The Neutral Blog

May no question be too silly.

[leonmanrolls-blog]

Everything is a remix.

Without Pioncare, Lorentz and Hilbert would Einstein have formulated special/general relativity? Almost certainly not. Would these men have formulated their theories without those that came before? No. Truly no man is an island. Schooling thumps out of us one of our most important abilities, the ability to copy or 'cheat' as they would have you believe. Having the mentality that one must somehow always come up with answers 'on their own' is wrong on so many levels. It would seem the evolution is most evident in biology but is certainly an idea that has implications outside of that field. If I sat down and tried to do an exact copy of the mona lisa my copy would certainly come out different, even if I was a highly skilled painter it would not come out exactly the same. Thus by copying, something new has been created. As in nature then I postulate that anything that has ever been created is subject to the forced of copying and remixing. These are the tools of the creator. More precisely, imperfect copying and mixing, however this is implied since perfect copying by definition would not have created something new. So then it would seem that the people that we hold in high regard for pushing the human race forward for the most part are analogous to a group of people (the human race) building a tower. This tower offers the playground upon which each generation of offspring shall prove their worth. This process is likely going on subconsciously in most people but that is besides the point. From the tower we can look out across the land for ideas to copy and remix, and we can then add our own little brick to this tower. Many of the bricks appear insignificant, as are the bricks that are being laid in between floors. Every once in a while someone lays a brick that completes a whole floor. Everybody stops and turns in amazement. This person has completed the floor, she has achieved something totally amazing and new that we haven't seen before. This is true, we have a new floor, a new way of thinking, a new paradigm, so on the surface this makes sense. However to completely ignore not just the other bricks but the other floors that had been laid before would be insane. The whole idea of a genius is indeed a seductive one. Malcolm Gladwell of course makes an excellent stab at debunking this myth. The genius myth allows most of the human race to not even bother with attempting to solve the world's problems, or try to strive for excellence. 'I'm not smart/special enough', 'I'll leave this business of making music to someone more talented', and so on. In war, we love tales of brave generals and soldiers who are experts with the sword, cutting through enemy lines with ease, going from battle to battle killing hundreds in their wake and obtaining power and wealth. The reality of war is that battles are in the vast majority of cases won and lost before a single sword has been drawn, before a single shot has been fired. Are your men adequately supplied? Are they going into battle after having marched hundreds of miles on little food or water. Are you on the lower ground. Outnumbered? It is the nature of statistics that these factors will not always cause you to lose a battle, but 99% of the time they will. Even Gilgamesh/hannibal (can't remember) who marched his massive army with elephants from north africa to rome, by the time he got to rome his force was weakened, his ability to keep his army adequately supplied was compromised, they were miles upon miles away from home, they had lost before their first battle. If you approach the issue of being an innovator/inventor/game-changer without the proper mindset, then you have lost before you have begun. If you think you are going to in isolation pull a rabbit out of your hat and be haled as a genius, you are sorely mistaken. You simply must copy, you must take that idea that school has drilled into you that the answer must come from within you and murder it violently *kill it with fire*. While on the subject this way of thinking works in school because you are not being asked to do anything new. You take on some knowledge, and then at a later date reproduce it for a test. This gives the illusion that answer is coming from within you, but it is not. The illusion here is simply the time gap. Ah the illusion of time. We are already dead but for the illusion of time. School is absolutely artificially preventing you from copying for absolutely no reason whatsoever. If i forget how to do integration by parts, I will look it up. If i keep having to look it up my brain will eventually remember it and I won't have to anymore. If i stop using it my brain will forget it, as it should, as evidently I don't need that piece of information anymore. Why should we interfere with this process? Copy and remix. Comix.

[leonmanrolls-blog]

this and jQuery

In jQuery, this will either refer to a DOM element, or a jQuery object. console.log(this); is your best friend for investigating when confused. It will be a DOM element when inside a callback function, such as:

$('something').click(function(){ console.log("Hey I'm inside a callback"); });

When inside your own jQuery functions, it will be a jQuery object. Well this is news to me, we can create our own jQuery functions? What is the difference between creating my own jQuery function and simply creating my own function? What defining your own jQuery function allows you to do is something like this:

$(element).yourfunctionhere();

[leonmanrolls-blog]

Some basic statistics

What is a residual? A residual of an observed value is the difference between the observed value and the estimated function value. This is distinguished from the error, which is the difference between the observed value and the true (unobservable) function value. This is not particularly enlightening. An example would be if we have a population, apparently the mean of the population cannot be known (unless we take the whole population as a sample?) but the mean of a sample of that population can be known. Therefore the mean of the sample is an estimate of the mean of the population. Now the difference between an error and a residual is error means how far a sample is from the population mean and a residual is how far a sample is from the sample mean. Also, the sum of the residuals must be zero within a random sample, I think this implies that if the sum of the residuals is not zero then the sample was not random. That I can stomach. This actually does make sense when you think about taking a repeated measurement. You are only ever taking a sample, you can never know the whole 'population'. The mean of your samples is what you will take as your measurement, and it will most likely be very close to the 'true' values, but that true value can never be known oooooo~~~~~~ What is a uni-variate distribution? A uni-variate distribution is a probability distribution of only one random variable. This is in contrast to a multivariate distribution, the probability distribution of a random vector. So the normal distribution curve that you are used to seeing is an example of a uni-variate distribution. A multivariate distribution is a generalization to higher dimensions, like how a scalar could be thought of as a special case of a vector. A normal distribution in 2-D looks something like this: What is a statistical model? A statistical model is a formalization of relationships beteen variables in the form of mathematical equations. It describes how one or more random variables are related to one or more other variables. The model is statistical as the variables are not deterministically but stochastically related. An example would be nice here. (A stochastic system is one whose subsequent state cannot be determined deterministically. Stochastic means aim. A good image to have in mind is a pattern of arrows around a target stick. Factors such as weather, and kill of the archer to name a few render this process non-deterministic. Perhaps philosophically it is deterministic.) Height and age make for a very good example. They are stochastically related; when you know a person is of age 7, this influences their chances of being 6 feet tall, non-deterministically i.e. age is not enough to say for certain that that person can not be 6 feet tall. We could (and will) formalize this relationship in a linear regression model.

[leonmanrolls-blog]

Dealing with app key in ubuntu

The problem with this is that there are probably only going to be a few times within the year when you actually need to deal with signing apks and the keystore etc, but the gap between these times is enough that I completely forget how to do it every time lol. So I'm writing this here once and for all as a reference It's this: http://stackoverflow.com/questions/4594952/android-key-hash n order to generate key hash you need to follow some easy steps. Download Openssl from: http://code.google.com/p/openssl-for-windows/downloads/list Make a openssl folder in C drive Extract Zip files into openssl folder Copy the File debug.keystore from .android folder in my case (C:\Users\SYSTEM.android) and paste into JDK bin Folder in my case (C:\Program Files\Java\jdk1.6.0_05\bin) Open command prompt and give the path of JDK Bin folder in my case (C:\Program Files\Java\jdk1.6.0_05\bin). Copy the code and hit enter keytool -exportcert -alias androiddebugkey -keystore debug.keystore > c:\openssl\bin\debug.txt Now you need to enter password, Password = android. See in openssl Bin folder you will get a file with the name of debug.txt Now either you can restart command prompt or work with existing command prompt comes to C drive and give the path of openssl Bin folder copy the following code and paste openssl sha1 -binary debug.txt > debug_sha.txt you will get debug_sha.txt in openssl bin folder

[leonmanrolls-blog]

Hash map/table

A hash table is basically an associative array, mapping keys to values. The reason it is not an associative array is that it uses a hash function to compute the index depending on the key to find the correct value. Ideally a hash function should assign each possible key to a unique bucket but this is rarely achievable in practice. So what exactly do we gain from this situation? In a well-dimensioned hash table, the average number of instructions (computational cost) for each lookup is independent of the number of elements stored in the table. That is pretty amazing. That is why you use a function for each lookup... I see.

[leonmanrolls-blog]

Finding a process that is using a port and killing it

sudo netstat -lpn | rep :8080 Then, kill [process number]

[leonmanrolls-blog]

So what exactly is maven?

Maven is for building and managing any java based project. It's primary goal is to allow a developer to comprehend the complete state of a development effort in the shortest period of time. In order to do this, it attempts to deal with five key areas. Making the build process easy. Providing a uniform build system. Maven allows a project to build using it's project object model (POM) and a set of plugins that are shared by all projects using Maven. The point of this is that once you know how one maven project builde you automatically know how all maven projects build. Apparently maven also provides quality project information, such as a documented change log, cross referenced sources, mailing lists, dependency list, unit test reports including coverage. And apparently it helps provide guidelines for best practices development. However, although it says explicitly that maven is not an extension to Ant that lets you download dependencies, that is its best use as far as I can tell at the moment.

[leonmanrolls-blog]

Notes on dealing with a WebView in Android

WebView blank screen

For Android 2.2 and earlier, if you try to access a website with insecure content, it will block the page from loading without giving any indication. Workaround below. This only works for android 2.2 but at this point it is not really worth worrying about phones older than that

engine = (WebView) findViewById(R.id.my_webview); engine.setWebViewClient(new WebViewClient() { public void onReceivedSslError (WebView view, SslErrorHandler handler, SslError error) { handler.proceed() ; } }

Prevent the loading dialog from dimming the screen

This is bad because it tends to make the screen flicker from light to dark.

progressdialog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);

Code for loading dialog

Basically detects when a page starts to load and when a page finished loading, and puts up a dialog inbetween those events.

WebView.setWebViewClient(new WebViewClient() { private int webViewPreviousState; private final int PAGE_STARTED = 0x1; private final int PAGE_REDIRECTED = 0x2; @Override public boolean shouldOverrideUrlLoading(WebView view, String urlNewString) { webViewPreviousState = PAGE_REDIRECTED; mWebView.loadUrl(urlNewString); return true; } @Override public void onPageStarted(WebView view, String url, Bitmap favicon) { super.onPageStarted(view, url, favicon); webViewPreviousState = PAGE_STARTED; if (dialog == null || !dialog.isShowing()) dialog = ProgressDialog.show(WebViewActivity.this, "", getString(R.string.loadingMessege), true, true, new OnCancelListener() { @Override public void onCancel(DialogInterface dialog) { // do something } }); } @Override public void onPageFinished(WebView view, String url) { if (webViewPreviousState == PAGE_STARTED) { dialog.dismiss(); dialog = null; }

[leonmanrolls-blog]

OOP in JavaScript

Let's start from the beginning. Everything in JavaScript is an object, apart from the primitives, the fantastic five: String, Number, Boolean, Undefined and Null. The collection of primitives plus the concept of an object make up the basic 'types' in JavaScript. Types are the building blocks of any language. The thing to be aware of is that often times when you interact with primitives JavaScript will create a wrapper object for your convenience, masking the primitive's true form (The text between the stars is the console ouput).

var something = 'baldebal'; console.log(something); ** baldebal **

Fine. So what happens when we call a method on this string?

//The steps followed by JavaScript will be as follows: //1.Convert s into a string wrapper object, //equivalent to using new String(s). var s = new String('foo'); console.log(s); ** String {0: "f", 1: "o", 2: "o"} ** //2.Call the substring method with the correct paramters. console.log(s.substring(1,2)); ** o ** //3. Dispose of the string object //4. Return the (primitive) string from step 2.

If the primitive was an object, we would be able to define some properties on it.

var s = 'baldebal'; s.prop = 'Added propery'; console.log(s.prop); ** undefined **

This doesn't work, but if we try this when we explicitly make a string object, it does work.

var s = new String('bladebla'); s.prop = 'Added property'; console.log(s.prop); ** Added Property **

So far, so good. The main point is that apart from the stuff that is better off not being an object, everything else is an object, and due to the way JavaScript behaves, thinking of everything as an object will get you to where you want to go most of the time. On to OOP. Understanding prototypes is critical to this.

Prototypes in JavaScript

AFAIK all functions in JavaScript can be thought of as constructors for an object, we just might not use that object all the time. We want to think in this way because we want to stick the idea that everything in JavaScript is an object. Even if you invoke a self-executing function, it is a constructor for an object that potentially will be used to carry out the work that the function needs to do which will not survive past the execution of the function :(. That object that is created can be referenced with the 'this' key word. In chrome, we have a very useful method, console.dir(). It gives us the JavaScript representation of whatever we pass into it. So if we want to take a look at the object associated with a function, we can type console.dir(function name) and see the output in the chrome console. We will start off with a simple function:

function parent (input){ this.firstinput = input; } console.dir(parent);

Here we can see the object associated with this function. The two things we want to focus on are the prototype and __proto__ properties. __proto__ refers to the object that parent is using as its own prototype, wheras prototype is a pointer to where anything that inherits from this function should set its prototype as, and in this case it wants child functions to point to itself. We can see this by making a new variable from this constructor function.

function parent (input){ this.firstinput = input; } var x = new parent('Father'); console.dir(x);

Interestingly according to chrome, the prototype property of our instance variable does not exist. Is this true? Well I can't use our x instance variable to do something like this:

var z = new x(); var z = new x;

It throws an error on both lines. So there won't be a case where I could use this instance variable's prototype property even if it had one. The closest thing to constructing that I could do is use this instance variable as the prototype of another instance variable by doing the following:

var z = new Object(x);

This essentially creates a clone of the original object in this example, with the console.dir() output being the same as for x. Hopefully the difference between the two prototypes is clear now, but how can we use this prototype property with regards to OOP, or more specifically inheritance? Take a deep breath...

function Animal(name) { this.name = name; } Animal.prototype.age=1; function Cat(name, color) { Animal.call(this, name); this.color = color; } Cat.prototype = new Animal(null); var catC = new Cat("Fluffy", "White"); catC.name; **Fluffy** catC.color; **White** catC.age; **1** catC.hasOwnProperty("name"); **true** catC.hasOwnProperty("color"); **true** catC.hasOwnProperty("age"); **false**

The call method allows us to use the function animal but on a different object, the one we pass to it, 'this' in this case. We then pass it any information it needs. By passing 'this' the results of running Animal truly belong to the new object we are making, as shown by catC.hasOwnproperty() below. We can get the age because we set the prototype property to be a new Animal, if we did not set this the age would be undefined. We can see that the age property is not a property of this object itself, but when JavaScript could not find that variable it went looking up the prototype chain. As we set its prototype to Animal it found it after going one step up the chain. If we had not set this, it would have gone looking in object instead and would not have found it, returning undefined.

[leonmanrolls-blog]

Sublime Text 2 vintage mode tip: end of line key binding.

In vim, one can temporarily put themselves into command mode by typing ctrl+O, and then could reach the end of the line by typing shift+A. Although tab is good for getting out of brackets and quotation marks some of the time, I find it tends to be unreliable. Perhaps I am doing something wrong? Anyway this is where I find the most use for a end of line short cut, finishing off a programming statement with a ';' when I'm still inside a bracket. Vintage mode has yet to implement this and to be honest there are more important missing features that should take priority I'm sure. So I added the following key binding to make Alt+; do the same thing:

{ "keys": ["alt+;"], "command": "move_to", "args": {"to": "eol", "extend": false} }

which is actually half the keystrokes it takes to the same thing in vim. 1-0 to Sublime Text 2!

[leonmanrolls-blog]

The annoying [object Object]

I do see this from time to time during my javascript travels, and always wonder what it is. Well, once again stackoverflow comes to the rescue. The default conversion of an object to a string is [object Object], which means that if you really want to inspect an object it is much better to print it to console and view it there.

[leonmanrolls-blog]

Sublime text 2 Vintage mode key remap.

When using vim I prefer to remap the hjkl keys to jkl;, simply because I think it is unnecessary to be forced to shift your hand around when moving in and out of insert mode. To do this, simply add the following to Preferences>key bindings-User. { "keys": [";"], "command": "set_motion", "args": { "motion": "vi_move_by_characters_in_line", "motion_args": {"forward": true, "extend": true, "visual": false }}, "context": [{"key": "setting.command_mode"}] }, { "keys": ["j"], "command": "set_motion", "args": { "motion": "vi_move_by_characters_in_line", "motion_args": {"forward": false, "extend": true }}, "context": [{"key": "setting.command_mode"}] }, { "keys": ["k"], "command": "set_motion", "args": { "motion": "move", "motion_args": {"by": "lines", "forward": true, "extend": true }, "linewise": true }, "context": [{"key": "setting.command_mode"}] }, { "keys": ["l"], "command": "set_motion", "args": { "motion": "move", "motion_args": {"by": "lines", "forward": false, "extend": true }, "linewise": true }, "context": [{"key": "setting.command_mode"}] } between the square brackets. If you have other key bindings in that file, remember to add a comma to the former last key binding. Changes made in user mode persist through updates of sublime text, whereas changes to the default key bindings do not.

[leonmanrolls-blog]

Playing with perfect numbers: Part 2.

What is the biggest integer that my computer can handle?

As the size of these perfect numbers gets pretty large pretty quickly, this question is one that really needs answering. I'm also very curious to find out the personal best of my computer. It has 16GB of physical ram was well as 28GB of swap space, so it should be able to handle numbers with digit counts heading off into the millions. I decided to generate a really big java BigInteger number and repeatedly multiply it by itself. After about 24 hours the computer had created a number 8 million digits long and had used hardly and ram. I couldn't really wait to see the biggest number it could make but it surely would run off into the billions of digits. I have decided to simply go ahead an write the algorithm to generate perfect numbers. This will be outlined in the next post.

[leonmanrolls-blog]

Playing with perfect numbers: Part 1.

.red{color:red;}

Perfect numbers are numbers that are the sum of their divisors. For example, 6 can be divided by 1, 2 and 3. If we add up 1, 2 and 3 we get 6. I decided to take a look at the first 5 perfect numbers: 6, 28, 496, 8128, and 33,553,336 to see what I could find.

6: 1, 2, 3. 28: 1, 2, 4, 7, 14. 469: 1, 2, 4, 8, 16, 31, 62, 124, 248. 8128: 1, 2, 4, 8, 16, 32, 64, 127, 254, 508, 1016, 2032, 4064. 33550336: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8191, 16382, 32764, 65528, 131056, 262112, 524224, 1048448, 2096896, 4193792, 8387584, 16775168.

Some patterns start to emerge.

There is only one odd number in the list of divisors, highlighted in red.

The divisors are double their previous entry until we hit the odd number which breaks this pattern, before immediately continuing with the doubling. This happens once in each list.

The index at which the odd number occurs is always a prime number (see below).

So if we index the divisors for each perfect number with n (n = 0, 1, 2 ,3 ...) we can list the index at which the odd number appears in each list.

Odd number indexes: 2, 3, 5, 7, 13.

They are all prime numbers! 11 is skipped. I tried this for the next three magic numbers, and their odd numbers also occurred at prime indexes 17, 19, and 31. Kind of cool. It seems like a well timed break in a simple doubling pattern is enough to produce a perfect number, with the prime numbers giving us a clue as to where that break should be. The wikipedia page does not mention these properties, which means they are most likely false, or unproven, or simply so obvious to even the most casual of observers that they are not even worth mentioning! So more explicitly, this is what we want the software to be able to do:

Accept a list of primes

Accept a list of perfect numbers

Calculate the divisors of those perfect numbers

Count the number of odd divisors of each perfect number

Note the indexes of the odd number(s) in each perfect number

Go through those indexes and check that they are all prime

So to test the observations from earlier, we want there to be one odd divisor for each perfect number, and for all the indexes to be prime. It would be nice to have a list of primes in a .txt file with each number on its own line. Luckily this website provides this for all prime numbers between the range 0 - 1,000,000. We will take the 0 - 100,000. There are relatively few known perfect numbers, only 44 of them. However the largest one has 19,616,714 digits! I'm not sure how many of them it will be feasible to test, and after a quick search online i could only find a calculator that accepts numbers up to 20 digits long. So now we have an excuse to start coding. Well, this just shows my ignorance but it becomes very very difficult to factor numbers as the number of digits goes up. As the size of the task is starting to dawn on me, this post will act as a statement of intent. It is possible this line of inquiry could end up being quite lengthy. The story will be continued in the next post. Click here to go to part 2