algebraic data types - Page 184

C# SqlBulkCopy and Data Entities

- by KP

Guys, My current project consists of 3 standard layers: data, business, and presentation. I would like to use data entities for all my data access needs. Part of the functionality of the app will that it will need to copy all data within a flat file into a database. The file is not so big so I can use SqlBulkCopy. I have found several articles regarding the usage of SqlBulkCopy class in .NET. However, all the articles are using DataTables to move data back and forth. Is there a way to use data entities along with SqlBulkCopy or will I have to use DataTables?

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Memory efficient import many data files into panda DataFrame in Python

- by richardh

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JDBC get/setObject vs. get/setSpecificType

- by Joonas Pulakka

JDBC ResultSet offers getObject, getInt, getString etc. methods, and PreparedStatement has analogous setters. Apart from type compile-time type safety, do the type specific getters/setters have any (dis)advantages, or is it OK to use getObject/setObject everywhere?

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How can be possible to use anonymous type fields without know them ?

- by Freshblood

Hello everybody It is really looks so cool to me how GridView's DataSource property gets anonymous type and shows results in Grid . Simply Grid.DataSource = from order in db.OrdersSet select new { order.PersonSet.Name,order.PersonSet.SurName}; How this mechanism work? how can i do something like this ?

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Providing dynamic data to webpage

- by Marius

Hi, I have a web page that displays dynamic data which changes every 2 seconds. Data is selected from various data sources including Oracle. Currently, the page reloads every 10 seconds and runs a PHP script which retrieves the data and displays the page. I have other pages that gives a different view on the same data. This means the same query is run again for them as well. If I have 4 of these pages with 10 concurrent users each, suddenly the data retrieval happens 40 times every 10 seconds, obviously not ideal. I have some ideas on how to improve this situation, but I thought I would ask from some ideas from other experts that might have come across a similar situation. I'm not bound to PHP, and my server is on a Linux platform. Regards Marius

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Providing dynamic data to webpage

- by Marius

Hi, I have a web page that displays dynamic data which changes every 2 seconds. Data is selected from various data sources including Oracle. Currently, the page reloads every 10 seconds and runs a PHP script which retrieves the data and displays the page. I have other pages that gives a different view on the same data. This means the same query is run again for them as well. If I have 4 of these pages with 10 concurrent users each, suddenly the data retrieval happens 40 times every 10 seconds, obviously not ideal. I have some ideas on how to improve this situation, but I thought I would ask from some ideas from other experts that might have come across a similar situation. I'm not bound to PHP, and my server is on a Linux platform. Regards Marius

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pointer reference type

- by Codenotguru

I am trying to write a function that takes a pointer argument, modifies what the pointer points to, and then returns the destination of the pointer as a reference. I am gettin the following error: cannot convert int***' toint*' in return| Code: #include <iostream> using namespace std; int* increment(int** i) { i++; return &i;} int main() { int a=24; int *p=&a; int *p2; p2=increment(&p); cout<<p2; } Thanks for helping!

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How to use json object notation to retrieve dbpedia json data

- by Margi

In my php code, I am retrieving json data as below. <?php $url = "http://dbpedia.org/data/Los_Angeles.json"; $data = file_get_contents($url); echo $data; ?> The javascript code consumes this json data returned from php and gets the json object as below. var doc = eval('(' + request.responseText + ')'); How to retrieve the following json data using dot notations. The keys contain URLs. "http://dbpedia.org/ontology/populationTotal" : [ { "type" : "literal", "value" : 3792621 , "datatype" : "http://www.w3.org/2001/XMLSchema#integer" } ] , "http://dbpedia.org/ontology/PopulatedPlace/areaTotal" : [ { "type" : "literal", "value" : "1301.9688931491348" , "datatype" : "http://dbpedia.org/datatype/squareKilometre" }

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Write data to an xml file.

- by Bobby

My aim is to write an XML file with few tags whose values are the regional language. I'm using Python to do this and using IDLE(Pythong GUI) for programming. While I try to write the words in an xmls file it gives the following error. UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-4: ordinal not in range(128) For now, I'm not using any xml writer library instead I'm opening a file "test.xml" and writing the data into it. This error is encountered by the line: f.write("\t\" + data + "\"). If I replace the above write statement with print statement then it prints the data properly on Python Shell. I'm reading the data from an excel file which is not in the UTF8,16, or 32 encoding formats. Its in some other format. cp1252 is reading the data properly. Any help in getting this data writtent oan xml would be highly appreciated. Thanks in advance. Bob

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Is it good or bad practice to use var everywhere? [closed]

- by Earlz

Possible Duplicate: Use of var keyword in C# Hello, I've recently been discovering the awesomeness that is the var keyword in C#. Well, I didn't think about it before but I just wrote lines of code that are along the lines of var con=CreateNewConnection(); Where this would usually be IdbConnection con=CreateNewConnection(); Is this a good use of var? Is it possible to use var too often? Are there any downsides to using it? Also, one more point of consideration: We are not worried about backwards compatability. We just care that it runs on .NET 3.5

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PostgreSQL - can't save items - "type integer but expression is of type character"

- by user984621

I am getting still over and over again this error, the column age has the type integer, I am saving into this column integer-value, I also tried to don't save nothing into this column, but still getting this error... Could anyone help me, how to fix that? PG::Error: ERROR: column "age" is of type integer but expression is of type character varying at character 102 HINT: You will need to rewrite or cast the expression. : INSERT INTO "user_details" ("created_at", "age", "updated_at", "user_id") VALUES ($1, $2, $3, $4) RETURNING "id"

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Create an anonymous type object from an arbitrary text file

- by Robert Harvey

I need a sensible way to draw arbitrary text files into a C# program, and produce an arbitrary anonymous type object, or perhaps a composite dictionary of some sort. I have a representative text file that looks like this: adapter 1: LPe11002 Factory IEEE: 10000000 C97A83FC Non-Volatile WWPN: 10000000 C93D6A8A , WWNN: 20000000 C93D6A8A adapter 2: LPe11002 Factory IEEE: 10000000 C97A83FD Non-Volatile WWPN: 10000000 C93D6A8B , WWNN: 20000000 C93D6A8B Is there a way to get this information into an anonymous type object or some similar structure? The final anonymous type might look something like this, if it were composed in C# by hand: new { adapter1 = new { FactoryIEEE = "10000000 C97A83FC", Non-VolatileWWPN = "10000000 C93D6A8A", WWNN = "20000000 C93D6A8A" } adapter2 = new { FactoryIEEE = "10000000 C97A83FD", Non-VolatileWWPN = "10000000 C93D6A8B", WWNN = "20000000 C93D6A8B" } } Note that, as the text file's content is arbitrary (i.e. the keys could be anything), a specialized solution (e.g. that looks for names like "FactoryIEEE") won't work. However, the structure of the file will always be the same (i.e. indentation for groups, colons and commas as delimiters, etc). Or maybe I'm going about this the wrong way, and you have a better idea?

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Scala: working around the "illegal cyclic reference"

- by Paul Milovanov

Hi all, I'm trying to implement a HashMap-based tree that'd support O(1) subtree lookup for a given root key. To that goal, I'm trying to do the following: scala> type Q = HashMap[Char, Q] <console>:6: error: illegal cyclic reference involving type Q type Q = HashMap[Char, Q] ^ So the question is, is there a way for me to do something of the sort without resorting to the ugly HashMap[Char, Any] with subsequent casting of values to HashMap[Char, Any]? Now, I also see that I can use something like the following to avoid the cyclic-reference error, and it might even be cleaner -- but it'd be nice to find out how to correctly do it the first way, just for the educational value. import collections.mutable.HashMap class LTree { val children = new HashMap[Char, LTree] } Thanks a bunch.

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ZeroC Ice "checked casts" in Scala

- by Alexey Romanov

ZeroC Ice for Java translates every Slice interface Simple into (among other things) a proxy interface SimplePrx and a proxy SimplePrxHelper. If I have an ObjectPrx (the base interface for all proxies), I can check whether it actually has interface Simple by using a static method on SimplePrxHelper: val obj : Ice.ObjectPrx = ...; // Get a proxy from somewhere... val simple : SimplePrx = SimplePrxHelper.checkedCast(obj); if (simple != null) // Object supports the Simple interface... else // Object is not of type Simple... I wanted to write a method castTo so that I could replace the second line with val simple = castTo[SimplePrx](obj) or val simple = castTo[SimplePrxHelper](obj) So far as I can see, Scala's type system is not expressive enough to allow me to define castTo. Is this correct?

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Interop.Outlook.UserProperties.Add causing problem during connection time

- by Akie

Hi All, I have created a plug-in for outlook. Plug-in has only below code. private void OnNewOutlookInspector(Outlook.Inspector OutlookInsptr) { Outlook.MailItem MlItem = (Outlook.MailItem)OutlookInsptr.CurrentItem; //if I remove below line. Everything is working fine. MlItem.UserProperties.Add("INSPINIT", Outlook.OlUserPropertyType.olText , true , true ).Value = "1"; } public void OnConnection(object application, Extensibility.ext_ConnectMode connectMode, object addInInst, ref System.Array custom) { applicationObject = application; addInInstance = addInInst; MessageBox.Show("in connection new 2"); OutlkApp = (Outlook.Application)application; OutlkInsptrs = OutlkApp.Inspectors; OutlkInsptrs.NewInspector += new Outlook.InspectorsEvents_NewInspectorEventHandler(OnNewOutlookInspector); } Problem I am facing is, When I send HTML mail while plug-in is enabled, receiving end it is being received as a plain text. Below is the mail content along with the header and body at recieving end. x-sender: [email protected] x-receiver: [email protected] Received: from blr-s-07.pointcrossblr.com ([192.168.1.107]) by blr-ws-134.pointcrossblr.com with Microsoft SMTPSVC(6.0.2600.5949); Wed, 22 Dec 2010 17:11:02 +0530 Received: from blrws134 ([192.168.1.175]) by blr-s-07.pointcrossblr.com with Microsoft SMTPSVC(6.0.3790.4675); Wed, 22 Dec 2010 17:11:02 +0530 From: "Ashif Nataliya" <[email protected]> To: <[email protected]> Cc: <[email protected]> Subject: RTF FRM blr to pc.com cc blr-ws-134 Date: Wed, 22 Dec 2010 17:11:02 +0530 Message-ID: <[email protected]> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_NextPart_000_00F7_01CBA1FB.36115580" X-Mailer: Microsoft Outlook 14.0 Content-Language: en-us X-MS-TNEF-Correlator: 00000000DCB2344DE8F50F4FBC91085BB5C06D55A4172000 thread-index: AcuhzRuTOBkvHPUnS1aLi9+cHNAWhA== Return-Path: [email protected] X-OriginalArrivalTime: 22 Dec 2010 11:41:02.0822 (UTC) FILETIME=[1C788860:01CBA1CD] This is a multipart message in MIME format. ------=_NextPart_000_00F7_01CBA1FB.36115580 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit HTML Test Test Mail ------=_NextPart_000_00F7_01CBA1FB.36115580 Content-Type: application/ms-tnef; name="winmail.dat" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="winmail.dat" // and some other code..... Any help is appreciated. Thanks.

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Is there any reasonable use of a function returning an anonymous struct?

- by Akanksh

Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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Common practice for higher-order-polymorphism in scala

- by raichoo

Hi, I'm trying to grasp higher-order-polymophism in scala by implementing a very basic interface that describes a monad but I come across a problem that I don't really understand. I implemented the same with C++ and the code looks like this: #include <iostream> template <typename T> class Value { private: T value; public: Value(const T& t) { this->value = t; } T get() { return this->value; } }; template < template <typename> class Container > class Monad { public: template <typename A> Container<A> pure(const A& a); }; template <template <typename> class Container> template <typename A> Container<A> Monad<Container>::pure(const A& a) { return Container<A>(a); } int main() { Monad<Value> m; std::cout << m.pure(1).get() << std::endl; return 0; } When trying to do the same with scala I fail: class Value[T](val value: T) class Monad[Container[T]] { def pure[A](a: A): Container[A] = Container[A](a) } object Main { def main(args: Array[String]): Unit = { val m = new Monad[Value] m.pure(1) } } The compiler complains about: [raichoo@lain:Scala]:434> scalac highorder.scala highorder.scala:5: error: not found: value Container Container[A](a) ^ one error found What am I doing wrong here? There seems to be a fundamental concept I don't seem to understand about scala typeconstructors. Regards, raichoo

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C# Get Type of IEnumerable<TModel>

- by Jimbo

I have a method to which I pass an IEnumerable<TModel>. Then depending on the type of TModel, the method carries out a set of instructions as below: public void MyMethod<TModel>(IEnumerable<TModel> items) where TModel : class { int operationType; switch (typeof(TModel)) { case typeof(MyModelOne): operationType = 1; break; case typeof(MyModelTwo): operationType = 2; break; case typeof(MyModelThree): operationType = 3; break; default: throw new Exception("The collection model passed to MyMethod is not recognized"); } ... } This doesnt work, I get the error: There is no application variable or memeber 'TModel'

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ItemFileWriteStore: how to change the data?

- by jeff porter

Hi, I'd like to change the data in my dojo.data.ItemFileWriteStore. Currently I have... var rawdataCacheItems = [{'cachereq':'14:52:03','name':'Test1','cacheID':'3','ver':'7'}]; var cacheInfo = new dojo.data.ItemFileWriteStore({ data: { identifier: 'cacheID', label: 'cacheID', items: rawdataCacheItems } }); I'd like to make a XHR request to get a new JSON string of the data to render. What I can't work out is how to change the data in the "items" held by ItemFileWriteStore. Can anyone point me in the correct direction? Thanks Jeff Porter

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in C# sharp, how you pronounce 'T?'

- by plinth

How do you pronounce 'bool?', 'int?' and their ilk? I've been mulling over options like "nullable of T", "T hook", "T huh", "T what" and "T" with a rising inflection. I'm not particularly satisfied with these as they seem either cumbersome or affected or both.

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Scala wont pattern match with java.lang.String and Case Class

- by Stefan

Hello fellow Scala Programmers I have been working with Scala for some month now, however I have a problem with some properly basic stuff, I am hoping you will help my out with it. case class PersonClass(name: String, age: Int) object CaseTester { def main(args:Array[String]) { val string = "hej" string match { case e:String => println(string) case PersonClass => println(string) } } } When I am doing like this I get error: pattern type is incompatible with expected type; found : object PersonClass required: java.lang.String case PersonClass = println(string) And if I then change the second line in the pattern matching to the following: case e:PersonClass => println(string) I then get the error: error: scrutinee is incompatible with pattern type; found : PersonClass required: java.lang.String case e:PersonClass = println(string) However if I change the string definition to the following it compiles fine in both cases. val string:AnyRef = "hej"

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mEncrypt/Decrypt binary mp3 with mcrypt, missing mimetype

- by Jeremy Dicaire

I have a script that read a mp3 file and encrypt it, I want to be able to decrypt this file and convert it to base64 so it can play in html5. Key 1 will be stored on the page and static, key2 will be unique for each file, for testing I used: $key1 = md5(time()); $key2 = md5($key1.time()); Here is my encode php code : //Get file content $file = file_get_contents('test.mp3'); //Encrypt file $Encrypt = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key1, $file, MCRYPT_MODE_CBC, $key2); $Encrypt = trim(base64_encode($Encrypt)); //Create new file $fileE = "test.mp3e"; $fileE = fopen($file64, 'w') or die("can't open file"); //Put crypted content fwrite($fileE, $Encrypt); //Close file fclose($fileE); Here is the code that doesnt work (decoded file is same size, but no mimetype): //Get file content $fileE = file_get_contents('test.mp3e'); //Decode $fileDecoded = base64_decode($fileE); //Decrypt file $Decrypt = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key1, $fileDecoded, MCRYPT_MODE_CBC, $key2); $Decrypt = trim($Decrypt); //Create new file $file = "test.mp3"; $file = fopen($file, 'w') or die("can't open file"); //Put crypted content fwrite($file, $Decrypt); //Close file fclose($file);

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Xsl mime type problem

- by savruk

Hi, I have a busybox with lighttpd running on as http server. My problem is while firefox and opera can get the page with applied xsl, Arora(webkit) can not. Here is the script I use to get it work: <html> <head> <script> function loadXMLDoc(dname) { if (window.XMLHttpRequest) { xhttp=new XMLHttpRequest(); } else { xhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xhttp.open("GET",dname,false); xhttp.send(""); return xhttp.responseXML; } function querySt(ji) { hu = window.location.search.substring(1); gy = hu.split("&"); for (i=0;i<gy.length;i++) { ft = gy[i].split("="); if (ft[0] == ji) { return ft[1]; } } } function displayResult() { xml=loadXMLDoc("sample.xml"); alert(xml)//Gives [object Document] $scan=querySt("scan"); $sub = querySt("sub"); xsl=loadXMLDoc("sample.xsl"); alert(xsl)//Gives Null // code for IE if (window.ActiveXObject) { ex=xml.transformNode(xsl); document.getElementById("example").innerHTML=ex; } // code for Mozilla, Firefox, Opera, etc. else if (document.implementation && document.implementation.createDocument) { xsltProcessor=new XSLTProcessor(); xsltProcessor.importStylesheet(xsl); xsltProcessor.setParameter(null,"scan",$scan) if($sub != ""){ xsltProcessor.setParameter(null,"sub",$sub) } resultDocument = xsltProcessor.transformToFragment(xml,document); document.getElementById("example").appendChild(resultDocument); } } </script> </head> <body onload="displayResult()"> <div id="example" ></div> </body> </html> I tried to see if it load xsl well and put an alert(xsl) but it gives null. Other browser can get xml and xsl files perfectly. What can be the problem? Thanks P.S: It runs well on my local server with all browser.

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Strange Scala error.

- by Lukasz Lew

I tried to create abstract turn based Game and abstract AI: abstract class AGame { type Player type Move // Player inside def actPlayer : Player def moves (player : Player) : Iterator[Move] def play (move : Move) def undo () def isFinished : Boolean def result (player : Player) : Double } abstract class Ai[Game <: AGame] { def genMove (player : Game#Player) : Game#Move } class DummyGame extends AGame { type Player = Unit type Move = Unit def moves (player : Player) = new Iterator[Move] { def hasNext = false def next = throw new Exception ("asd") } def actPlayer = () def play (move : Move) { } def undo () { } def isFinished = true def result (player : Player) = 0 } class DummyAi[Game <: AGame] (game : Game) extends Ai[Game] { override def genMove (player : Game#Player) : Game#Move = { game.moves (player).next } } I thought that I have to use this strange type accessors like Game#Player. I get very puzzling error. I would like to understand it: [error] /home/lew/Devel/CGSearch/src/main/scala/Main.scala:41: type mismatch; [error] found : Game#Player [error] required: DummyAi.this.game.Player [error] game.moves (player).next [error] ^

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Convert text file to dictionary or anonymous type object

- by Robert Harvey

I have a text file that looks like this: adapter 1: LPe11002 Factory IEEE: 10000000 C97A83FC Non-Volatile WWPN: 10000000 C93D6A8A , WWNN: 20000000 C93D6A8A adapter 2: LPe11002 Factory IEEE: 10000000 C97A83FD Non-Volatile WWPN: 10000000 C93D6A8B , WWNN: 20000000 C93D6A8B Is there a way to get this information into an anonymous type or dictionary object? The final anonymous type might look something like this, if it were composed in C# by hand: new { adapter1 = new { FactoryIEEE = "10000000 C97A83FC", Non-VolatileWWPN = "10000000 C93D6A8A", WWNN = "20000000 C93D6A8A" } adapter2 = new { FactoryIEEE = "10000000 C97A83FD", Non-VolatileWWPN = "10000000 C93D6A8B", WWNN = "20000000 C93D6A8B" } }

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- by KP

- by richardh

- by Joonas Pulakka

- by Freshblood

- by Marius

- by Marius

- by Codenotguru

- by Margi

- by Bobby

- by Earlz

- by user984621

- by Robert Harvey

- by Paul Milovanov

- by Alexey Romanov

- by Akie

- by Akanksh

- by raichoo

- by Jimbo

- by jeff porter

- by plinth

- by Stefan

- by Jeremy Dicaire

- by savruk

- by Lukasz Lew

- by Robert Harvey

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