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• jQuery ajax response not operating correctly

  - by mmarceau

  Ok this is frustrating... The code below works "correctly" as far as sending the email address to the SaveEmail URL and it gets saved correctly each time I change the drop down. However it only outputs the "Successful" message once, no matter how many times I change the value in the drop down. The "data" that is returned is "Successful". I would like to show the message for a couple seconds, then fade it out. It works correctly the first time I change the drop down, after that the change happens and the value gets saved, but the "Successful" message doesn't display. jQuery code: $('#AgentEmails').change(function() { var NewAddress = $('#AgentEmails').val(); $.post('SaveEmail.aspx', { email: NewAddress }, function(data) { $('#SelectMsg').html("<b>" + data + "</b>").fadeOut(); }); }); HTML code: <select ID='AgentEmails' runat='server'> <option value="[email protected]">TEST</option> </select><span id='SelectMsg'></span> What needs to be changed in my code to make this operate correctly? Thanks for the help.

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• How to implement a grapher in C#

  - by iansinke

  So I'm writing a graphing calculator. So far I have a semi-functional grapher, however, I'm having a hard time getting a good balance between accurate graphs and smooth looking curves. The current implementation (semi-pseudo-code) looks something like this: for (float i = GraphXMin; i <= GraphXMax; i++) { PointF P = new PointF(i, EvaluateFunction(Function, i) ListOfPoints.Add(P) } Graphics.DrawCurve(ListOfPoints) The problem with this is since it only adds a point at every integer value, graphs end up distorted when their turning points don't fall on integers (e.g. sin(x)^2). I tried incrementing i by something smaller (like 0.1), which works, but the graph looks very rough. I am using C# and GDI+. I have SmoothingMethod set to AntiAlias, so that's not the problem, as you can see from the first graph. Is there some sort of issue with drawing curves with a lot of points? Should the points perhaps be positioned exactly on pixels? I'm sure some of you have worked on something very similar before, so any suggestions? While you're at it, do you have any suggestions for graphing functions with asymptotes? e.g. 1/x^2 P.S. I'm not looking for a library that does all this - I want to write it myself.

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• C++ template type deduction problem

  - by hamishmcn

  motivation: I would like to create a utility class so that instead of having to write: if( someVal == val1 || someVal == val2 || someVal == val3 ) I could instead write: if( is(someVal).in(val1, val2, val3) ) which is much closer to the mathematical 'a is an element of (b,c,d)' and also would save on a lot of typing when the variable name 'someVal' is long. Here is the code I have so far (for 2 and 3 values): template<class T> class is { private: T t_; public: is(T t) : t_(t) { } bool in(const T& v1, const T& v2) { return t_ == v1 || t_ == v2; } bool in(const T& v1, const T& v2, const T& v3) { return t_ == v1 || t_ == v2 || t_ == v3; } }; However it fails to compile if I write: is(1).in(3,4,5); instead I have to write is<int>(1).in(3,4,5); Which isn't too bad, but it would be better if somehow the compiler could figure out that the type is int with out me having to explicitly specify it. Is there anyway to do this or I am stuck with specifying it explicitly?

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• how to add data in Table of Jasper Report using Java

  - by Areeb Gillani

  i am here to ask you just a simple question that i am trying to pass data to a jasper report using java but i dont know how to to, because the table data is very dynamic thats y cannot pass sql query. any idea for this. i have a 2D array of object type, where i have all the data... so how can i pass that... Thanx in advance...!:) ConnectionManager con = new ConnectionManager(); con.establishConnection(); String fileName = "Pmc_Bill.jrxml"; String outFileName = "OutputReport.pdf"; HashMap params = new HashMap(); params.put("PName", pname); params.put("PSerial", psrl); params.put("PGender",pgen); params.put("PPhone",pph); params.put("PAge",page); params.put("PRefer",pref); params.put("PDateR",dateNow); try { JasperReport jasperReport = JasperCompileManager.compileReport(fileName); if(jasperReport != null ) System.out.println("so far so good "); // Fill the report using an empty data source JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, params, new JRTableModelDataSource(tbl.getModel()));//con.connection); try{ JasperExportManager.exportReportToPdfFile(jasperPrint, outFileName); System.out.printf("File exported sucessfully"); }catch(Exception e){ e.printStackTrace(); } JasperViewer.viewReport(jasperPrint); } catch (JRException e) { JOptionPane.showMessageDialog(null, e); e.printStackTrace(); System.exit(1); }

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• Many tables for many users?

  - by Seagull

  I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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• No results are returned when using Flickr JSON request

  - by Martijn1981

  I'm still fairly new to AJAX and I'm experimenting with Twitter and Flickr. Twitter is working fine so far, but I've run into some issues with the Flickr API. I'm getting no results back. The URL seems to be working fine and I'm pointing to the right object containing the array ('items'). Can anybody tell me what I'm doing wrong please? Thanks! $('#show_pictures').click(function(e){ e.preventDefault(); $.ajax({ url: 'http://api.flickr.com/services/feeds/photos_public.gne?format=json&jsoncallback=?&tags=home', dataType: 'jsonp', success: function(data) { $.each(data.items, function(i, item){ $('<div></div>') .hide() .append('<h1>'+item.title+'</h1>') .append('<img src="'+item.media.m+'" >') .append('<p>'+item.description+'</p>') .appendTo('#results') .fadeIn(); }) }, error: function(data) { alert('Something went wrong!'); } }); });

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• Passing System classes as constructor parameters

  - by mcl

  This is probably crazy. I want to take the idea of Dependency Injection to extremes. I have isolated all System.IO-related behavior into a single class so that I can mock that class in my other classes and thereby relieve my larger suite of unit tests of the burden of worrying about the actual file system. But the File IO class I end up with can only be tested with integration tests, which-- of course-- introduces complexity I don't really want to deal with when all I really want to do is make sure my FileIO class calls the correct System.IO stuff. I don't need to integration test System.IO. My FileIO class is doing more than simply wrapping System.IO functions, every now and then it does contain some logic (maybe this is the problem?). So what I'd like is to be able to test my File IO class to ensure that it makes the correct system calls by mocking the System.IO classes themselves. Ideally this would be as easy as having a constructor like so: public FileIO( System.IO.Directory directory, System.IO.File file, System.IO.FileStream fileStream ) { this.Directory = directory; this.File = file; this.FileStream = fileStream; } And then calling in methods like: public GetFilesInFolder(string folderPath) { return this.Directory.GetFiles(folderPath) } But this doesn't fly since the System.IO classes in question are static classes. As far as I can tell they can neither be instantiated in this way or subclassed for the purposes of mocking.

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• Randomly Position A Div

  - by Connie

  I'm looking for a way to randomly position a div anywhere on a page (ONCE per load). I'm currently programming a PHP-based fantasy pet simulation game. One of the uncommon items on the game is a "Four Leaf Clover." Currently, users gain "Four Leaf Clovers" through random distribution - but I would like to change that (it's not interactive enough!). What I Am Trying To Do: The idea is to make users search for these "Four Leaf Clovers" by randomly placing this image anywhere on the page: (my rendition of a four leaf clover) I'd like to do this using a Java/Ajax script that generates a div, and then places it anywhere on the page. And does not move it once it's been placed, until the page is reloaded. I've tried so many Google searches, and the closest thing that I've found so far is this (click), from this question. But, removing the .fadein, .delay, and .fadeout stopped the script from working entirely. I'm not by any means a pro with Ajax. Is what I'm trying to do even possible?

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• Why do I need to give my options a value attribute in my dropdown? JQuery related.

  - by Alex

  So far in my web developing experiences, I've noticed that almost all web developers/designers choose to give their options in a select a value like so: <select name="foo"> <option value="bar">BarCheese</option> // etc. // etc. </select> Is this because it is best practice to do so? I ask this because I have done a lot of work with jQuery and dropdown's lately, and sometimes I get really annoyed when I have to check something like: $('select[name=foo]').val() == "bar"); To me, many times that seems less clear than just being able to check the val() against BarCheese. So why is it that most web developers/designers specify a value paramater instead of just letting the options actual value be its value? And yes, if the option has a value attribute I know I can do something like this: $('select[name=foo] option:contains("BarCheese")').attr('selected', 'selected'); But I would still really like to know why this is done. Thanks!!

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• In Gtk#, why might VALID_ITER fail even after I check it with IterIsValid?

  - by Matthew

  I have a convenience function in my TreeView that looks something like this: Card GetCardFromPath (TreePath path) { TreeIter iter; if (path == null || !Model.GetIter (out iter, path)) return null; if ((Model as TreeModelSort).IterIsValid (iter)) return (Card) Model.GetValue (iter, 0); return null; } Most of the time this works without any errors. But when it is called directly after the Model is changed, line 8 gives me these Gtk runtime errors: [Fatal 16:53:02.448] [Gtk] gtk_list_store_get_value: assertion `VALID_ITER (iter, list_store)' failed [Fatal 16:53:02.449] [GLib-GObject] g_value_unset: assertion `G_IS_VALUE (value)' failed As far as I can tell, I shouldn't even need to check IterIsValid, because I'm already checking the return value of Model.GetIter. Even so, how can VALID_ITER fail in a function that only gets called if IterIsValid returns true? If it makes a difference, the Model is a TreeModelSort, which sorts a TreeModelFilter, which filters a ListStore. The error occurs when GetCardFromPath is called from HandleSelectionChanged when multiple rows have just been removed from the ListStore. It doesn't seem to prevent anything from working properly, but having a cascade of errors whenever I remove multiple rows isn't really ideal.

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• c# warn if text box is empty or contains a non-whole number

  - by Jamaul Smith

  In my specific case, I need the value in propertyPriceTextBox to be numeric only, and a whole number. A value also has to be entered, and I can just Messagebox.Show() a warning and that's all I'd need to do. This is what I have so far. private void computeButton_Click(object sender, EventArgs e) { decimal propertyPrice; if ((decimal.TryParse(propertyPriceTextBox.Text, out propertyPrice))) decimal.Parse(propertyPriceTextBox.Text); { if (residentialRadioButton.Checked == true) commisionLabel.Text = (residentialCom * propertyPrice).ToString("c"); if (commercialRadioButton.Checked == true) commisionLabel.Text = (commercialCom * propertyPrice).ToString("c"); if (hillsRadioButton.Checked == true) countySalesTaxTextBox.Text = ( hilssTax * propertyPrice).ToString("c"); if (pascoRadioButton.Checked == true) countySalesTaxTextBox.Text = (pascoTax * propertyPrice).ToString("c"); if (polkRadioButton.Checked == true) countySalesTaxTextBox.Text = (polkTax * propertyPrice).ToString("c"); decimal result; result = (countySalesTaxTextBox.Text + stateSalesTaxTextBox.Text + propertyPriceTextBox.Text + comissionTextBox.Text).ToString("c"); } else (.) MessageBox.Show("Property Price must be a whole number."); }

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• Quickly accessing files in a 'project'

  - by bbbscarter

  Hi all. I'm looking for a way to quickly open files in my project's source tree. What I've been doing so far is adding files to the file-name-cache like so: (file-cache-add-directory-recursively (concat project-root "some/sub/folder") ".*\\.\\(py\\)$") after which I can use anything-for-files to access any file in the source tree with about 4 keystrokes. Unfortunately, this solution started falling over today. I've added another folder to the cache and emacs has started running out of memory. What's weird is that this folder contains less than 25% of files I'm adding, and yet emacs memory use goes up from 20mb to 400mb on adding just this folder. The total number of files is around 2000, so this memory use seems very high. Presumably I'm abusing the file cache. Anyway, what do other people do for this? I like this solution for its simplicity and speed; I've looked at some of the many, many project management packages for emacs and none of them really grabbed me... Thanks in advance! Simon

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• Determine if a Range contains a value

  - by Brad Dwyer

  I'm trying to figure out a way to determine if a value falls within a Range in Swift. Basically what I'm trying to do is adapt one of the examples switch statement examples to do something like this: let point = (1, -1) switch point { case let (x, y) where (0..5).contains(x): println("(\(x), \(y)) has an x val between 0 and 5.") default: println("This point has an x val outside 0 and 5.") } As far as I can tell, there isn't any built in way to do what my imaginary .contains method above does. So I tried to extend the Range class. I ended up running into issues with generics though. I can't extend Range<Int> so I had to try to extend Range itself. The closest I got was this but it doesn't work since >= and <= aren't defined for ForwardIndex extension Range { func contains(val:ForwardIndex) -> Bool { return val >= self.startIndex && val <= self.endIndex } } How would I go about adding a .contains method to Range? Or is there a better way to determine whether a value falls within a range? Edit2: This seems to work to extend Range extension Range { func contains(val:T) -> Bool { for x in self { if(x == val) { return true } } return false } } var a = 0..5 a.contains(3) // true a.contains(6) // false a.contains(-5) // false I am very interested in the ~= operator mentioned below though; looking into that now.

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• Intelligent Merge of two Arrays (3-way-kindof)

  - by simon.oberhammer

  I have to Arrays, each represents a list of Stories. Two users can concurrently modify the order, add or remove Stories, and I want those changes merged. An example should make this clearer Orignial 1,2,3,4,5 UserA (mine) 3,1,2,4,5 (moved story 3 to start) UserB (theirs) 1,2,3,5,4 (moved story 5 forward) The result of the above should be Merge (result) 3,1,2,5,4 In case of conflicts, UserA should always win. I came pretty far with this simple approach. First i deleted whatever mine says i should deleted (that part of the code is not shown, it's trivial), then I iterate of mine, inserting and moving from theirs what is needed (mstories = mine, tstories = theirs): var offset = 0; for (var idx=0;idx<mstories.length;idx++) { var storyId = mstories[idx]; // new story in theirs if (mstories.indexOf(tstories[idx]) == -1) { mstories.splice(idx+1, 0, tstories[idx]); idx--; continue; } // new story in mine? if (tstories.indexOf(storyId) == -1) { tstories.splice(idx+offset, 0, storyId); offset += 1; // story moved } else if (tstories.indexOf(storyId) != idx + offset) { tstories.splice(tstories.indexOf(storyId), 1); tstories.splice(idx+offset, 0, storyId); } } It's close, but it gets confused when too many Stories are moved to the front / back with Stories in between, which the other User touched. I have an extended version which does checks on the original and is smarter - holding 2 offsets, etc - , but I feel like this is a problem that must have a) a name b) a perfect solution and i don't want to re-invent it.

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• Howto open a file and remove the last line?

  - by sologhost

  I am looking to open up a file, grab the last line in the file where the line = "?", which is the closing tag for a php document. Than I am wanting to append data into it and add back in the "?" to the very last line. I've been trying a few approaches, but I'm not having any luck. Here's what I got so far, as I am reading from a zip file. Though I know this is all wrong, just needing some help with this please... // Open for reading is all we can do with zips and is all we need. if (zip_entry_open($zipOpen, $zipFile, "r")) { $fstream = zip_entry_read($zipFile, zip_entry_filesize($zipFile)); $fp = fopen($curr_lang_file, 'r+b'); while (!feof($fp)) { $output = fgets($fp, 16384); if (trim($output) == '?>') break; fwrite($fp, $output); } fclose($fp); file_put_contents($curr_lang_file, $fstream, FILE_APPEND); } $curr_lang_file is a filepath string to the actual file that needs to have the fstream appended to it, but after we remove the last line that equals '?'

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• Sync data between a windows desktop app and windows mobile client app

  - by Chris W

  I need to knock up a very quick prototype/proof of concept application to demo to someone within the next couple of days so I've minimal time to research this as fully as I normally would. The set-up is a very simple database application running on a laptop - will only ever be a single user updating a couple of tables so I was thinking of knocking up a basic Win Forms app against SQL Compact. Visual Studio's auto generated data grid edit screens will be fine with a little customisation. The second aspect is to then add a windows mobile client application that can pull data from both tables stored on the laptop, edit some data and insert some extra rows before sending the changes back to the laptop copy of the database. I've not done any WinMo development so what's the best approach for me to look at. Is it easy enough to sync data between the two databases when the WinMo device is connected to the laptop with USB? Most of the samples I've looked at so far seem to be syncing SQL Compact with SQL Standard using IIS which seems a bit overkill. The volumes of data to be synced are so small that I can easily write some manual sync code if it's easy for me to query/update the Compact DB from the laptop application when the device is connected.

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• C preprocessor problem in Microsoft Visual Studio 2010

  - by Remo.D

  I've encountered a problem with the new Visual C++ in VS 2010. I've got a header with the following defines: #define STC(y) #y #define STR(y) STC(\y) #define NUM(y) 0##y The intent is that you can have some constant around like #define TOKEN x5A and then you can have the token as a number or as a string: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\x5A" This is the expected behavior under the the substitution rules of macros arguments and so far it has worked well with gcc, open watcom, pellesC (lcc), Digital Mars C and Visual C++ in VS2008 Express. Today I recompiled the library with VS2010 Express only to discover that it doesn't work anymore! Using the new version I would get: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\y" It seems that the new preprocessor treats \y as an escape sequence even within a macro body which is a non-sense as escape sequences only have a meaning in literal strings. I suspect this is a gray area of the ANSI standard but even if the original behavior was mandated by the standard, MS VC++ is not exactly famous to be 100% ANSI C compliant so I guess I'll have to live with the new behavior of the MS compiler. Given that, does anybody have a suggestion on how to re-implement the original macros behavior with VS2010?

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• Building simple jQuery plugin, need assistance

  - by kirisu_kun

  Hi there, I'm building my first ever jQuery plugin (it's just a simple experiment). Here's what I have so far: (function($){ $.fn.extend({ auchieFader: function(options) { var defaults = { mask: '', topImg : '', } var options = $.extend(defaults, options); return this.each(function() { var o = options; var obj = $(this); var masker = $(o.mask, obj); masker.hover(function () { $(o.topImg).stop().animate({ "opacity": "0" }, "slow"); }, function () { $(o.topImg).stop().animate({ "opacity": "1" }, "slow"); }); }); } }); })(jQuery); I'm then calling the plugin using: $('.fader').auchieFader({mask: ".mask", topImg: ".top"}); If I then add another request say: $('.fader2').auchieFader({mask: ".mask", topImg: ".top"}); Then no matter what instance of my 2 faders I hover both of them will trigger. I know this is because my mask mask and topImg options have the same class - but how can I modify the plugin to allow for these items to have the same class? I know it's probably something really simple, but I'm still finding my way with jQuery and Javascript in general. Any other tips on improving my code would also be greatly appreciated! Cheers, Chris

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• firefox does not load large size images

  - by Pradeep

  I am stuck with a kind of bug in FF, wherein it’s unable to load images of big size (I have 8 MB size of image) from the server. The loading of image is all fine on IE. I am still looking out for ways to get rid of this problem. I changed server(IIS) settings to allow bigger file sizes. Also, I used “load” event on image using JQuery and tried all sort of options listed here http://api.jquery.com/load-event/, but nothing worked so far. If anyone of you has come across any such similar problem, and a way to resolve it, it would be nice to hear from you Please note: high resolution images are part of the requirement. Code : <style> img { background-color: #FFFFFF; background-image: url(http://eremurus.hyd:8080/QMS/plugin/imagepanner/loader.gif); background-repeat: no-repeat; background-position: center center; } </style> <script src="../plugin/jquery-ui-1.8.7.custom/js/jquery-1.4.4.min.js" type="text/javascript"></script> <script> jQuery(document).ready(function($){ ///var _url = "http://eremurus.hyd:8080/QMS/plugin/imagepanner/floorPlan.jpg"; // set up the node / element _im =$("#main"); //_im.bind("load",function(){ $(this).fadeIn(); }); // set the src attribute now, after insertion to the DOM //_im.attr('src',_url); $("#main").one("load",function(){ alert('loaded'); }) .each(function(){ if(this.complete){ $(this).trigger("load"); } }); }); </script> </head> <body> <div id="target"><img id='main' src="http://eremurus.hyd:8080/QMS/plugin/imagepanner/floorPlan.jpg"> </img></div> </body> </html>

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• PHP: Three item validation comparison

  - by DavidYell

  I have 3 featured product panels on the homepage, and I'm writing a CMS page for it. I'm trying to validate the items. They are selected via three <select> elements, featured1, featured2 and featured3. The default is <option value="0" selected>Select an element</option> I need to validate the $_POST to ensure that the user hasn't selected the same product for more than one of the panels. I have worked out that each $_POST needs to be $_POST['featuredN'] > 0 but I can't seem to find a logical way of processing the 7 potential outcomes. Using a logic table, where 1 is a set value. 1 2 3 ------- 0 0 0 1 1 1 1 0 0 0 1 0 0 0 1 1 1 0 0 1 1 If an item is 0, then I will not update it, but I want the user to be able to update a single item if needs be. I cannot find a logical way to see if the item is not 0, and then compare it to another item if that also is not 0. So far my colleague suggested, adding up the values. Which works to see if condition 1 0 0 0 is not met. I have a vague feeling that some form of recursive function might be in order, but I can't quite get my brain to help me on this one! So to the collective brain! :)

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• Why does this SELECT ... JOIN statement return no results?

  - by Stephen

  I have two tables: 1. tableA is a list of records with many columns. There is a timestamp column called "created" 2. tableB is used to track users in my application that have locked a record in tableA for review. It consists of four columns: id, user_id, record_id, and another timestamp collumn. I'm trying to select up to 10 records from tableA that have not been locked by for review by anyone in tableB (I'm also filtering in the WHERE clause by a few other columns from tableA like record status). Here's what I've come up with so far: SELECT tableA.* FROM tableA LEFT OUTER JOIN tableB ON tableA.id = tableB.record_id WHERE tableB.id = NULL AND tableA.status = 'new' AND tableA.project != 'someproject' AND tableA.created BETWEEN '1999-01-01 00:00:00' AND '2010-05-06 23:59:59' ORDER BY tableA.created ASC LIMIT 0, 10; There are currently a few thousand records in tableA and zero records in tableB. There are definitely records that fall between those timestamps, and I've verified this with a simple SELECT * FROM tableA WHERE created BETWEEN '1999-01-01 00:00:00' AND '2010-05-06 23:59:59' The first statement above returns zero rows, and the second one returns over 2,000 rows.

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• Best way to do one-to-many "JOIN" in CouchDB

  - by mit

  There are CouchDB documents that are list elements: { "type" : "el", "id" : "1", "content" : "first" } { "type" : "el", "id" : "2", "content" : "second" } { "type" : "el", "id" : "3", "content" : "third" } There is one document that defines the list: { "type" : "list", "elements" : ["2","1"] , "id" : "abc123" } As you can see the third element was deleted, it is no longer part of the list. So it must not be part of the result. Now I want a view that returns the content elements including the right order. The result could be: { "content" : ["second", "first"] } In this case the order of the elements is already as it should be. Another possible result: { "content" : [{"content" : "first", "order" : 2},{"content" : "second", "order" : 1}] } I started writing the map function: map = function (doc) { if (doc.type === 'el') { emit(doc.id, {"content" : doc.content}); //emit the id and the content exit; } if (doc.type === 'list') { for ( var i=0, l=doc.elements.length; i<l; ++i ){ emit(doc.elements[i], { "order" : i }); //emit the id and the order } } } This is as far as I can get. Can you correct my mistakes and write a reduce function? Remember that the third document must not be part of the result. Of course you can write a different map function also. But the structure of the documents (one definig element document and an entry document for each entry) cannot be changed.

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• Download Remote File

  - by Abs

  Hello all, I have a function that will be passed in a link. The link is to a remote image. I thought I could just use the extension of the file in the URL to determine the type of image but some URLs won't have extensions in the URL. They probably just push headers to the browser and therefore I do not have an extension to parse from the URL. How can I test if the URL has an extension and if not then read the headers to determine the file type? Am I over complicating things here? Is there an easier way to do this? I am making use of Codeigniter maybe there is something already built in to do this? All I really want to do is download an image from a URL with the correct extension. This is what I have so far. function get_image($image_link){ $remoteFile = $image_link; $ext = ''; //some URLs might not have an extension $file = fopen($remoteFile, "r"); if (!$file) { return false; }else{ $line = ''; while (!feof ($file)) { $line .= fgets ($file, 4096); } $file_name = time().$ext; file_put_contents($file_name, $line); } fclose($file); } Thanks all for any help

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• Hashing 11 byte unique ID to 32 bits or less

  - by MoJo

  I am looking for a way to reduce a 11 byte unique ID to 32 bits or fewer. I am using an Atmel AVR microcontroller that has the ID number burned in at the factory, but because it has to be transmitted very often in a very low power system I want to reduce the length down to 4 bytes or fewer. The ID is guaranteed unique for every microcontroller. It is made up of data from the manufacturing process, basically the coordinates of the silicone on the wafer and the production line that was used. They look like this: 304A34393334-16-11001000 314832383431-0F-09000C00 Obviously the main danger is that by reducing these IDs they become non-unique. Unfortunately I don't have a large enough sample size to test how unique these numbers are. Having said that because there will only be tens of thousands of devices in use and there is secondary information that can be used to help identify them (such as their approximate location, known at the time of communication) collisions might not be too much of an issue if they are few and far between. Is something like MD5 suitable for this? My concern is that the data being hashed is very short, just 11 bytes. Do hash functions work reliably on such short data?

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