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  • What should the name of this class be?

    - by Tim Murphy
    Naming classes is sometimes hard. What do you think name of the class should be? I originally created the class to use as a cache but can see its may have other uses. Example code to use the class. Dim cache = New NamePendingDictionary(Of String, Sample) Dim value = cache("a", Function() New Sample()) And here is the class that needs a name. ''' <summary> ''' Enhancement of <see cref="System.Collections.Generic.Dictionary"/>. See the Item property ''' for more details. ''' </summary> ''' <typeparam name="TKey">The type of the keys in the dictionary.</typeparam> ''' <typeparam name="TValue">The type of the values in the dictionary.</typeparam> Public Class NamePendingDictionary(Of TKey, TValue) Inherits Dictionary(Of TKey, TValue) Delegate Function DefaultValue() As TValue ''' <summary> ''' Gets or sets the value associated with the specified key. If the specified key does not exist ''' then <paramref name="createDefaultValue"/> is invoked and added to the dictionary. The created ''' value is then returned. ''' </summary> ''' <param name="key">The key of the value to get.</param> ''' <param name="createDefaultValue"> ''' The delegate to invoke if <paramref name="key"/> does not exist in the dictionary. ''' </param> ''' <exception cref="T:System.ArgumentNullException"><paramref name="key" /> is null.</exception> Default Public Overloads ReadOnly Property Item(ByVal key As TKey, ByVal createDefaultValue As DefaultValue) As TValue Get Dim value As TValue If createDefaultValue Is Nothing Then Throw New ArgumentNullException("createValue") End If If Not Me.TryGetValue(key, value) Then value = createDefaultValue.Invoke() Me.Add(key, value) End If Return value End Get End Property End Class

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  • C# generics when T could be an array

    - by bufferz
    I am writing a C# wrapper for a 3rd party library that reads both single values and arrays from a hardware device, but always returns an object[] array even for one value. This requires repeated calls to object[0] when I'd like the end user to be able to use generics to receive either an array or single value. I want to use generics so the callee can use the wrapper in the following ways: MyWrapper<float> mw = new MyWrapper<float>( ... ); float value = mw.Value; //should return float; MyWrapper<float[]> mw = new MyWrapper<float[]>( ... ); float[] values = mw.Value; //should return float[]; In MyWrapper I have the Value property currently as the following: public T Value { get { if(_wrappedObject.Values.Length > 1) return (T)_wrappedObject.Value; //T could be float[]. this doesn't compile. else return (T)_wrappedObject.Values[0]; //T could be float. this compiles. } } I get a compile error in the first case: Cannot convert type 'object[]' to 'T' If I change MyWrapper.Value to T[] I receive: Cannot convert type 'object[]' to 'T[]' Any ideas of how to achieve my goal? Thanks!

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  • How do I loop through elements inside a div?

    - by crosenblum
    I have to make a custom function for search/replace text, because firefox counts text nodes differently than IE, Google Chrome, etc.. I am trying to use this code, that I saw at Firefox WhiteSpace Issue since in my other function, I am looping numerically through nodes, which serves my functional needs perfectly, in other browsers. But refuses to work, as part of a search/replace function that takes place after some ajax content is loaded. Here is the code, that I have tried to get to work, but I must be missing the correct understanding of the context of how to loop thru elements inside a div. // get all childnodes inside div function div_translate(divid) { // list child nodes of parent if (divid != null) { // var children = parent.childNodes, child; var parentNode = divid; // start loop thru child nodes for(var node=parentNode.firstChild;node!=null;node=node.nextSibling){ // begin check nodeType if(node.nodeType == 1){ // get value of this node var value = content(node); // get class of this node var myclass = node.attr('class'); console.log(myclass); // begin check if value undefined if (typeof(value) != 'undefined' && value != null) { console.log(value); // it is a text node. do magic. for (var x = en_count; x > 0; x--) { // get current english phrase var from = en_lang[x]; // get current other language phrase var to = other_lang[x]; if (value.match(from)) { content(node, value.replace(from, to)); } } } // end check if value undefined } // end check nodeType } // end loop thru child nodes } }

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  • Create static instances of a class inside said class in Python

    - by Samir Talwar
    Apologies if I've got the terminology wrong here—I can't think what this particular idiom would be called. I've been trying to create a Python 3 class that statically declares instances of itself inside itself—sort of like an enum would work. Here's a simplified version of the code I wrote: class Test: A = Test("A") B = Test("B") def __init__(self, value): self.value = value def __str__(self): return "Test: " + self.value print(str(Test.A)) print(str(Test.B)) Writing this, I got an exception on line 2 (A = Test("A")). I assume line 3 would also error if it had made it that far. Using __class__ instead of Test gives the same error. File "<stdin>", line 1, in <module> File "<stdin>", line 2, in Test NameError: name 'Test' is not defined Is there any way to refer to the current class in a static context in Python? I could declare these particular variables outside the class or in a separate class, but for clarity's sake, I'd rather not if I can help it. To better demonstrate what I'm trying to do, here's the same example in Java: public class Test { private static final Test A = new Test("A"); private static final Test B = new Test("B"); private final String value; public Test(String value) { this.value = value; } public String toString() { return "Test: " + value; } public static void main(String[] args) { System.out.println(A); System.out.println(B); } } This works as you would expect: it prints: Test: A Test: B How can I do the same thing in Python?

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  • Speed up an Excel Macro?

    - by N. Lucas
    Right now I have a macro PopulateYearlyValues But it seems to me it's taking way too long Sub PopulateYearlyValues(ByVal Month As Range) Dim c As Double Dim s As Double c = Application.WorksheetFunction.Match(UCase(Month.Value), ActiveSheet.Range("AA5:AX5"), 0) s = (ActiveSheet.Range("AA5").Column - 1) With ActiveSheet Dim i As Integer Dim j As Integer For i = 7 To 44 .Range("G" & i).Value = 0 .Range("H" & i).Value = 0 For j = 1 To c .Range("G" & i).Value = (.Range("G" & i).Value + .Cells(i, s).Offset(0, j)) .Range("H" & i).Value = (.Range("H" & i).Value + .Cells(i, s).Offset(0, (j + 1))) j = j + 1 Next j Next i End With End Sub I have a range G7:H44 that needs to be populated with the SUM of range AA7:AX44 but.. it's only every other column: If Month.Value = "January" G7 = SUM(AA7) H7 = SUM(AB7) ... G44 = SUM(AA44) H44 = SUM(AB44) End If If Month.Value = "April" G7 = SUM(AA7, AC7, AE7, AG7) H7 = SUM(AB7, AD7, AF7, AH7) ... G44 = SUM(AA44, AC44, AE44, AG44) H44 = SUM(AB44, AD44, AF44, AH44) End If But the macro I have is taking way too long.. Is there any other way to do this?

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  • Insert or Update using Oracle and PL/SQL

    - by Shane
    I have a PL/SQL function that performs an update/insert on an Oracle database that maintains a target total and returns the difference between the existing value and the new value. Here is the code I have so far: FUNCTION calcTargetTotal(accountId varchar2, newTotal numeric ) RETURN number is oldTotal numeric(20,6); difference numeric(20,6); begin difference := 0; begin select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; exception when NO_DATA_FOUND then begin difference := newTotal; insert into target_total ( account_id, value ) values ( accountId, newTotal ); -- sometimes a race condition occurs and this stmt fails -- in those cases try to update again exception when DUP_VAL_ON_INDEX then begin difference := 0; select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; end; end; end; return difference end calcTargetTotal; This works as expected in unit tests with multiple threads never failing. However when loaded on a live system we have seen this fail with a stack trace looking like this: ORA-01403: no data found ORA-00001: unique constraint () violated ORA-01403: no data found The line numbers (which I have removed since they are meaningless out of context) verify that the first update fails due to no data, the insert fail due to uniqueness, and the 2nd update is failing with no data, which should be impossible. From what I have read on other thread a MERGE statement is also not atomic and could suffer similar problems. Does anyone have any ideas how to prevent this from occurring?

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  • c program pointer

    - by sandy101
    Hello , I am trying some programs in c face a problem with this program #include<stdio.h> int main() { int a=9,*x; float b=3.6,*y; char c='a',*z; printf("the value is %d\n",a); printf("the value is %f\n",b); printf("the value is %c\n",c); x=&a; y=&b; z=&c; printf("%u\n",a); printf("%u\n",b); printf("%u\n",c); x++; y++; z++; printf("%u\n",a); printf("%u\n",b); printf("%u\n",c); return 0; } can any one tell me what is the problem with this and i also want to know that when in the above case if the pointer value is incremented then will it over write the previous value address as suppose that the value we got in the above program (without the increment in the pointer value )is 65524 65520 65519 and after the increment the value of the pointer is 65526(as 2 increment for the int ) 65524(as 4 increment for the float ) 65520(as 1 increment for the char variable ) then if in that case will the new pointer address overwrite the content of the previous address and what value be contained at the new address ......plz help

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  • Using a Form With Variables as Part of a Function

    - by John
    Hello, Could the form below be part of a function? I am wondering if it might not be able to be part of a function since it has variables. Thanks in advance, John echo '<form action="http://www...com/sandbox/comments/comments2.php" method="post"> <input type="hidden" value="'.$_SESSION['loginid'].'" name="uid"> <input type="hidden" value="'.$submissionid.'" name="submissionid"> <input type="hidden" value="'.$submission.'" name="submission"> <input type="hidden" value="'.$url.'" name="url"> <input type="hidden" value="'.$submittor.'" name="submittor"> <input type="hidden" value="'.$submissiondate.'" name="submissiondate"> <input type="hidden" value="'.$countcomments.'" name="countcomments"> <input type="hidden" value="'.$dispurl.'" name="dispurl"> <label class="addacomment" for="title">Add a comment:</label> <textarea class="commentsubfield" name="comment" type="comment" id="comment" maxlength="1000"></textarea> <div class="commentsubbutton"><input name="submit" type="submit" value="Submit"></div> </form> ';

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  • mysql to excel genration using php

    - by pmms
    <?php // DB Connection here mysql_connect("localhost","root",""); mysql_select_db("hitnrunf_db"); $select = "SELECT * FROM jos_users "; $export = mysql_query ( $select ) or die ( "Sql error : " . mysql_error( ) ); $fields = mysql_num_fields ( $export ); for ( $i = 0; $i < $fields; $i++ ) { $header .= mysql_field_name( $export , $i ) . "\t"; } while( $row = mysql_fetch_row( $export ) ) { $line = ''; foreach( $row as $value ) { if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } header("Content-type: application/octet-stream"); header("Content-Disposition: attachment; filename=your_desired_name.xls"); header("Pragma: no-cache"); header("Expires: 0"); print "$header\n$data"; ? the above code is used for genrating mysql to excel sheet but we are getting following error the file youare trying to open, 'users.xls',is in a different format than specified by the file extension. verify that the file is not corrupted and is from a trusted source before opening the file. do you want to open the file now?

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  • Javascript inheritance: call super-constructor or use prototype chain?

    - by Jeremy S.
    Hi folks, quite recently I read about javascript call usage in MDC https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/call one linke of the example shown below, I still don't understand. Why are they using inheritance here like this Prod_dept.prototype = new Product(); is this necessary? Because there is a call to the super-constructor in Prod_dept() anyway, like this Product.call is this just out of common behaviour? When is it better to use call for the super-constructor or use the prototype chain? function Product(name, value){ this.name = name; if(value >= 1000) this.value = 999; else this.value = value; } function Prod_dept(name, value, dept){ this.dept = dept; Product.call(this, name, value); } Prod_dept.prototype = new Product(); // since 5 is less than 1000, value is set cheese = new Prod_dept("feta", 5, "food"); // since 5000 is above 1000, value will be 999 car = new Prod_dept("honda", 5000, "auto"); Thanks for making things clearer

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  • Cordova polluted logs with persistent.js add()

    - by slaver113
    I am using the latest phonegap/cordova version 2.1. and my log in Eclipse logcat get polluted with code when i do var allItems = Item.all(); allItems.list(null, function (results) { results.forEach(function (r) { console.log(r.id+ " " + r.lat + " " + r.long + " " + r.state); }); }); I get a output like (for 100s of lines) 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } at :1149822901

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  • [Concept] How does unlink() find the file to delete?

    - by Prasad
    My app has a 'Photo' field to store URL. It uses sfWidgetFormInputFileEditable for the widget schema. To delete the old image when a new image is uploaded, I use unlink before setting the value in the over-ridden setter and it works!!! if (file_exists($this->_get('photo'))) unlink($this->_get('photo')); Photos are stored in uploads/photos and when saving 'Photo' only the file name xxx-yyy.zzz is saved (and not the full path). However, I wish to know how symfony/php knows the full path of the file to be deleted? Part 2: I am using sfThumbnailPlugin to generate thumbnails. So the actual code looks like this: public function setPhoto($value) { if(!empty($value)) { Contact::generateThumbnail($value); // delete current Photo & create thumbnail $this->_set('photo',$value); // setting new value after deleting old one } } public function generateThumbnail($value) { $uploadDir = sfConfig::get('app_photo_upload'); // path to upload folder if (file_exists($this->_get('photo'))) { unlink($this->_get('photo')); // delete full-size image // path to thumbnail $thumbpath = $uploadDir.'/thumbnails/'.$this->get('photo'); // read a blog, tried setting dir manually, doesn't work :( //chdir('/thumbnails/'); // tried closing the file too, doesn't work! :( //fclose($thumbpath) or die("can't close file"); //unlink($this->_get('photo')); // doesn't work; no error :( unlink($thumbpath); // doesn't work, no error :( } $thumbnail = new sfThumbnail(150, 150); $thumbnail->loadFile($uploadDir.'/'.$value); $thumbnail->save($uploadDir.'/thumbnails/'.$value, 'image/png'); } Why can't the thumbnail be deleted using unlink()? is the sequence of ops incorrect? Is it because the old thumbnail is displayed in the sfWidgetFormInputFileEditable widget? I've spent hours trying to figure this out, but unable to nail down the real cause. Thanks in advance.

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  • jquery problem in IE working fine in FF

    - by Bharanikumar
    function populate_customer_details(){ $.ajax({ type : 'POST', url : 'populate_customer_details.php', data: { email : $('#txt_email_id').val() }, success : function(data){ if(data=="NOROWSFOUND"){ alert("Sorry, Email ID not exist in our database"); document.getElementById("txt_email_id").focus(); }else{ var val = explode_all_into_arr(data,"|=|"); document.getElementById("FirstName").value = val[0]; document.getElementById("LastName").value = val[1]; document.getElementById("mobilecountrycode").value = parseInt(val[2]); document.getElementById("MobileNo").value = val[3]; document.getElementById("homecountrycode").value = parseInt(val[4]); document.getElementById("HomeNo").value = val[5]; document.getElementById("PaxEmail").value = val[6]; document.getElementById("PaxEmailConf").value = val[6]; } }, }); } This is my snippet purpose is getting the customer details and populate into textfield and combo box , That is Firstname will append into Firstname text field , Secondname will append into Secondname text field , Same like mobilecountrycode (but this is dropdown combo), Some time combo selectedindex work fine, but some time not selecting the value , I am not sure what s problem in that... Nothing works in IE , Also showing object expected error in IE , i have ajax_common.js : in this i added above script , in the page top first i included the jquery.js , Then i include ajax_common.js file, But no idea why this problem. Regards (NOTE i included the jquery.js ) ,

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  • Why does applying this gradient style break my silverlight app ?

    - by Robotsushi
    I am having some issues with applying a gradient to a RadButton. I have a gradient definition in my styles resource dictionairy like so : <LinearGradientBrush x:Key="GridView_HeaderBackground" EndPoint="0.5,1" StartPoint="0.5,0"> <GradientStop Color="#FF5B5B5B" Offset="1"/> <GradientStop Color="#FF868686"/> <GradientStop Color="#FF4F4F4F" Offset="0.42"/> <GradientStop Color="#FF0E0E0E" Offset="0.43"/> </LinearGradientBrush> When i apply this gradient directly to the background of a RadButton everything works. Here is the button and the template definition: Button <telerik:RadButton Margin="5,10,5,0" Click="RadButton_Click" Tag="30" Content="30 Days" Style="{StaticResource SliderButton}" Background="{StaticResource GridView_HeaderBackground}" /> Template: <!-- Style Template for Slider RadButton --> <Style x:Key="SliderButton" TargetType="telerik:RadButton"> <Setter Property="Height" Value="30" /> <Setter Property="Foreground" Value="#FFFFFF" /> <Setter Property="BorderThickness" Value="0" /> <Setter Property="Margin" Value="5,2" /> </Style> However when applying this gradient in the resource dictionary, my application will not load it simply gets to the silverlight loading screen and then never proceeds Here is the button and template which breaks my app. Button: <telerik:RadButton Margin="5,10,5,0" Click="RadButton_Click" Tag="30" Content="30 Days" Style="{StaticResource SliderButton}" /> Template: <!-- Style Template for Slider RadButton --> <Style x:Key="SliderButton" TargetType="telerik:RadButton"> <Setter Property="Background" Value="{StaticResource GridView_HeaderBackground}" /> <Setter Property="Height" Value="30" /> <Setter Property="Foreground" Value="#FFFFFF" /> <Setter Property="BorderThickness" Value="0" /> <Setter Property="Margin" Value="5,2" /> </Style> When i observe the js error console in google chrome i notice the following error is produced: "Cannot find a resource with the name/key ResourceWrapper"

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  • html escape characters

    - by user1468537
    I have the following: <form name="input" method="get" action="http://site:8083/Default.aspx?DC=" target="foo" onSubmit="window.open('', 'foo', 'width=1100 height=500,status=no,resizable=yes,scrollbars=yes')"> <select name="DC"> <option value="1&Type=type1">1</option> <option value="2&Type=type2">2</option> <option value="3&Type=type3">3</option> <option value="4&Type=type4">4</option> <option value="5&Type=type5">5</option> <option value="6&Type=type6">6</option> <option value="7&Type=type7">7</option> </select> <input type="submit" value=">>"/>&nbsp;&nbsp; </form> Basically my querystring should be something like DC=1&Type=type1 the problem I have is that when I click the button above the html screws up the stirng by changing & to %26 and = to %3D How can I make the value stay as I have it in the code above?

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  • JQuery: Create n selects after choosing it in the select box

    - by Tom
    I have this select: <select name="main"> <option value="2">2s</option> <option value="3">3s</option> <option value="5">5s</option> </select> How do I make, that after choosing 2s, 2 selects would be created: <select name="select1"> <option value="0">0</option> <option value="1">1</option> <option value="2">2</option> </select> <select name="select2"> <option value="0">0</option> <option value="1">1</option> <option value="2">2</option> </select> After choosing 3s, it would create 3 selects and so on. Thanks Would appreciate jsfiddle example

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  • PHP Array to CSV

    - by JohnnyFaldo
    I'm trying to convert an array of products into a CSV file, but it doesn't seem to be going to plan. The CSV file is one long line, here is my code: for($i=0;$i<count($prods);$i++) { $sql = "SELECT * FROM products WHERE id = '".$prods[$i]."'"; $result = $mysqli->query($sql); $info = $result->fetch_array(); } $header = ''; for($i=0;$i<count($info);$i++) { $row = $info[$i]; $line = ''; for($b=0;$b<count($row);$b++) { $value = $row[$b]; if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } header("Content-type: application/octet-stream"); header("Content-Disposition: attachment; filename=your_desired_name.xls"); header("Pragma: no-cache"); header("Expires: 0"); print "$data"; Also, the header doesn't force a download. I've been copy and pasting the output and saving as .csv

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  • How do I extract specific data with preg_match?

    - by paulswansea
    I'm looking to extract values from a whole load of html (i've just trimmed down to the relevant data), there are multiple 'select' elements, and only want to extract those who's 'name' element matches the name 'aMembers'. So the resulting values I would like to retrieve are 5,10,25 and 30 (see below) how can I achieve this with preg_match? <DIV id="searchM" class="search"><select name="aMembers" id="aMembers" tabIndex="2"> <option selected="selected" value="">Data 3</option> <option value="5">A name</option> <option value="10">Another name</option> </select> </DIV> <DIV id="searchM" class="search"><select name="bMembers" id="bMembers" tabIndex="2"> <option selected="selected" value="">Data 2</option> <option value="15">A name</option> <option value="20">Another name</option> </select> </DIV> <DIV id="searchM" class="search"><select name="aMembers" id="Members" tabIndex="2"> <option selected="selected" value="">Data 1</option> <option value="25">A name</option> <option value="30">Another name</option> </select> </DIV>

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  • Deserializing child elements as attributes of parent

    - by LloydPickering
    I have XML files which I need to deserialize. I used the XSD tool from Visual Studio to create c# object files. the generated classes do deserialize the files except not in the way which I need. I would appreciate any help figuring out how to solve this problem. The child elements named 'data' should be attributes of the parent element 'task'. A shortened example of the XML is below: <task type="Nothing" id="2" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> <task type="Wait for Tasks" id="10" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> </task> <task type="Wait for Tasks" id="10" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> </task> </task> The Class definition I am trying to deserialize to is in the form: public class task { public string prerequisiteTasks {get;set;} public string exclusionTasks {get;set;} public string allowRepeats {get;set;} [System.Xml.Serialization.XmlElementAttribute("task")] public List<task> ChildTasks {get;set;} } The child 'task's are fine, but the generated files put the 'data' elements into an array of data[] rather than as named members of the task class as I need.

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  • CheckBOX ASP MVC

    - by NewmanASPMVC
    Hi i am new to ASP.NET MVC. I am not sure how to deal with Check box or Radio Button to get values when they are clicked. Can any one help me? I am providing a simple code that might help you understand what i meant to be. Please share examples. <script type="text/javascript" > function check(browser) { document.getElementById("answer").value=browser; } </script> <form action=""> <input type="radio" name="browser" onclick="check(this.value)" value="Internet Explorer"/>Internet Explorer<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Firefox"/>Firefox<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Netscape"/>Netscape<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Opera"/>Opera<br /> <br /> Your favorite browser is: <input type="text" id="answer" size="20"/> </form>

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  • Credit card validation with regexp using test()

    - by Matt
    I'm trying to complete some homework and it appears the book might have gotten it wrong. I have a simple html page that allows user to pick a credit card in our case american express. The user then enters a number and evalutes that number based on a regular expression. My question ends up being when test() evaluates the number it returns a boolean or a string? I should then compare that string or boolean? True == true should fire off the code in a nested if statement. Heres what the book gives me as valid code: if(document.forms[0].cardName.value == "American Express") { var cardProtocol = new RegExp("^3[47][0-9]{13}$"); //REGEX ENTRY HERE if(cardProtocol.test(document.forms[0].cardNumber.value)) document.forms[0].ccResult.value = "Valid credit card number"; } The above code doesn't work in firefox. I've tried modifying it with 2 alerts to make sure the number is good and the boolean is good...and still no luck: if(document.forms[0].cardName.value == "American Express") { var cardProtocol = new RegExp("^3[47][0-9]{13}$"); //REGEX ENTRY HERE <------ alert(document.forms[0].cardNumber.value) alert(cardProtocol.test(document.forms[0].cardNumber.value)) if((cardProtocol.test(document.forms[0].cardNumber.value)) == true ) // <--Problem { document.forms[0].ccResult.value = "Valid credit card number"; } else { document.forms[0].ccResult.value = "Invalid credit card number"; } } Any ideas? the if loop is the culprit but I'm not figuring out why it is not working. Please throw up the code for the if loop! Thanks for the help!

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  • jquery - how to get number from a string with mixture of letters and number

    - by Alex
    How do I use JQuery to get number from the drop down select? <select aria-invalid="false" id="RatePercent" class="wpcf7-form-control wpcf7-select ratePercent" name="RatePercent"> <option value="">---</option> <option value="Floating-6.5%">Floating-6.5%</option> <option value="6 Months-5.65%">6 Months-5.65%</option> <option value="1 Year-5.85%">1 Year-5.85%</option> <option value="18 Months-5.99%">18 Months-5.99%</option> <option value="2 Years-6.19%">2 Years-6.19%</option> <option value="3 Years-6.85%">3 Years-6.85%</option> <option value="4 Years-7.19%">4 Years-7.19%</option> <option value="5 Years-7.40%">5 Years-7.40%</option> </select> If you choose 1 Year-5.85%, it returns '5.85', instead of '1 Year-5.85%'?

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  • jQuery Time Entry with Time Navigation Keys

    - by Rick Strahl
    So, how do you display time values in your Web applications? Displaying date AND time values in applications is lot less standardized than date display only. While date input has become fairly universal with various date picker controls available, time entry continues to be a bit of a non-standardized. In my own applications I tend to use the jQuery UI DatePicker control for date entries and it works well for that. Here's an example: The date entry portion is well defined and it makes perfect sense to have a calendar pop up so you can pick a date from a rich UI when necessary. However, time values are much less obvious when it comes to displaying a UI or even just making time entries more useful. There are a slew of time picker controls available but other than adding some visual glitz, they are not really making time entry any easier. Part of the reason for this is that time entry is usually pretty simple. Clicking on a dropdown of any sort and selecting a value from a long scrolling list tends to take more user interaction than just typing 5 characters (7 if am/pm is used). Keystrokes can make Time Entry easier Time entry maybe pretty simple, but I find that adding a few hotkeys to handle date navigation can make it much easier. Specifically it'd be nice to have keys to: Jump to the current time (Now) Increase/decrease minutes Increase/decrease hours The timeKeys jQuery PlugIn Some time ago I created a small plugin to handle this scenario. It's non-visual other than tooltip that pops up when you press ? to display the hotkeys that are available: Try it Online The keys loosely follow the ancient Quicken convention of using the first and last letters of what you're increasing decreasing (ie. H to decrease, R to increase hours and + and - for the base unit or minutes here). All navigation happens via the keystrokes shown above, so it's all non-visual, which I think is the most efficient way to deal with dates. To hook up the plug-in, start with the textbox:<input type="text" id="txtTime" name="txtTime" value="12:05 pm" title="press ? for time options" /> Note the title which might be useful to alert people using the field that additional functionality is available. To hook up the plugin code is as simple as:$("#txtTime").timeKeys(); You essentially tie the plugin to any text box control. OptionsThe syntax for timeKeys allows for an options map parameter:$(selector).timeKeys(options); Options are passed as a parameter map object which can have the following properties: timeFormatYou can pass in a format string that allows you to format the date. The default is "hh:mm t" which is US time format that shows a 12 hour clock with am/pm. Alternately you can pass in "HH:mm" which uses 24 hour time. HH, hh, mm and t are translated in the format string - you can arrange the format as you see fit. callbackYou can also specify a callback function that is called when the date value has been set. This allows you to either re-format the date or perform post processing (such as displaying highlight if it's after a certain hour for example). Here's another example that uses both options:$("#txtTime").timeKeys({ timeFormat: "HH:mm", callback: function (time) { showStatus("new time is: " + time.toString() + " " + $(this).val() ); } }); The plugin code itself is fairly simple. It hooks the keydown event and checks for the various keys that affect time navigation which is straight forward. The bulk of the code however deals with parsing the time value and formatting the output using a Time class that implements parsing, formatting and time navigation methods. Here's the code for the timeKeys jQuery plug-in:/// <reference path="jquery.js" /> /// <reference path="ww.jquery.js" /> (function ($) { $.fn.timeKeys = function (options) { /// <summary> /// Attaches a set of hotkeys to time fields /// + Add minute - subtract minute /// H Subtract Hour R Add houR /// ? Show keys /// </summary> /// <param name="options" type="object"> /// Options: /// timeFormat: "hh:mm t" by default HH:mm alternate /// callback: callback handler after time assignment /// </param> /// <example> /// var proxy = new ServiceProxy("JsonStockService.svc/"); /// proxy.invoke("GetStockQuote",{symbol:"msft"},function(quote) { alert(result.LastPrice); },onPageError); ///</example> if (this.length < 1) return this; var opt = { timeFormat: "hh:mm t", callback: null } $.extend(opt, options); return this.keydown(function (e) { var $el = $(this); var time = new Time($el.val()); //alert($(this).val() + " " + time.toString() + " " + time.date.toString()); switch (e.keyCode) { case 78: // [N]ow time = new Time(new Date()); break; case 109: case 189: // - time.addMinutes(-1); break; case 107: case 187: // + time.addMinutes(1); break; case 72: //H time.addHours(-1); break; case 82: //R time.addHours(1); break; case 191: // ? if (e.shiftKey) $(this).tooltip("<b>N</b> Now<br/><b>+</b> add minute<br /><b>-</b> subtract minute<br /><b>H</b> Subtract Hour<br /><b>R</b> add hour", 4000, { isHtml: true }); return false; default: return true; } $el.val(time.toString(opt.timeFormat)); if (opt.callback) { // call async and set context in this element setTimeout(function () { opt.callback.call($el.get(0), time) }, 1); } return false; }); } Time = function (time, format) { /// <summary> /// Time object that can parse and format /// a time values. /// </summary> /// <param name="time" type="object"> /// A time value as a string (12:15pm or 23:01), a Date object /// or time value. /// /// </param> /// <param name="format" type="string"> /// Time format string: /// HH:mm (23:01) /// hh:mm t (11:01 pm) /// </param> /// <example> /// var time = new Time( new Date()); /// time.addHours(5); /// time.addMinutes(10); /// var s = time.toString(); /// /// var time2 = new Time(s); // parse with constructor /// var t = time2.parse("10:15 pm"); // parse with .parse() method /// alert( t.hours + " " + t.mins + " " + t.ampm + " " + t.hours25) ///</example> var _I = this; this.date = new Date(); this.timeFormat = "hh:mm t"; if (format) this.timeFormat = format; this.parse = function (time) { /// <summary> /// Parses time value from a Date object, or string in format of: /// 12:12pm or 23:01 /// </summary> /// <param name="time" type="any"> /// A time value as a string (12:15pm or 23:01), a Date object /// or time value. /// /// </param> if (!time) return null; // Date if (time.getDate) { var t = {}; var d = time; t.hours24 = d.getHours(); t.mins = d.getMinutes(); t.ampm = "am"; if (t.hours24 > 11) { t.ampm = "pm"; if (t.hours24 > 12) t.hours = t.hours24 - 12; } time = t; } if (typeof (time) == "string") { var parts = time.split(":"); if (parts < 2) return null; var time = {}; time.hours = parts[0] * 1; time.hours24 = time.hours; time.mins = parts[1].toLowerCase(); if (time.mins.indexOf("am") > -1) { time.ampm = "am"; time.mins = time.mins.replace("am", ""); if (time.hours == 12) time.hours24 = 0; } else if (time.mins.indexOf("pm") > -1) { time.ampm = "pm"; time.mins = time.mins.replace("pm", ""); if (time.hours < 12) time.hours24 = time.hours + 12; } time.mins = time.mins * 1; } _I.date.setMinutes(time.mins); _I.date.setHours(time.hours24); return time; }; this.addMinutes = function (mins) { /// <summary> /// adds minutes to the internally stored time value. /// </summary> /// <param name="mins" type="number"> /// number of minutes to add to the date /// </param> _I.date.setMinutes(_I.date.getMinutes() + mins); } this.addHours = function (hours) { /// <summary> /// adds hours the internally stored time value. /// </summary> /// <param name="hours" type="number"> /// number of hours to add to the date /// </param> _I.date.setHours(_I.date.getHours() + hours); } this.getTime = function () { /// <summary> /// returns a time structure from the currently /// stored time value. /// Properties: hours, hours24, mins, ampm /// </summary> return new Time(new Date()); h } this.toString = function (format) { /// <summary> /// returns a short time string for the internal date /// formats: 12:12 pm or 23:12 /// </summary> /// <param name="format" type="string"> /// optional format string for date /// HH:mm, hh:mm t /// </param> if (!format) format = _I.timeFormat; var hours = _I.date.getHours(); if (format.indexOf("t") > -1) { if (hours > 11) format = format.replace("t", "pm") else format = format.replace("t", "am") } if (format.indexOf("HH") > -1) format = format.replace("HH", hours.toString().padL(2, "0")); if (format.indexOf("hh") > -1) { if (hours > 12) hours -= 12; if (hours == 0) hours = 12; format = format.replace("hh", hours.toString().padL(2, "0")); } if (format.indexOf("mm") > -1) format = format.replace("mm", _I.date.getMinutes().toString().padL(2, "0")); return format; } // construction if (time) this.time = this.parse(time); } String.prototype.padL = function (width, pad) { if (!width || width < 1) return this; if (!pad) pad = " "; var length = width - this.length if (length < 1) return this.substr(0, width); return (String.repeat(pad, length) + this).substr(0, width); } String.repeat = function (chr, count) { var str = ""; for (var x = 0; x < count; x++) { str += chr }; return str; } })(jQuery); The plugin consists of the actual plugin and the Time class which handles parsing and formatting of the time value via the .parse() and .toString() methods. Code like this always ends up taking up more effort than the actual logic unfortunately. There are libraries out there that can handle this like datejs or even ww.jquery.js (which is what I use) but to keep the code self contained for this post the plugin doesn't rely on external code. There's one optional exception: The code as is has one dependency on ww.jquery.js  for the tooltip plugin that provides the small popup for all the hotkeys available. You can replace that code with some other mechanism to display hotkeys or simply remove it since that behavior is optional. While we're at it: A jQuery dateKeys plugIn Although date entry tends to be much better served with drop down calendars to pick dates from, often it's also easier to pick dates using a few simple hotkeys. Navigation that uses + - for days and M and H for MontH navigation, Y and R for YeaR navigation are a quick way to enter dates without having to resort to using a mouse and clicking around to what you want to find. Note that this plugin does have a dependency on ww.jquery.js for the date formatting functionality.$.fn.dateKeys = function (options) { /// <summary> /// Attaches a set of hotkeys to date 'fields' /// + Add day - subtract day /// M Subtract Month H Add montH /// Y Subtract Year R Add yeaR /// ? Show keys /// </summary> /// <param name="options" type="object"> /// Options: /// dateFormat: "MM/dd/yyyy" by default "MMM dd, yyyy /// callback: callback handler after date assignment /// </param> /// <example> /// var proxy = new ServiceProxy("JsonStockService.svc/"); /// proxy.invoke("GetStockQuote",{symbol:"msft"},function(quote) { alert(result.LastPrice); },onPageError); ///</example> if (this.length < 1) return this; var opt = { dateFormat: "MM/dd/yyyy", callback: null }; $.extend(opt, options); return this.keydown(function (e) { var $el = $(this); var d = new Date($el.val()); if (!d) d = new Date(1900, 0, 1, 1, 1); var month = d.getMonth(); var year = d.getFullYear(); var day = d.getDate(); switch (e.keyCode) { case 84: // [T]oday d = new Date(); break; case 109: case 189: d = new Date(year, month, day - 1); break; case 107: case 187: d = new Date(year, month, day + 1); break; case 77: //M d = new Date(year, month - 1, day); break; case 72: //H d = new Date(year, month + 1, day); break; case 191: // ? if (e.shiftKey) $el.tooltip("<b>T</b> Today<br/><b>+</b> add day<br /><b>-</b> subtract day<br /><b>M</b> subtract Month<br /><b>H</b> add montH<br/><b>Y</b> subtract Year<br/><b>R</b> add yeaR", 5000, { isHtml: true }); return false; default: return true; } $el.val(d.formatDate(opt.dateFormat)); if (opt.callback) // call async setTimeout(function () { opt.callback.call($el.get(0),d); }, 10); return false; }); } The logic for this plugin is similar to the timeKeys plugin, but it's a little simpler as it tries to directly parse the date value from a string via new Date(inputString). As mentioned it also uses a helper function from ww.jquery.js to format dates which removes the logic to perform date formatting manually which again reduces the size of the code. And the Key is… I've been using both of these plugins in combination with the jQuery UI datepicker for datetime values and I've found that I rarely actually pop up the date picker any more. It's just so much more efficient to use the hotkeys to navigate dates. It's still nice to have the picker around though - it provides the expected behavior for date entry. For time values however I can't justify the UI overhead of a picker that doesn't make it any easier to pick a time. Most people know how to type in a time value and if they want shortcuts keystrokes easily beat out any pop up UI. Hopefully you'll find this as useful as I have found it for my code. Resources Online Sample Download Sample Project © Rick Strahl, West Wind Technologies, 2005-2011Posted in jQuery  HTML   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Automatic Properties, Collection Initializers, and Implicit Line Continuation support with VB 2010

    - by ScottGu
    [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] This is the eighteenth in a series of blog posts I’m doing on the upcoming VS 2010 and .NET 4 release. A few days ago I blogged about two new language features coming with C# 4.0: optional parameters and named arguments.  Today I’m going to post about a few of my favorite new features being added to VB with VS 2010: Auto-Implemented Properties, Collection Initializers, and Implicit Line Continuation support. Auto-Implemented Properties Prior to VB 2010, implementing properties within a class using VB required you to explicitly declare the property as well as implement a backing field variable to store its value.  For example, the code below demonstrates how to implement a “Person” class using VB 2008 that exposes two public properties - “Name” and “Age”:   While explicitly declaring properties like above provides maximum flexibility, I’ve always found writing this type of boiler-plate get/set code tedious when you are simply storing/retrieving the value from a field.  You can use VS code snippets to help automate the generation of it – but it still generates a lot of code that feels redundant.  C# 2008 introduced a cool new feature called automatic properties that helps cut down the code quite a bit for the common case where properties are simply backed by a field.  VB 2010 also now supports this same feature.  Using the auto-implemented properties feature of VB 2010 we can now implement our Person class using just the code below: When you declare an auto-implemented property, the VB compiler automatically creates a private field to store the property value as well as generates the associated Get/Set methods for you.  As you can see above – the code is much more concise and easier to read. The syntax supports optionally initializing the properties with default values as well if you want to: You can learn more about VB 2010’s automatic property support from this MSDN page. Collection Initializers VB 2010 also now supports using collection initializers to easily create a collection and populate it with an initial set of values.  You identify a collection initializer by declaring a collection variable and then use the From keyword followed by braces { } that contain the list of initial values to add to the collection.  Below is a code example where I am using the new collection initializer feature to populate a “Friends” list of Person objects with two people, and then bind it to a GridView control to display on a page: You can learn more about VB 2010’s collection initializer support from this MSDN page. Implicit Line Continuation Support Traditionally, when a statement in VB has been split up across multiple lines, you had to use a line-continuation underscore character (_) to indicate that the statement wasn’t complete.  For example, with VB 2008 the below LINQ query needs to append a “_” at the end of each line to indicate that the query is not complete yet: The VB 2010 compiler and code editor now adds support for what is called “implicit line continuation support” – which means that it is smarter about auto-detecting line continuation scenarios, and as a result no longer needs you to explicitly indicate that the statement continues in many, many scenarios.  This means that with VB 2010 we can now write the above code with no “_” at all: The implicit line continuation feature also works well when editing XML Literals within VB (which is pretty cool). You can learn more about VB 2010’s Implicit Line Continuation support and many of the scenarios it supports from this MSDN page (scroll down to the “Implicit Line Continuation” section to find details). Summary The above three VB language features are but a few of the new language and code editor features coming with VB 2010.  Visit this site to learn more about some of the other VB language features coming with the release.  Also subscribe to the VB team’s blog to learn more and stay up-to-date with the posts they the team regularly publishes. Hope this helps, Scott

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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