JAVA OMG

• Name: lets call this anti-pattern signification
• Description: we can be sure that the original string will be converted to string
• Why: to much free RAM and CPU
• Example:

  new String(Integer.toString(deviceInfo.imageWidth))
  

Quine

A quine is a program that prints itself:

Quine in JS

// browser
!function $(){console.log('!'+$+'()')}()

// node
(function quine() {
    console.log(quine.toString())
})()

Quine in Java

  // http://c2.com/cgi/wiki?QuineProgram
  public class Quine {
 public static void main(String[] args) {
 String[] str = {
  "public class Quine {",
  " public static void main(String[] args) {",
  "  String[] str = {",
  "  };",
  "  for(int i=0;i<3;i++)System.out.println(str[i]);",
  "  for(int i=0;i<9;i++)System.out.println((char)34+str[i]+(char)34+',');",
  "  for(int i=3;i<9;i++)System.out.println(str[i]);",
  " }",
  "}",
 };
 for(int i=0;i<3;i++)System.out.println(str[i]);
 for(int i=0;i<9;i++)System.out.println((char)34+str[i]+(char)34+',');
 for(int i=3;i<9;i++)System.out.println(str[i]);
 }
  }

Practical use

I used quines to print my programs as slides during Functional Programming workshop.

Cat implementation of Maybe Monad

var _ = require('lodash');
var expect = require('chai').expect;

// implementation by Brandon Weaver
var maybe = function (object, methodCalls) {
    if (_.isUndefined(object)) {
        return undefined;
    }
    if (_.isEmpty(methodCalls)) {
        return object;
    }

    return _.reduce(methodCalls.split('.'), function (obj, method) {
        return obj ? obj[method] : undefined;
    }, object);
};

_.mixin({maybe:maybe});

describe('maybe', function () {

    afterEach(function (done) {
        setTimeout(done, 60);
    });

    // now
    var foodChain = [
        {food: 'mice', race: 'cat'},
        {food: null, race: 'mice'}
    ];

    var getFood = function (anml) {
        return anml.race + ' loves to eat ' + anml.food;
    };

    // with maybe
    var safeGet = function (anml) {
        return _.maybe(anml.race) + ' loves to eat ' + _.maybe(anml.food);
    };

    var betterSafeGet = _.maybe(getFood);

    it ('allows safe filters', function (done){
        // old way to do it
        var safeFilter = _(foodChain)
            .filter(function (el) {
                return el.food && el.race ? true : false;
            })
            .map(getFood);
        var mapWithBetterSafeGet = _(foodChain).map(betterSafeGet);
        var filterSafeGet = _(foodChain).filter(betterSafeGet);

        //ERROR
        expect(filterSafeGet.value()).eql(safeFilter.value());

        done();
    });

    it('gets same output as getter with if', function (done){
        var mapWithIf= _(foodChain)
            .map(function (anml) {
                if (anml.food && anml.race) {
                    return getFood(anml)
                }
            });

        var mapWithBetterSafeGet = _(foodChain).map(betterSafeGet);

        //ERROR
        expect(mapWithIf.value()).eql(mapWithBetterSafeGet.value());

        done();
    });

    it('allows safe getters getter', function (done) {
        var outSafeGet = _(foodChain).filter(safeGet);
        var filterWithBetterSafeGet = _(foodChain).filter(betterSafeGet);
        expect(outSafeGet.value()).eql(filterWithBetterSafeGet.value());

        done();
    });

    //describe dot notation
    it('is idempotent', function (done) {
        var object = {a: {b: {c: 1}}};
        expect(_.maybe(object, 'a.b.c')).eql(1); // returns 1
        expect(_.maybe(object, 'a.b.c.d.e.f.g')).to.be.undefined;
        // 1*1 ?= 1
        var one = _.maybe(_.maybe(object, 'a.b.c'), 'a.b.c');

        // ERROR returns undefined
        expect(one).eql(1);

        done();
    })
});

CPU access in NOT like File Access

Yesterday on a meeting, someone mentioned, that CPU is like File access, that if we have ex: 4 threads system. Having 2 processes accessing the all 4 threads would be on first-come-first-serve basis.
That first process will utilize almost 100% CPU power (will be resource hog). Resulting huge overhead.

That is not the case.

Modern CPU's are very efficient in switching between threads.
The CPU time (computation time) of both processes would be divided almost equally.
The computation time of each processes would be ca. twice slower. Than running them separetly.
The total computation time of both processes would be (almost) equal to time of running them sequentially.

So CPU access in nothing like File Access

BTW: Modern kernels also can give multiple file descriptors so even File access would not be on first come-first-serve-basis

It all would be ok, I mean, all people can have false assumptions, but the person stating such bologna is Head of IT Unit :(...


Further reading:
http://en.wikipedia.org/wiki/Hyper-threading
http://en.wikipedia.org/wiki/Thread_%28computing%29
 

brack.ch never again

brack.ch never again... they just sold me used phone as a new one. I start the phone.. and what do I see? A naked picture of previous owner :D ... together with his Hotmail account, and a friends list... :( What is more disturbing that the shop representative did not care at all. Apparently I'm supposed to send the phone on my cost to some 3rd party shop, and they will allow me to buy other things on theirs website up to phone cost.