Geeks Portal

Hello

kusumo — Tue, 11 Jun 2013 07:02:00 GMT

padahal udah lama daftar baru nulis blog pertama

Hello Cruel World :D

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Web Programming Dengan Haskell

LonTonG — Mon, 27 May 2013 04:09:00 GMT

Setahun belakangan ini sesuatu banget buat saya dari sisi pengembangan diri. Sebagai orang yang punya latar belakang programmer imperatif (saya hanya bisa menulis kode dalam bahasa C dan sedikit di Basic), memberanikan diri untuk masuk ke dunia pemrograman fungsional benar - benar suatu pengalaman yang luar biasa (setidaknya buat saya secara pribadi).
Singkat kata bahasa yang saya pilih adalah Haskell, alasan saya pilih bahasa ini ketimbang F#, Erlang atau Clojure saya lupa :)
Mungkin yang bisa saya ingat adalah setelah 13 tahun saya fokus di C dan sedikit - sedikit lihat bahasa pemrograman lain, 1 hal menjadi jelas buat saya yaitu saya tidak tertarik kepada bagaimana syntax suatu bahasa pemrograman namun saya lebih tertarik kepada sisi matematisnya, yaitu semakin dekat (atau semakin mirip ekspresinya) suatu bahasa pemrograman dengan ilmu matematika. Dan setelah saya beli dan baca buku The Haskell Road to Logic, Maths and Programming, semakin saya yakin bahwa ini perjalanan saya selanjutnya.

Latar belakang saya di C (imperative programming) seperti mimpi buruk sewaktu saya coba baca baris kode seperti ini:
exceptOnFailure :: MonadBase IO m => m (Either String v) -> m v
exceptOnFailure = (>>=either (C.throwIO . EitherException) return)
Apa maksudnya baris kode ini? 11 12 ini dengan Perl :)
Untuk mempersingkat waktu, ritual "hair pulling & head banging" paling intens saya lakukan dalam perjalanan kali ini.

Inti kebijakan Zen berkata, orang yang berada di pinggir danau tahu tentang air namun berbeda dengan orang yang sudah berenang di danau tersebut, dan orang yang sudah berenang di danau berbeda pengetahuannya tentang air dengan orang yang sudah pernah menyelam.
Saya buat aplikasi web (WoM and community) dengan menggunakan bahasa pemrograman Haskell (tentunya), dan dengan memanfaatkan: Happstack (web framework), HDBC-sqlite3 (driver database), Hamlet (type-safe templating). Dan menyesuaikan dengan kompleksitas aplikasi yang saya bangun, segera akan saya gunakan web-routes-boomerang dan acid-state.

Secara sederhananya aplikasi yang saya bangun akan mentranslasikan setiap request header ke controller yang dituju, sebagai contoh:

myApp :: (IConnection a) => a -> ServerPart Response
myApp db = msum
    [ dir "static" $ serveDirectory DisableBrowsing [] "static"
    , dir "tpl" $ serveDirectory DisableBrowsing [] "tpl"
    , dir "thumb" $ serveDirectory DisableBrowsing [] "thumb"
    , dir "page" $ path $ \sid -> do R.method GET >> (showSites db sid)
    , dirs "category/new" $ R.method GET >> (showInsertCategoryForm)
    , dirs "category/new" $ R.method POST >> decodeBody postBodyPolicy >> withData (insertCategory db)
....

loadSitesFromDb :: (IConnection d, MonadIO m, MonadPlus m) => d -> Integer -> m [Site]
loadSitesFromDb db page = do
site <- liftIO $ handleSqlError $ quickQuery' db "SELECT A.siteID, A.siteName.."

return $ map sitesFromDB site
where sitesFromDB [sqlSiteID, sqlSiteName...] = (item)
where item = Site { siteID = fromSql sqlSiteID, siteName = ..

dengan model:

data Site = Site { siteID :: Integer
                   , siteName :: String
                   , sitePhoneNum :: String
                   , siteCategoryID :: String
                   , siteURL :: String
                   , siteRating :: String
                   , siteDescription :: String }

instance FromData Site where
fromData = do
    sID <- look "_id"
    sName <- look "_name"
    sPhoneNum <- look "_phoneNum"
    sURL <- look "_URL"
    sCategoryID <- look "_categoryID"
...

Yang akhirnya dipresentasikan dengan:

                    <ul class="thumbnails">
                        $forall site <- sites
                            <li class="span3">
                                <div class="thumbnail">
                                    <img src="/thumb/#{siteID site}t.png" alt="" class="img-polaroid" />
                                    <div class="caption">
                                        <h5>#{siteName site}
                                        <p><a href="/review/#{siteID site}" data-target="#commentModal" role="button" class="btn" data-toggle="modal">

                            $forall x <- enumFromTo 1 $ (div numrows 30)
                                $if (==) x page
                                    <li class="active"><a href="/page/#{show x}">#{show x}</a>
                                $else
                                    <li><a href="/page/#{show x}">#{show x}</a>
....

Khusus bagian V nya, untuk mempermudah pekerjaan saya, saya manfaatkan Bootstrap, PhantomJS (yang di-eksekusi melalui bash script di belakang layar).
So far so good untuk aplikasi web yang komplit dengan backend & frontend total LoC 300+ dan sangat concise.

Kesimpulan saya, perjalanan ini sangat layak diperjuangkan!
Sesuai dengan filosofi Haskell bahwa apabila suatu program bisa melewati fase kompilasi maka program tersebut akan baik - baik saja. Dan waktu yang biasanya dihabiskan untuk proses debugging, bisa saya gunakan untuk hal lainnya :)

Terakhir, seperti yang saya singgung di atas, ke depan saya akan menggunakan web-routes-boomerang.
Mungkin perlu saya hilite, web-routes-boomerang ini sangat powerful untuk menangani (terutama) urusan parsing URL.
Untuk project saya ke depan (aplikasi web saya di atas sudah nyaris rampung dan siap dioper ke marketing), saya akan membuat internet of things hub (restful web API) khususnya untuk device berbasis Arduino dan SoC seperti Raspberry pi.

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my new blog

cipto — Wed, 17 Apr 2013 03:07:00 GMT

http://ciptothe.wordpress.com/

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Just give me the source code please….

welly tambunan — Mon, 08 Apr 2013 15:23:24 GMT

Source code is really important for us. That’s why I love open source so much. Well. not only as a consumer of open source, but also a producer.

Reading people codes can give you a huge knowledge about best practice and change how you write the code. Especially if the writer is good developer.

Sometimes we need so badly to see the source code… But we can’t. This is a very painful experience. Maybe we find there’s a strange error in commercial library, or maybe we need to debug in production environment when we can’t debug with our beloved Visual Studio.

Absolutely we need that source code !

Previously I create a blog post about a decompiler. I use RedGate Reflector. But. it’s not free and my trial version has been over.

You can read the complete article here

http://weltam.wordpress.com/2013/04/08/just-give-me-the-source-code-please/

Cheers

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Grab your Visual Studio 2012 Update 2

welly tambunan — Sat, 06 Apr 2013 08:03:46 GMT

I know I’m a lil bit late joining the party for installing VS 2012 update 2. But just get my internet connection upgraded. The first thing I do to download the VS 2012 update 2.

I think I need to create an offline installer and share it to my colleague next week. Yes. You can create an offline installer. I think this is the best way to install it. You can share it with others and save a national bandwith.

Seems I’ve got a problem uploading image with LiveWriter to geeks blog. You can follow the complete article here

http://weltam.wordpress.com/2013/04/06/grab-your-visual-studio-2012-update-2/

Enjoy it !

Cheers

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LiveWriter, Visual Studio and My Code

welly tambunan — Tue, 26 Mar 2013 08:30:59 GMT

I’ve been using LiveWriter quite some time for now. It’s very easy and comfortable. Today I’ve found an interesting blogpost that explain how to paste code to LiveWriter so it can be displayed beautifully.

How to: Add a ‘Copy Code’ Link to Your Blog Post and Colored Code Blocks

This actually what I needed. My favorite IDE and Blog editor live happily ever after.

   public class HappyDayEA : EExpertAdvisor
    {
        private IOrderManager _orderManagement;
        private const double LotSize = 1;
        private Order _buyOrder = null;
        private Order _sellOrder = null;
        private DateTime prevtime = default(DateTime);

        private bool isInitialize = false;
        
        protected override int Init()
        {
            _orderManagement = new NoOrderCreatedManager(this);
            prevtime = Time[0];
            isInitialize = true;
            return (0);
        }

        internal void CreatedMagicBoxFromPreviousCandle()
        {
            _buyOrder = PendingBuy(Symbol, LotSize, High[1]

Hope this helps !

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Another IE8 and jquery validation bug

cipto — Fri, 08 Mar 2013 09:44:00 GMT

I have another unique experience with IE again.apparently so much user still using it.

this time it has to do with IE8 and jquery Validation.

the on default from asp.net MVC is jquery validation 1.8.0, which does not work on IE8.

after trying to upgrade everything to the latest:

Jquery 1.9, jquery validation 1.11

based on the CDN and then use jquery Migration so that other plugin does not work.

I finally got it working by just using my current jquery 1.8.2 with increasing jquery validation to 1.8.1

fixed other bug related to kendo autocomplete.

and then another thing is when it's HTTPS, you have to make sure all your external URL also using HTTPS (you will receive an error message such as "HTTPs compromised [URL]")

so that it works on IE

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seputar web

Kasim.Wirama — Thu, 17 Jan 2013 18:51:00 GMT

http://brockallen.com/2012/04/07/think-twice-about-using-session-state/ http://www.develop.com/training-course/asp.net-mvc-4-training http://www.cloudydeveloper.com/differences-between-asp-net-web-api-and-asp-net-mvc-routing/ http://pfelix.wordpress.com/2012/03/05/asp-net-web-api-in-memory-hosting/

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Localization in Asp.Net MVC Jquery Validation

cipto — Fri, 11 Jan 2013 06:36:47 GMT

One day I encounter this issue, A DatePicker when submit is clicked will display that FIELD IS NOT A DATE

what could be wrong? well this whole thing is related to how date is parsed, for jquery validation which is the core Unobstrusive client side validation for ASP.NET MVC, the default Date Parsing may not be supporting Format that you entered

I have set my Kendo to en-AU culture, than how to set the jquery validation to understand this date format?

the answer is jquery global and then we override the way the jquery validation works

//Include what's needed
<script src="~/Scripts/globalize.js"></script>
<script src="~/Scripts/cultures/globalize.culture.en-AU.js"></script>
<script>

$(function () {
    kendo.culture("en-AU");
    Globalize.culture('en-AU');

    $.validator.methods.date = function (value, element) {
        if (value == '' || !isNaN(Globalize.parseDate(value))) {
            return true;
        }
        return false;
    };
});


</script>

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Windows Server 2012 – First Impression

kunto — Fri, 14 Dec 2012 15:10:00 GMT

Windows Server 2012 telah dirilis ke publik sejak 26 Oktober 2012. Melalui weblog ini, saya akan mencoba untuk mengulas instalasi dan beberapa fitur baru yang tersedia pada Sistim Operasi Microsoft termutakhir ini, satu di antaranya adalah Server Manager.

Instalasi berjalan sangat lancar, mudah dan membutuhkan sedikit intervensi manual, mirip dengan Windows Serve 2008 R2 dan bahkan lebih mudah. Untuk kepentingan ini sengaja digunakan versi trial Windows Server 2012 yang dapat diunduh dari tautan berikut:

Download Windows Server 2012 Evaluation

Secara singkat instalasi berjalan seperti pada screen shots berikut:

View Full Album

Setelah selesai dengan proses instalasi, dilanjutkan dengan melakukan konfigurasi Nama Komputer (Computer Name), Zona Waktu (Time Zone), Alamat-IP (IP-Address), dan lain-lain seperti berikut ini:

View Full Album

Catatan:

Secara default .NET Framework 2.0, 3.0 dan 3.5 tidak terinstal pada Windows Server 2012. Jika tidak ada koneksi internet, instalasinya dapat dilakukan dengan cara sebagai berikut:

Copy folder sources\sxs dari media instalasi ke C:\sxs
Jalankan Command Prompt sebagai Administrator, kemudian jalankan perintah berikut ini

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:C:\sxs

Dan yang menarik di sini adalah cara menambahkan Role dan Feature menggunakan Server Manager baru dengan cascaded menu, menyebabkan berkurangnya langkah konfigurasi yang harus dilakukan:

View Full Album

Dengan menambahkan Feature Desktop Experience menyebabkan kita dapat menampilkan Computer icon di Desktop.

Selamat mencoba dan berkarya, salam IT Pro.

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async await in .NET 4.0

welly tambunan — Thu, 13 Dec 2012 08:01:20 GMT

i think you are agree that async await in c# 5 is a really cool feature. I will explain in the future blog post more detail about this. The problem now how if you want to use this feature in .NET 4.0. Let say that you can’t change the production environment to the latest .NET framework (4.5).

Firstly I have already installed Visual Studio 2012 in my machine. I try to change the target framework to .NET 4

At first I’m very happy because the async keyword is appear in my editor. But the red squiggly wipe all the happines.

You can see a cause of the problem at error window. Seems there are a missing type or assembly.

The answer to our problem is :

You can gain the simplicity and beauty of asynchronous to make your apps performance better.

Maybe you see there is no executable download in the previous link. That’s because you have to get the required library through Nuget.

Search “Microsoft.CompilerServices.AsyncTargetingPack” from nugget package manager. And install the package. That’s strange that the package is for Visual Studio 11. Well. Let’s try to give it a shoot.

After you install it the red squiggly disappear. You can dive into detail what’s contained in this package from object browser

There are a a lot of extensions method contain in AsyncCompatLibExtensions.

Then writes your codes.

Compile and run it asynchronously. If you see the IL with Diassembler you can see that our async await compiled into the same result as .NET 4.5. You should thanks the compiler baby.

Cheers

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Generic EditorTemplate Asp.net MVC

cipto — Tue, 11 Dec 2012 04:14:00 GMT

I’ve got a case to create a generic HTML Editor, which I can reuse across the page.

EditorTemplate which comes with MVC sounds the person who can do the job.

if you specify a string name after @HTML.EditorFor(Lambda,”EditorName”)

it will search on View/Shared/EditorTemplates/xxx.cshtml path

How do you make it generic? simple use lambda that refer to it self

this way it will generate the name correctly

ex in your cshtml editor template:

@model string
@Html.Kendo().EditorFor(m=>m).Tools(c => c.Styles(e => { e.Add("Calibry", "calibry"); })).StyleSheets(c => { c.Add("/Content/Site.css"); }).HtmlAttributes(new Dictionary<string, object>() { { "style", "width:100%" } })

To use it at any View page

ex:

     @Html.EditorFor(model => model.Description,"MyEditor")

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Structuring Project using Require JS on Multiple Page Environment

cipto — Tue, 11 Dec 2012 04:07:00 GMT

I understand the drive for single app these days. but in this case it’s multiple page.

I am using Asp.Net MVC,How do we possibly structure the JavaScript files related to require.js while you are on multiple pages environment?.

After playing around what I did are:

1. Structure my Javascript files into folder, I follow the default main.js as the main configuration for each package

2. use Packages, Register packages at Root Layout

_Layout.cshtml (Master page)

 <script>
        //before require is called
        //can set dependency module
        //I use this as What are required by global pages in this project context
        var require = {
            //shim: {
                       

            //},
            deps: ["jquery.easing.1.3.min", "jquery.prettyPhoto.custom.min", "froogaloop.min", "video.min", "jquery.videoController.min", "jquery.advancedSlider.min"]
        };
     
    </script>
    <script data-main="scripts/main" src="/scripts/require-jquery.js"></script>
    <script>
        //set configuration
        require.config({

            //define package, will execute main.js under respective package
            "packages": ["Facebook", "Twitter"]
        });
    </script>

3. On Client page told which package to load

View/Facebook/Index.Cshtml

4.Scripts/Facebook/main.js

require([ "knockout-2.2.0", "Facebook/FacebookViewModel","domReady!"],
function (ko, FacebookViewModel) {
    debugger;
    var viewModel = new FacebookViewModel();
    ko.applyBindings(viewModel);
    viewModel.LoadData();
});

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Cracking .NET Software

welly tambunan — Fri, 30 Nov 2012 02:14:45 GMT

Are you familiar with this picture ?

If you are not then you have to visit this cool website regulary. If you have already, congrats. then you are a cool person to. :D

This is what exactly we will do in this blog post. I always thought that to crack software is really hard at university. A couple a days ago i found that actually that’s pretty simple and i believe that you can do it also. Of course i’m not want you to be pirate. Let’s just do it for fun. :)

Don’t worry we don’t have to deep dive into assembly or machine language thing in this stuff. I will.. maybe next time, if i have a chance to do it. But today it’s only a simple start for you to get your hands dirty.

I know all this stuff because previously i want to crack my friends software because it can be run in Windows 8. I try to find out why the license mechanism is not working on my Machine.

My first try is to get a the coolest software decompiler in .NET world. Reflector. If you don’t have one, please go get it and use the trial version to get the feel how great it is. I see the license routine and found out where i can leverage the weakness of this software. Just drag the assembly to reflector and open the related method. Very simple to use. Turns out that this assembly hasn't been obsfucated first.

You definitely have to obfuscate your assembly if it’s not open source project.

Here’s another assembly that has been obfuscated. You can still see the code, but i bet it will hurt your eyes, just give up and buy the license.

I include the assembly in my project, create a simple main program in my software. I try to do reflection because some of the assembly is internal. So another best practice again is…

For a really critical and high privacy class, you should keep the access at least as possible. don’t create all class public by default. that’s just plain stupid !!! If you don’t want everyone get access to it try to make it internal.

There is a very good book that will support my statement. You can check this cool book.

After a couple of headaches i finally found a very nice reflector add ins that help me to crack that software. Have you ever heard about reflexil ? That cool tools can modify an IL (intermediate language) and save the result. That’s exactly what we’re looking for. Just go download the latest version.

Extract the file and then add to reflector.

And now you can find the interesting method and see the IL

If you are not into IL, don’t worry. You can just modify the method directly and insert the relevant code. Very simple. Just right click in instruction window and choose this one

And all you have to do is replace the whole class with yours. You have to make it compile-able. Compile and click ok. Your evil IL will be inserted.

Now you can save the modified assembly by right clicking the assembly, choose reflxil and save as…

And then replace the original assembly with this one. And you are done. Right next door to hell because of cracking other people software. :)

Use this information to protect your software only. Of course that’s depend on your heart right ?

http://sourceforge.net/projects/reflexil/?source=dlp
http://geekswithblogs.net/MarkPearl/archive/2010/09/01/crack-.net-applications-101-ndash-part-2.aspx
http://geekswithblogs.net/MarkPearl/archive/2010/08/31/crack-.net-applications-101-ndash-part-1.aspx
http://stackoverflow.com/questions/451453/how-to-get-a-static-property-with-reflection

Cheers

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Scroll PullUp to Refresh, Hybrid Apps plugin

cipto — Thu, 29 Nov 2012 10:32:07 GMT

I came across this issue when building my simple news app,

I want it to behave like other apps, Pull down to refresh , Pull Up to refresh, so that when it reach bottom, I could append more news to either local storage or Sqllite

I found that this plugin called ISCROLL is very useful and it works on the simulator

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VS2012 SP1 Offline Installer

dede — Tue, 27 Nov 2012 18:00:00 GMT

Q:Apakah ada offline installer untuk VS2012 SP1?

Seperti yang kita lihat pada microsoft visual studio download page yang hanya mempunyai web installer dan tidak memberikan link untuk ISO installer (offline).
Walaupun begitu kita masih mempunyai opsi untuk men-download package sp1 ini untuk melakukan offline installer.
Caranya:

Jalankan web installer dengan option: vsupdate_KB2707250.exe /Layout
Muncul form yang dapat di gunakan untuk mengarahkan download package-nya.

Installer kemudian akan men-download package yang di perlukan kedalam folder tadi.
Stelah selesai, maka kita akan mendapatkan package-package yang diperlukan untuk melakukan 'offline installer'

Di dalam folder package kita bisa melihat banyak package VS2012 SP1 ini.
Setelah install, kita bisa melihat di about VS2012

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New Things to Learn and Adapt

cipto — Mon, 26 Nov 2012 00:16:31 GMT

Today I’ve got an hour or so to do some research a lot of things can be adapted , revisited and Implemented in real life website application

There are lots of things to Learn and see how useful it it to enhance our development cycle

Website Based:

Prototype for OOP JavaScript,, instead of verbose prototype programming ,JavaScript 1.5
Programmable CSS? think of LESS Or SASS, now CSS support inheritance and all that logic, remove redundancy
AMD JavaScript loading? use REQUIRE.JS either dynamic or predefined JS, can set up a dependency and in which order to load. this is really important and with all other combination, will keep your code clean, can use their optimizer to merge into 1 file also.

.NET Based:
CSLA.NET

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Team Leadership Books to read

welly tambunan — Sun, 25 Nov 2012 23:41:08 GMT

No one work in isolation. Team is a very precious thing that will made your software dream comes true. Need to read those book to create and maintain a great team. Here is my bucket list reading .. when i have a free time…

Definitely need some very good time to read it !

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TypeScript : Large Scale Javascript Development made easy

welly tambunan — Sat, 24 Nov 2012 10:18:03 GMT

Beberapa tahun belakangan ini javascript sudah menjadi first class language yang tidak hanya digunakan untuk aplikasi web saja tetapi juga di sisi server. Anda dapat melihat framework sepertiNode.js, framework for single page apps, bahkan video streaming and conference jg memanfaatkan kekuatan dari javascript dan HTML 5. Jangan lupa juga bahwa microsoft menggunakan javascript sebagai salah satu language yg dapat membuat aplikasi windows store apps (windows 8). Perkembangan library javascript dengan kehadiran HTML 5 juga sangat mengesankan. Sepertinya hampir tidak ada hal yang tidak bisa dilakukan dengan javascript .

Tetapi sudah bukan rahasia lagi bahwa pembangunan aplikasi dengan memanfaatkan javascript apalagi hal tersebut memiliki skala besar sangat painful. Hal ini disebabkan lemahnya dukungan dari tools dan javascript merupakan scripting language yang memiliki nature dynamic typing. Anda dapat melihat banyak buku yang akan membahas lengkap bagaimana kita bisa membuat code base kita lebih maintanable dan hal tersebut dapat dilakukan tetapi tidak mudah. Anda dapat melihat sebagian kecil dari buku yang membahas hal tersebut.

Jika anda membaca buku diatas terutama buku yang terakhir (membahas tdd, refactoring dan pattern), anda akan merasakan bahwa sulit untuk melakukan hal tersebut dengan benar.

Anda mungkin pernah mendengar mengenai CoffeScript yang menawarkan kemudahan dan ada beberapa project serupa. Dan akhirnya microsoft pun membuat bahasanya sendiri yaitu TypeScript. Seperti beberapa project yang lain typescript akan menghasilkan javascript code. Dan creatornya adalah Anders Hejlsberg yang merupakan Architect dari c#. Wow. Sintaks yang digunakan pada TypeScript juga mirip c# dan java. You will love this one. Anda juga dapat memanfaatkan VIsual Studio sebagai IDE , melakukan debugging dsb. Static typing jadi anda akan mendapat bantuan dari compiler mengenai sintaks error dsb. Awesome right ?? Ok enough marketing speech. let’s write some code.

First Cup with TypeScript

Anda dapat menginstall typescript plugin untuk visual studio dari sini.
Setelah anda melakukan instalasi anda dapat menemukan template baru pada visual studio. Berikan nama dan create project.
Anda akan mendapati file .ts (typescript) dan .js (javascript). Secara otomatis file typescript akan dicompile menjadi javascript.
Jika anda membuka file .ts dan jika background programming anda adalah java atau c# maka hal ini sangat familar sekali bagi anda. clean and beautiful.

apakah anda bisa bayangkan bagaimana membuat code tersebut dengan javascript. Silahkan anda buka sendiri file javascriptnya. very messy and hurt your eyes. guaranteed!!
Sekarang mari kita jalankan. Pastikan dulu bahwa browser yg terpilih untuk menjalankan aplikasi ini adlah Internet Explorer, karena sebelumnya saya tidak dapat melakukan debugging dengan Chrome.
Jika anda ingin mengetes fitur debugging pada bagian ini anda dapat menset breakpoint. Saya membuatnya pada constructor.
Tekan F5 untuk menjalankannya. Anda akan mendapat pesan seperti berikut ini karena dia akan dijalakan di IIS. Tekan saja OK.

Internet explorer akan terbuka untuk menampilkan hasilnya. Voila aplikasi kita dijalankan dan aplikasi berhenti pada breakpoint. Anda juga akan mendapatkan fitur debugging yang diberikan oleh visual studio.
Tekan F5 untuk melanjutkan aplikasi lagi. Akan ditampilkan page seperti berikut ini.

Websocket dengan TypeScript

Sekarang mari kita membuat code sederhana. Saya penasaran bagaimana dengan dukungan HTML 5 pada typescript. Dan fitur yang saya cari adalah ??? the most powerful one from HTML 5. WEBSOCKET !!. Let’s do it. Saya akan menggunakan server websocket yang dapat diakes disni http://www.websocket.org/echo.html.

Anda dapat melihat alamat websocketnya adalah ws://echo.websocket.org. Hanya merupakan simple reply dari server. Anda dapat mencoba terlebih dahulu demo nya untuk memastikan dukungan websocket pada browser anda dan juga tidak ada masalah dengan firewall dan NAT.
Tambahkan code yang telah di highlight berikut ini.

Perhatikan pendeklarasian variable dengan static type, intellisense pada websocket dan penggunaan lambda expression untuk callback. Sangat indah sekali.
Langsung saja kita jalankan dengan menekan F5. Anda akan mendapat pesan bahwa koneksi websocket telah dibuat ke server.

Tekan OK dan message anda akan dibalas oleh server.

Anda dapat melihat presentasi mengenai javascript langsung dari pembuatnya dari dua video berikut ini.

Have fun with TypeScript !!!

Cheers

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An adventure journey of Functional Programming and F# 2.0 in Visual Studio 2010: Part 4 of 17

eriawan — Sun, 18 Nov 2012 20:00:28 GMT

Hello there!

After a very long “quiet time” in blogging, now it’s time to encourage myself to share again! But I’d love to blog in my only passion and I truly confident about: programming, especially programming in .NET and Java. Actually, I’ve written an eBook about F# before but it was way before Visual Studio 2010 launched. Now I’m focusing on F# and functional programming.

This blog of F# contains full (long) blog posts of adventure in functional programming and F#. I call it adventure, because I’ll try to make F# as fun to as possible to learn.

Now, here are the parts:

Part 1: Introduction to Functional Programming
Part 2: Functional Programming Concepts
Part 3: Introduction to F#
Part 4: Functions, Delegates and Computation expressions in F# (you are here)
Part 5: F# standard libraries
Part 6: OOP in F#
Part 7: Using LINQ in F# (and the upcoming F# 3.0)
Part 8: F# Asynchronous workflow
Part 9: F# MailboxProcessor
Part 10: Units of Measures
Part 11: F# Power Pack
Part 12: F# for Silverlight 4 (and above)
Part 13: A look at F# 3.0 in VS 11 (Visual Studio 2012)
Part 14: A look of Functional Programming in VB 10 and C# 4.0 compared to F#
Part 15: A look of F# compared to Haskell, Scala and Scheme
Part 16: F# future and what features that F# must have
Part 17: Retrospective

Function, Delegates and Computation Workflow in F#

Before we dive deeper into this, please remember one thing: functional programming is programming with functions, just like mathematical functions. It doesn’t matter whether we are into pure functional or non pure functional.

Pure functional or non pure programming has to be able to handle side effects, and this is why Monad concept is so popular in functional programming languages. Therefore it’s useful to know Monad concept as well.

We are now learning the what the heart of functional programming is, the function. Only now let’s dive and focus on F#’s functions.

Functions in F#

In functional programming, there are no differences between data and functions, and functions can be passed as data. We already can pass function as arguments using delegates. But functions and delegates in F# are quite different from C# and VB delegates that usually uses Func<T>, Func <T,TResult> and the other larger amounts of Func parameters.

We have learned that in previous part 2 and part 3, functions in F# are special. They can be curried and then can be chained and also composed as higher order function, not just simple function that return a value.

The function itself can be treated as data, therefore can be passed as parameter to other function.

We already have this in .NET, under the name of Delegate. Because it’s on .NET, it’s available for other languages not just F#; delegates can be immediately used in C#, VB and managed C++.

Let’s make a function that has square operation:

let square x = x * x

The signature will be:

int –> int

Because there’s no type declared, the default will be Int32.

Now, using the function is simply calling the function with parameter, like this example:

square(5)

Of course the result is 5 x 5 = 25.

In F#, a function is curried (see previous part 2) and you will be able to chain it up and to create a higher order function.

Why do you have to care about the signature? Because this is the nature of F# function: it can be curried as well just like functions in part 2. Also it’s different from VB and C# when it has been compiled!

Before diving deeper, let’s dissect common F# code in a project (instead of using interactive mode).

By default, the common function declarations of F# exists in Modules, and these modules are simply the same as static classes in C# and Modules in VB. But declaring functions in F# is different.

Here is a sample of math module:

module MathModules

let sqr x = x * x

let rec simpleFactorial x = 
    if x = 0 then 1 else x * simpleFactorial x - 1

As we see, it’s simple.

Now, let’s dive into the source code of MathModules in C#: (using free JustDecompile from Telerik)

In the source in C# we can see that it has CompilationMapping attribute attached to it, and it’s simply to define the class as Module in F#. Without any modifier means that all functions in F# are public and static by default.

Again, the source decompiled in C# is longer than the one in F#, and it has many noises.

As described in previous parts (especially part 2 and part 3) if there’s no type signature in a simple arithmetic operation, the type will be inferred as integer.

What about multiple parameters?

Then the decompiled version will be:

Again, it’s different, and there is CompilationArgumentCounts attribute at the multiply function.

What is this attribute, really? Seeing this on MSD Library:

It means that this function accepts a partial application of some of its arguments. Now, when we have multiple parameter, then it can be curried as well!

Let’s recall this currying sample from Part 2:

Now, let’s incorporate those sample into our MathModules:

Now we have a higher-order function, it is “makeFactorOf3”.

And launch a decompiler tool to sneak in C#: (I have hidden the same sqr method to increase overall source code difference)

F# compiler has converted makeFactorOf3 to be typed as FSharpFunc<int,int>!

And the F# compiler generates new internal class of makeFactorOf3u004012 with code that has invocation of multiply. This is where the similarity between F# and other languages in Visual Studio break!

And you might wonder how to call this function from other languages such as C# and VB? Later on Part 14.

Now let’s explore F# functions and delegates deeper.

Returning value of function result

By looking at simpleFactorial function, we can have function body more than one line and also can have statements. But there’s one convention: the final line on the function body or the entire expression within the function body (including the statement) must evaluate into a value, and this value is the return value (or simply the result) of the function. Therefore, there’s no verbose return statement in F#.

But we must include indentation to signify that the function is indeed having many statements inside for functions that has many statements.

This concept will imply that we must evaluate value returned in a maintainable manner, as simple as possible!

This is different from C# and Visual Basic which can have return statement at any position! But this simple convention will give us more discipline that always has one point of return value, instead of having many return statement in our code.

What about using match (pattern matching) in F#? It is still evaluate to a value to be immediately returned as function result.

See this sample:

let defineQuality grade = match grade with
                        | "A" -> "Best"
                        | "B" -> "Very good"
                        | "C" -> "Good"
                        | "D" -> "Bad"
                        | _ -> "Undefined"

Compare it to C# code with the same functionality:

        String defineQuality(String grade)
        {
            var qual = "";
            switch (grade)
            {
                case "A":
                    {
                        qual = "Best"; break;
                    }
                case "B":
                    {
                        qual = "Very good"; break;
                    }
                case "C":
                    {
                        qual = "Very good"; break;
                    }
                case "D":
                    {
                        qual = "Bad"; break;
                    }
                default:
                    {
                        qual = "undefined";
                        break;
                    }
            }
            return qual;
        }

Yes, we can enforce to make return statement in one position just like the code above.

But this will become obvious if we use if statement, just like this in C#:

        String IsPositive(int anynum)
        {
            if (anynum>=0)
            {
                return "Positive";
            }
            else
            {
                return "Negative";
            }
        }

When I was leading a team of developers, I often found that code and when the inside if bracket the code contains another ifs and returns, the code will become hard to maintain and it’s still true until now! We will have two maintenance point of return values in that code above.

Now compare the code above in F#:

let IsPositive x = if x >= 0 then "Positive"
                    else "Negative"

It’s somehow quite a little bit hard to maintain but it still doesn’t violate F# convention to return value immediately. Now we can refine the function above into:

let IsPositiveV2 x = 
                let evalResult = if x>= 0 then "Positive" else "Negative"
                evalResult

Now we can see that evalResult is acting as the return value of the result, and we must have indentations.

If you want to explicitly specify the type of the returned values, you have to group the parameter into parentheses.

For example:

let multiplyV2 (a) (b) : int = a * b

and multiplyV2 will have this signature:

val multiplyV2 : a:int -> b:int –> int

This brings another convention: the last type in a function signature means the result/return value type.

Writing parameters of a function

Now let’s dive deeper about parameters in a function in F#.

We already have “sqr x” and “multiply a b” and we can simply deduce the parameters:

In F#, we define the function prefixed with let and the parameter is separated with white space. This white space is significant, therefore the next identifier after first parameter will the second parameter.

If we have the previous swap function: (also available in F# Tutorial template in Visual Studio)

let swap (a,b) = (b,a)

F# will translate the parameter as Tuples of a and b. And it will also infer the types of a and b as generic.

Recursive functions

Any recursive functions has to be marked with rec keyword after the let keyword.

We already have a recursive factorial sample in the F# tutorial:

let rec factorial n = if n=0 then 1 else n * factorial (n-1)

Again, notice the rec keyword after let.

Function as values (alias delegates in F#)

In all functional programming languages, functions are the same as values. This function as values is the same concept as delegates in .NET. We all know that many LINQ extension methods have delegates as its parameters, and so does F#.

For example: (taken from MSDN Library)

let apply1 (transform : int -> int ) y = transform y

The type of apply1 will be: (using F# interactive)

a function that has parameters of transform function that has int –> int and a y parameter with default type inferred as int, and the body of the function has transform function that takes y as parameter.

We can use the apply1 into these:

let increment x = x + 1

let result1 = apply1 increment 100

Multiple arguments/parameters are separated by “->” sign.

For example:

let apply2 ( f: int -> int -> int) x y = f x y

let mul x y = x * y

let result2 = apply2 mul 10 20

Now we can apply mul function because it has the same signature as f, int –> int –> int.

Again, in functional programming world, the last type always means the return value type.

do Bindings

We can also execute code without function definition or simply executing it independently in F#.

The way we do this in F# by using “do” binding. We can also apply attribute to a do binding.

We can use this techniques to run a code as entry point in a Windows Forms.

A sample usage of F# do binding in a Windows Forms:

open System
open System.Windows.Forms

let form1 = new Form()
form1.Text <- "XYZ"

[<STAThread>]
do
Application.Run(form1)

Lambda Expressions

Now the fun part in F# functions: lambda expressions. The lambda expressions in F# is the same concept as lambda in C# and VB, and prefixed with keyword: “fun”. The purpose of lambda syntax is only for convenience for writing anonymous function (delegate).

A small sample of lambda:

let list = List.map (fun i -> i + 1) [1;2;3]

List.map is conceptually the same as Enumerable.Select in LINQ.

Let’s dive into this lambda deeper!

Now I will use Seq.map to project a collection to another type of collection:

open System.Diagnostics
open System.Linq

let ProcessList = Process.GetProcesses()

let ProcessNames = ProcessList |> Seq.map(fun p -> p.ProcessName)

The Seq.map works conceptually the same as Select in LINQ.

Let’s decompile it! Here’s the layout of the code:

F# compiler will create many compiler generated code. What will ProcessList and ProcessNames look like?

And now let’s dive into the generated u0024.MathModules, we’ll have this:

And the call to Seq.map is available on static constructor of u0024MathModules:

IEnumerable<string> strs = SeqModule.Map<Process, string>(processNamesu004025, (IEnumerable<Process>)processArray);

And you can deduce that any Seq operation actually mapped to SeqModule class with many static functions.
Also List is mapped to ListModule respectively.

Now, where is the content of lambda?

It’s available on ProcessNamesu004025:

Again, delegation in F# is implemented as FSharpFunc internally. And you can see its “p.ProcessName” body is in the Invoke method.

There’s another attribute to hide the other field, the DebuggerBrowsable with parameter DebuggerBrowsableState.Never on it. This also means that this class isn’t meant to be used outside.

Again, this means that F# objects and functions are available for the other programming language as well as long as you don’t have to care the generated code produced by F#.

A gentler introduction to Computation Expressions in F#

A computation workflow is one of F# unique feature comparing to C# and VB. It’s somehow can bring new constructs to your code but it also brings Monad to your everyday use of F#, in a gentler way.

According to F# definition on MSDN Library:

“Computation expressions in F# provide a convenient syntax for writing computations that can be sequenced and combined using control flow constructs and bindings. They can be used to provide a convenient syntax for monads, a functional programming feature that can be used to manage data, control, and side effects in functional programs.”

Now, we can simply assume that F# can do Monad as well! But why it is needed?

As we have discussed before in part 1 and 2, it’s common in functional programming languages to compose functions, not just using it alone or chaining it up (using the “|>” in F#).

This composition comes very handy when you want to construct a DSL or simply encapsulating side effects.

For those outside F#, we can find a sample of Monad in LINQ: the SelectMany! It composes two Func<T,U> and compose it or bind it.

The syntax is:

builder { expression }

The builder is the builder name, and the expression can contain one or more the bang statements (statements that end with !) such as let! and do! statements.

I call them statements, because F# MSDN call them just keywords but this is somehow quite confusing. These keywords need expressions, just like statements in C# and VB.

Then it’s explained further:

“In computation expressions, two forms are available for some common language constructs. You can invoke the variant constructs by using a ! (bang) suffix on certain keywords, such as let!, do!, and so on. These special forms cause certain functions defined in the builder class to replace the ordinary built-in behavior of these operations. These forms resemble the yield! form of the yield keyword that is used in sequence expressions.”

In F#, we already have computation workflow in action: async in asynchronous workflow! More async in part 8.

Here’s the list of methods available for computation expressions:

(taken from http://msdn.microsoft.com/en-us/library/dd233182.aspx )

The most common use is let! keyword. It requires a builder with Bind expression inside of it. The bind will compose two expressions as long as the type is aligned well.

This is the translation from expressions:

The bind in F# inspired by bind in Haskell, and it’s quite simplified version of Haskell’s but without type classes.

Therefore, this meet the common requirement of Monad: (as explained gently by Wes Dyer in http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx blog entry)

Left identity: Identity.Compose(f) = f
Right identity: f.Compose(Identity) =f
Associative: f.Compose(g.Compose(h)) = (f.Compose(g)).Compose(h) and it is equal to “f o g” = f(g(x))

Now we get back to SelectMany:

IEnumerable<TResult> SelectMany<TSource, TResult>( this IEnumerable<TSource> source,
Func<TSource, IEnumerable<TResult>> collectionSelector)

It is the same as bind with this signature:

Bind :: IEnumerable<'T> * ('T –> IEnumerable<'U>) –> IEnumerable<'U>

Abstract that into:

Bind :: M<'T> * ('T -> M<'U>) -> M<'U>

Done, we have monads!

Suppose we want to make Monad for UI. In this sample provided by Adam Granicz from http://www.devx.com/enterprise/Article/40481/0/page/2 we can see the builder for WPF UI:

(I have edited and corrected some type information on the bind)

Using the builder above is simple:

let win =
    WindowBuilder()
        {   let! panel =
                PanelBuilder(StackPanel())
                    {   let! btn1 = Button(Content = "Hello")
                        let! btn2 = Button(Content = "World")
                        return () }
            return () }
 
win.Show() // Pops up the window in FSI.

Run the code in the interactive mode!

I have demonstrated the computation expressions with the twist of OOP in F#. It will be detailed for part 6, OOP in F#.

Next: F# standard libraries in part 5!

Further reference

Monad in functional programming: http://en.wikipedia.org/wiki/Monad_%28functional_programming%29
Mathematical Monad: http://en.wikipedia.org/wiki/Monad_(category_theory)
Adam Granicz article of “Working with DSL and Computation Expression in F#”: http://www.devx.com/enterprise/Article/40481

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Mobile Apps Authentication

cipto — Tue, 13 Nov 2012 10:51:19 GMT

Mobile native apps, simply take another approach when related to authentication

as what the Architecting Mobile Solutions for the Enterprise saying it’s a “Log On and Forget Pattern”

you logged In once , and never touch authentication again. it’s true your phone/tablet can be lost/stolen.

best if the authorization generate an Access Token, which you can then put on your storage until user log out.

a private & secure repository,IOS have this which will sign the data with the application key, called keychain repository.

for Android you have no choice but to encrypt it first

there has to be a services exposed, as this is another client which can be fully offline.

the token could be using openID/OAuth .

we are help by the new asp.net web API, which is MVC based with all the RESTful template.

a sample for using this token based with webAPI

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Have just finish a sample test of Hybrid App

cipto — Sat, 10 Nov 2012 11:23:58 GMT

By using Telerik Graphite , we can simulate and debug our application for hybrid apps,

the results are more precise than Mist.

Telerik Graphite has it’s debugger which is almost similar to firebug,

the other advantage by using Graphite is we don’t have to install SDK for each platform,

run each simulator and debug one by one using each SDK.

using JQM as the UI,

Knockout JS for the MVVM binding,

Cordova for Native support,

Graphite to test and debug,

BitBucket for Free GIT repository,

JSFiddle/echo/jsonP to simulate ajax & data request.

Have just done testing for saving to localStorage, and SqlLite feature.

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How to do a Clean Install of Windows 8

cipto — Sat, 10 Nov 2012 08:00:19 GMT

Swayed by the upgrade price, I decided to try “windoz 8” . there I was upgrading from 7 to 8. with a lot of belief everything will get better. after installing upgrade assistant, something is not right VS 2010 is not running, after trying to fix it ,

it turns out I broke the whole system. now VS Crash, with error that is not resolved anywhere.

“great this is just what I need. In middle of crunch Time “ mumbling.

Since my Ultra book does not have DVD Writer, which is another reason why technology does not help my life easier.

I tried to use USB Stick.

after failing one time, give up, yesterday I manage to get it running

1. follow below tutorial, to create bootable USB.

http://blogs.msdn.com/b/habibh/archive/2011/09/14/how-to-create-a-bootable-usb-flash-drive-to-install-windows-8-developer-preview.aspx

2. Copy Intel Rapid Storage Tech Latest Driver to a new folder inside the USB, I use the f6flpy-x64.zip for 64 bit usage. this way windows can detect your partition if you use SATA

http://downloadcenter.intel.com/Detail_Desc.aspx?DwnldID=21730

3. Choose and follow the instruction on screen

4. After you got in to the windows,Install all updates

I’ve got problem with my hard drive before, it hang for 15 minutes than can run again, to solve this install Intel Rapid Storage from link above, this time choose the MSI one. after that install the SATA driver update from windows update. problem solved!

If you complain about where is the Start Button,

you have lots of 3rd party apps option, free/pay, that can bring it back.

I use Pokki for now

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The Next C++ Books you have to read !

welly tambunan — Thu, 08 Nov 2012 00:10:48 GMT

C++ dalam tahun terakhir ini mengalami perkembangan yang sangat pesat. Banyak buku-buku atau artikel yang sudah tidak valid lagi. Kita sebaiknya membaca buku-buku yang terbaru mengenai c++ sehingga tidak menggunakan ilmu yang sudah lawas dan ketinggalan jaman. Berikut adalah beberapa buku yang sebaiknya dibaca untuk memperbaharui kemampuan c++ anda atau mungkin anda baru mulai belajar c++. Find this book and read it

C++ Primer Plus

Buku ini merupakan pengantar yang sangat bagus untuk c++ untuk level pemula. Mudah untuk diikuti dan lengkap. Buku ini sudah mencaai edisi ke enam sehingga sudah dapat dipastikan banyak peminatnya. Buku ini sudah mencakup c++ 11.

C++ in One Hour a Day

Pembagian waktu belajar dari buku ini cukup baik. Banyak hal-hal praktis yang disampaikan dari buku tersebut. Buku ini ditulis oleh MVP c++ sehingga anda dapat melihat penjelasan practical dan good programming practices di dalamnya

C++ Primer

Telah di update untuk c++11. Membantu anda untuk mempelajari bahasa dengan cepat, menggunakannya secara modern dan cara yang efektif. Buku ini juga dipenuhi dengan best practices dan cara menggunakan core language dan standard library.

C++ Succinctly - C++ for C# Developers

Buku ini ditulis untuk membantu developer c# mempelajari modern c++. Sehingga developer c# tidak perlu belajar dari ground zero, tetapi memanfaatkan pengetahuannya sebelumnya sehingga dapat menguasai bahasa ini dengan cepat.
The C++ Programming Language

Buku ini ditulis oleh pencipta c++ dan berfungsi sebagai buku referensi lengkap dan bukan tutorial mengenai fitur bahasa. Buku ini akan segera terbit dan terupdate dengan fitur c++ 11.
The C++ Standard Library

Buku ini memberikan pemahaman yang dalam tentang setiap komponen library dan penjelasan tentang design dari library. Dilengkapi juga dengan praktik programming yang effective dan kesalahan yang sering juga best practice. Banyak sample code yang dapat anda lihat pada buku ini.
C++ AMP

Beginning Visual C++ 2012

Buku ini mencakup pembahasan detail menggunakan c++ pada Visual Studio yang terbaru yaitu 2012. Anda dapat menemukan penjelasan dari c++ 11, c++/CLI, c++/CX dan penggunaan debugger dan tools lain nya pada visual studio.
Programming Windows 8 Apps with Microsoft Visual C++

Anda dapat menggunakan skill visual c++ anda untuk membangun aplikasi modern dengan Windows 8. Buku ini akan menjelaskan secara rinci Windows Runtime dan c++/cx. Bagaimana anda dapat menggunakan native c++ pada windows store dan juga xaml untuk membuat modern ui. Buku ini akan segera terbit.

Building Windows 8 Apps with Microsoft Visual C++

Buku ini seperti biasa akan memberikan detail step by step yang dapat anda ikuti. Secara lambat tapi pasti menjelaskan konsep disertai dengan praktek yang detail. Learn by doing exercises. Buku ini akan segera terbit.

Masih ada buku baru yg belum di daftarkan ? Let me know and i will update the list. Send me email at if05041 [at] gmail [dot] com

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[INFO] A hot thread about F# and functional programming is available on Kaskus: about Monad and Type Classes

eriawan — Wed, 07 Nov 2012 07:58:56 GMT

This is a quoted thread content F# and trends in functional programming in a discussion thread model, please follow my thread (my id on Kaskus is “erilive”) on Kaskus! And it’s available in Bahasa Indonesia!

Hi guys,

If you want to know more about F# and trends in functional programming in a discussion thread model, please follow my thread (my id on Kaskus is “erilive”) on Kaskus! And it’s available in Bahasa Indonesia!

There’s a lot of discussion happens there! And I invite you to join, and I will invite you all of those are advanced or just beginner in functional programming and F#. Some topics are very interesting but quite advanced such as type classes, but there is an easy topic about why functional programming matters.

Here’s the address:

http://www.kaskus.co.id/thread/000000000000000016890387/fpara-programmer-f-dan-functional-programming-disini-yah/

And paragraphs below are samples from the thread:

Monad sample

Quote:Original Posted By erilive on http://www.kaskus.co.id/show_post/000000000000000759711105/18/

Monad yang mana gan? Maybe monad, Identity monad, Reader monad, State monad?

Kalau Reader monad di F#, sudah ada yang bahas:
http://codebetter.com/matthewpodwysocki/2010/01/07/much-ado-about-monads-reader-edition/

Dan sepertinya kalau diimplementasikan di bahasa selain F# (kecuali kalau di Haskell) sepertinya akan menjadi kurang elegan.

Monad disini bukan "Monad" di cabang matematika Category Theory.

Kalau memang banyak peminatnya, akan saya jelaskan Monad di thread ini, agan-agan :)

Notes in English: (as translated)

Which Monad? There are Maybe Monad, Identity Monad, state Monad.

Reader Monad sample in F# has been discussed in:

http://codebetter.com/matthewpodwysocki/2010/01/07/much-ado-about-monads-reader-edition/

And if it’s implemented in other language besides F# and Haskell, it’ll be less elegant.

Monad in this context is not direct equals to Monad in Category theory from Math discipline.

Quote:Original Posted By Syinn

silahkan aja kalo mau langsung bahas monad, saya nyimak dulu ...kalo ada yang kurang ngerti , akan saya tanyakan pada anda

ada baiknya bahas yang awal dulu, yakni monad state

Dan sepertinya kalau diimplementasikan di bahasa selain F# (kecuali kalau di Haskell) sepertinya akan menjadi kurang elegan.

btw, saya ingin tahu kenapa om bisa berkesimpulan yang saya bold di atas ? bisa anda jelaskan secara tehnik dan detail?

karena soal keeleganan code pemrograman kan tergantung kreatifitas programmer itu sendiri, apapun bahasa program yang dia gunakan (ini kalo menurut saya lho, om )

Note in English:

He (Syinn) wanted to know about why I told him it’s less elegant.

And here’s my answer:

This is state monad in F# and sample code to use:

module StateMonad

let (>>=) x f =
   (fun s0 ->
      let a,s = x s0
      f a s)

let returnS a = (fun s -> a, s)

type StateBuilder() =
member m.Bind(x, f) = x >>= f
member m.Return a = returnS a

let state = new StateBuilder()

let getState = (fun s -> s, s)

let setState s = (fun _ -> (),s)

let Execute m s = m s |> fst

Now, in C#: (taken from http://taumuon-jabuka.blogspot.com/2012/06/state-monad-in-c-and-f.html)

The Bind operator is implemented below:

As you shall see, it’s less elegant!

Why IO Monad is “EVIL”?

Syinn asked again! But the topic is about why IO Monad is “EVIL”:

Here’s my answer: (and apologize if it’s quite long)

There is a blog post that describe IO Monad is evil: http://kawagner.blogspot.com/2007/02/why-monads-are-evil.html

And I assume he (Syinn) quoting that blog post although he didn’t mention it.

My definite answer is: IO Monad isn’t evil. According to that post, because value evaluation when designing IO Monad became imperative, and therefore it would break referential integrity. But it’s not! Because the nature of Haskell is non strict (lazy), the timing of the execution is not so important and the reference is not broken.

A simple sample of this is when dealing with iterator of yield in C# (since VS 2005) and in VB.NET (since VB 11 in Visual Studio 2012).

Due to the fact that I/O is side effect, then declaring I/O must be explicit and has to be marked as signature to a part of the “world” that includes garbage collection.

Functional programming, especially the "pure" ones, forces us to be aware and be careful in handling side effect such as I/O, pointer, exceptions.