: Two solutions with min max values which should be slower?

While practicing at codinbat.com on the assignment Given an array length 1 or more of ints, return the difference between the largest and smallest values in the array. Note: the built-in Math.min(v1, v2) and Math.max(v1, v2) methods return the smaller or larger of two values. I wrote a solutio...

java array

Captain Obvious

8:33 AM

0

Q: bind and unbind clickoutside event

I have a Jquery dialog that is opened when the content of a div is clicked. When the dialog is opened, I am binding a jquery outside event so when the user clicks anywhere outside of the dialog the dialog is closed. When the dialog is opened I am modifying the URL path with history.pushState(s...

Q51938

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