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• A logical problem with two tables

  - by Luke

  Hey guys, I created a list for fixtures. $result = mysql_query("SELECT date FROM ".TBL_FIXTURES." WHERE compname = '$comp_name' GROUP BY date"); $i = 1; $d = "Start"; while ($row = mysql_fetch_assoc($result)) { $odate = $row['date']; $date=date("F j Y", $row['date']); echo "<p>Fixture $i - $d to $date</p>"; } As you can see from the query, the date is displayed from the fixtures table. The way my system works is that when a fixture is "played", it is removed from this table. Therefore when the entire round of fixtures are complete, there wont be any dates for that round in this table. They will be in another table. Is there anyway I can run an other query for dates at the same time, and display only dates from the fixtures table if there isnt a date in the results table? "SELECT * FROM ".TBL_CONF_RESULTS." WHERE compid = '$_GET[id]' && type2 = '2' ORDER BY date" That would be the second query!

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• STLifying C++ classes

  - by shambulator

  I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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• restrict duplicate rows in specific columns in mysql

  - by JPro

  I have a query like this : select testset, count(distinct results.TestCase) as runs, Sum(case when Verdict = "PASS" then 1 else 0 end) as pass, Sum(case when Verdict <> "PASS" then 1 else 0 end) as fails, Sum(case when latest_issue <> "NULL" then 1 else 0 end) as issues, Sum(case when latest_issue <> "NULL" and issue_type = "TC" then 1 else 0 end) as TC_issues from results join testcases on results.TestCase = testcases.TestCase where platform = "T1_PLATFORM" AND testcases.CaseType = "M2" and testcases.dummy <> "flag_1" group by testset order by results.TestCase The result set I get is : testset runs pass fails issues TC_issues T1 66 125 73 38 33 T2 18 19 16 16 15 T3 57 58 55 55 29 T4 52 43 12 0 0 T5 193 223 265 130 22 T6 23 12 11 0 0 My problem is, this is a result table which has testcases running multiple times. So, I am able to restrict the runs using the distinct TestCases but when I want the pass and fails, since I am using case I am unable to eliminate the duplicates. Is there any way to achieve what I want? any help please? thanks.

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• Quantifying the Performance of Garbage Collection vs. Explicit Memory Management

  - by EmbeddedProg

  I found this article here: Quantifying the Performance of Garbage Collection vs. Explicit Memory Management http://www.cs.umass.edu/~emery/pubs/gcvsmalloc.pdf In the conclusion section, it reads: Comparing runtime, space consumption, and virtual memory footprints over a range of benchmarks, we show that the runtime performance of the best-performing garbage collector is competitive with explicit memory management when given enough memory. In particular, when garbage collection has five times as much memory as required, its runtime performance matches or slightly exceeds that of explicit memory management. However, garbage collection’s performance degrades substantially when it must use smaller heaps. With three times as much memory, it runs 17% slower on average, and with twice as much memory, it runs 70% slower. Garbage collection also is more susceptible to paging when physical memory is scarce. In such conditions, all of the garbage collectors we examine here suffer order-of-magnitude performance penalties relative to explicit memory management. So, if my understanding is correct: if I have an app written in native C++ requiring 100 MB of memory, to achieve the same performance with a "managed" (i.e. garbage collector based) language (e.g. Java, C#), the app should require 5*100 MB = 500 MB? (And with 2*100 MB = 200 MB, the managed app would run 70% slower than the native app?) Do you know if current (i.e. latest Java VM's and .NET 4.0's) garbage collectors suffer the same problems described in the aforementioned article? Has the performance of modern garbage collectors improved? Thanks.

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• Inconsistent canvas drawing in Android browser

  - by user2943466

  In putting together a small canvas app I've stumbled across a weird behavior that only seems to occur in the default browser in Android. When drawing to a canvas that has the globalCompositeOperation set to 'destination-out' to act as the 'eraser' tool, Android browser sometimes acts as expected, sometimes does not update the pixels in the canvas at all. the setup: context.clearRect(0,0, canvas.width, canvas.height); context.drawImage(img, 0, 0, canvas.width, canvas.height); context.globalCompositeOperation = 'destination-out'; draw a circle to erase pixels from the canvas: context.fillStyle = '#FFFFFF'; context.beginPath(); context.arc(x,y,25,0,TWO_PI,true); context.fill(); context.closePath(); a small demo to illustrate the issue can be seen here: http://gumbojuice.com/files/source-out/ and the javascript is here: http://gumbojuice.com/files/source-out/js/main.js this has been tested in multiple desktop and mobile browsers and behaves as expected. On Android native browser after refreshing the page sometimes it works, sometimes nothing happens. I've seen other hacks that move the canvas by a pixel in order to force a redraw but this is not an ideal solution.. Thanks all.

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• Building html structure in php or javascript?

  - by Adam

  I've been doing a lot of ajax calls and using the returned data to build html with javascript. However, I've noticed some people are returning the constructed html in the ajax calls since they're doing it all in php. What is the preferred method? I have a bunch of stuff already using javascript, so I guess I would prefer not changing everything to use just php. But, I'm assuming php would be more "secure."? The following is what I've been doing: $main_frag = $("<div class='order-container'/>"); $contact_frag = $("<div class='group'><div class='line-data'>Name: "+data.name+"</div><div class='line-data'>Email: "+data.email+"</div><div class='line-data'>Phone: "+data.phone+"</div></div>"); $address_frag = $("<div class='group'><div class='line-data'>Address 1: "+data.address_one+"</div><div class='line-data'>Address 2: "+address2+"</div><div class='line-data'>City: "+data.city+"</div><div class='line-data'>Province: "+data.province+"</div><div class='line-data'>Postal Code: "+data.postal+"</div></div>"); etc.. I just want to hear the opinions of the community.

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• Jquery each function promblem.

  - by Cesar Lopez

  I have the following function: var emptyFields = false; function checkNotEmpty(tblName, columns, className){ emptyFields = false; $("."+className+"").each(function() { if($.trim($(this).val()) === "" &amp;&amp; $(this).is(":visible")){ emptyFields = true; return false; // break out of the each-loop } }); if (emptyFields) { alert("Please fill in current row before adding a new one.") } else { AddRow_OnButtonClick(tblName,columns); } } Its checking that all elements in the table are not empty before adding a new row, and I only need to check that the last row of the table has at least an element which its not empty and not the whole table. The className its applied to the table. Please notice, that the problem I have its checking the last row and only one element of the row has to have some text in it. (e.g. each row has 5 textboxes at least one textbox need to have some text inside in order to be able to add another row, otherwise, the alert comes up). Any help would be apreciated. Thanks

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• XSLT, process elements one by one

  - by qui

  Hi I am quite weak at XSLT so this might seem obvious. Here is some sample XML <term> <name>cholecystocolonic fistula</name> <definition>blah blah</definition> <reference>cholecystocolostomy</reference> </term> And here is the XSLT I wrote a while ago to process it <xsl:template name="term"> { "dictitle": "<xsl:value-of select="name" disable-output-escaping="yes" />", "html": "<xsl:value-of select="definition" disable-output-escaping="yes"/>", "referece": "<xsl:value-of select="reference" disable-output-escaping="yes"/> } </xsl:template> Basically I am creating JSON from the XML. The requirements have now changed so that now the XML can have more than one definition tag and reference tag. They can appear in any order, i.e definition, reference, reference, definition, reference. How can I update the XSLT to accommodate this? Probably worth mentioning that because my XSLT processor is using .NET I can only use XSLT 1.0 commands. Many thanks!

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• How do I get the earlist DateTime of a set, where there is a few conditions

  - by radbyx

  Create script for Product SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_PADDING ON GO CREATE TABLE [dbo].[Product]( [ProductID] [int] IDENTITY(1,1) NOT NULL, [ProductName] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO Create script for StateLog SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[StateLog]( [StateLogID] [int] IDENTITY(1,1) NOT NULL, [ProductID] [int] NOT NULL, [Status] [bit] NOT NULL, [TimeStamp] [datetime] NOT NULL, CONSTRAINT [PK_Uptime] PRIMARY KEY CLUSTERED ( [StateLogID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[StateLog] WITH CHECK ADD CONSTRAINT [FK_Uptime_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Product] ([ProductID]) GO ALTER TABLE [dbo].[StateLog] CHECK CONSTRAINT [FK_Uptime_Products] GO I have this and it's not enough: select top 5 [ProductName], [TimeStamp] from [Product] inner join StateLog on [Product].ProductID = [StateLog].ProductID where [Status] = 0 order by TimeStamp desc; (My query givess the 5 lastest TimeStamp's where Status is 0(false).) But I need a thing more: Where there is a set of lastest TimeStamps for a product where Status is 0, i only want the earlist of them (not the lastet). Example: Let's say for Product X i have: TimeStamp1(status = 0) TimeStamp2(status = 1) TimeStamp3(status = 0) TimeStamp4(status = 0) TimeStamp5(status = 1) TimeStamp6(status = 0) TimeStamp7(status = 0) TimeStamp8(status = 0) Correct answer would then be:: TimeStamp6, because it's the first of the lastest timestamps.

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• Please help!! Is there a better way to write this LINQ query

  - by Raj Aththanayake

  Hi Is there a better simplified way to write this query. My logic is if collection contains customer ids and countrycodes, do the query ordey by customer id ascending. If there are no contain id in CustIDs then do the order by customer name. Is there a better way to write this query? I'm not really familiar with complex lambdas. var custIdResult = (from Customer c in CustomerCollection where (c.CustomerID.ToLower().Contains(param.ToLower()) && (countryCodeFilters.Any(item => item.Equals(c.CountryCode))) ) select c).ToList(); if (custIdResult.Count > 0) { return from Customer c in custIdResult ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode)) ) orderby c.CustomerID ascending select c; } else { return from Customer c in CustomerCollection where ( c.CustomerName.ToLower().Contains(param.ToLower()) && countryCodeFilters.Any(item => item.Equals(c.CountryCode)) ) orderby c.CustomerName descending select c; }

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• Integration testing - can it be done right?

  - by Max

  I used TDD as a development style on some projects in the past two years, but I always get stuck on the same point: how can I test the integration of the various parts of my program? What I am currently doing is writing a testcase per class (this is my rule of thumb: a "unit" is a class, and each class has one or more testcases). I try to resolve dependencies by using mocks and stubs and this works really well as each class can be tested independently. After some coding, all important classes are tested. I then "wire" them together using an IoC container. And here I am stuck: How to test if the wiring was successfull and the objects interact the way I want? An example: Think of a web application. There is a controller class which takes an array of ids, uses a repository to fetch the records based on these ids and then iterates over the records and writes them as a string to an outfile. To make it simple, there would be three classes: Controller, Repository, OutfileWriter. Each of them is tested in isolation. What I would do in order to test the "real" application: making the http request (either manually or automated) with some ids from the database and then look in the filesystem if the file was written. Of course this process could be automated, but still: doesn´t that duplicate the test-logic? Is this what is called an "integration test"? In a book i recently read about Unit Testing it seemed to me that integration testing was more of an anti-pattern?

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• Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

  - by DanM

  I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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• Parsing XML with Ruby and Nokogiri

  - by Chip Castle

  I have the following XML structure: <charsets> <charset> <name>ANSI_X3.4-1968</name> <aliases> <alias>iso-ir-6</alias> <alias>ANSI_X3.4-1986</alias> <alias>ISO_646.irv:1991</alias> <alias>ASCII</alias> <alias>ISO646-US</alias> <alias>US-ASCII</alias> <alias>us</alias> <alias>IBM367</alias> <alias>cp367</alias> <alias>csASCII</alias> </aliases> </charset> <charset> <name>ISO-10646-UTF-1</name> <aliases> <alias>csISO10646UTF1</alias> </aliases> </charset> </charsets> I can grab the text contents of the the name nodes using Ruby and Nokogiri using: require 'nokogiri' require 'open-uri' doc = Nokogiri::XML(File.open("StandardCharsets.xml")) @charsets = doc.css("charsets name").map {|node| node.children.text } But, what I want is the text contents of all name and alias nodes in the order as they are shown in the source document. Everything I try fails. Does anyone have a good example of how to do this?

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• Issue with post data not received in a php page

  - by jul

  hi, I created a page in Wordpress (http://www.exam-vision.com/testmail) that sends POST data to itself in order to send an email. The code is shown below. While it seems that data are sent properly, it seems that they are not received since isset($_REQUEST['email']) is always false. Anybody could help? Thanks Jul <?php if (isset($_REQUEST['email'])) //if "email" is filled out, send email { //send email echo "isset email is true"; $email = $_REQUEST['email'] ; $subject = $_REQUEST['subject'] ; $message = $_REQUEST['message'] ; mail( "[email protected]", "Subject: $subject", $message, "From: $email" ); echo "Thank you for using our mail form"; } else //if "email" is not filled out, display the form { echo "<form method='post' action=''> Email: <input name='email' type='text' /><br /> Subject: <input name='subject' type='text' /><br /> Message:<br /> <textarea name='message' rows='15' cols='40'> </textarea><br /> <input type='submit' /> </form>"; } ?>

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• Effect.toggle and AJAX Calls

  - by kunalsawlani

  Hi, I am using the following code to capture all the AJAX calls being made from my app, in order to show a busy spinner till the call is completed. It works well when the requests are well spaced out. However, when the request are made in quick successions, some of the AJAX calls do not get registered, or the onCreate and onComplete actions get kicked off at the same time, and more often than not, the busy spinner continues to appear on the screen, after all the calls have successfully completed. Is there any check I can perform at the end of the call, to check if the element is visible, I can hide it. document.observe("dom:loaded", function() { $('loading').hide(); Ajax.Responders.register({ //When an Ajax call is made. onCreate: function() { new Effect.toggle('loading', 'appear'); new Effect.Opacity('display-area', { from: 1.0, to: 0.3, duration: 0.7 }); }, onComplete: function() { new Effect.toggle('loading', 'appear'); new Effect.Opacity('display-area', { from: 0.3, to: 1, duration: 0.7 }); } }); }); Thanks!

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• How to enforce that HTTP client uses conditional requests for updates?

  - by Day

  In a (proper RMM level 3) RESTful HTTP API, I want to enforce the fact that clients should make conditional requests when updating resources, in order to avoid the lost update problem. What would be an appropriate response to return to clients that incorrectly attempt unconditional PUT requests? I note that the (abandoned?) mod_atom returns a 405 Method Not Allowed with an Allow header set to GET, HEAD (view source) when an unconditional update is attempted. This seems slightly misleading - to me this implies that PUT is never a valid method to attempt on the resource. Perhaps the response just needs to have an entity body explaining that If-Match or If-Unmodified-Since must be used to make the PUT request conditional in which case it would be allowed? Or perhaps a 400 Bad Request with a suitable explanation in the entity body would be a better solution? But again, this doesn't feel quite right because it's using a 400 response for a violation of application specific semantics when RFC 2616 says (my emphasis): The request could not be understood by the server due to malformed syntax. But than again, I think that using 400 Bad Request for application specific semantics is becoming a widely accepted pragmatic solution (citation needed!), and I'm just being overly pedantic.

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• How do you send an extended-ascii AT-command (CCh) from Android bluetooth to a serial device?

  - by softex

  This one really has me banging my head. I'm sending alphanumeric data from an Android app, through the BluetoothChatService, to a serial bluetooth adaptor connected to the serial input of a radio transceiver. Everything works fine except when I try to configure the radio on-the-fly with its AT-commands. The AT+++ (enter command mode) is received OK, but the problem comes with the extended-ascii characters in the next two commands: Changing the radio destination address (which is what I'm trying to do) requires CCh 10h (plus 3 hex radio address bytes), and exiting the command mode requires CCh ATO. I know the radio can be configured OK because I've done it on an earlier prototype with the serial commands from PIC basic, and it also can be configured by entering the commands directly from hyperterm. Both these methods somehow convert that pesky CCh into a form the radio understands. I've have tried just about everything an Android noob could possibly come up with to finagle the encoding such as: private void command_address() { byte[] addrArray = {(byte) 0xCC, 16, 36, 65, 21, 13}; CharSequence addrvalues = EncodingUtils.getString(addrArray, "UTF-8"); sendMessage((String) addrvalues); } but no matter what, I can't seem to get that high-order byte (CCh/204/-52) to behave as it should. All other (< 127) bytes, command or data, transmit with no problem. Any help here would be greatly appreciated. -Dave

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• Java: How do I implement a method that takes 2 arrays and returns 2 arrays?

  - by HansDampf

  Okay, here is what I want to do: I want to implement a crossover method for arrays. It is supposed to take 2 arrays of same size and return two new arrays that are a kind of mix of the two input arrays. as in [a,a,a,a] [b,b,b,b] ------ [a,a,b,b] [b,b,a,a]. Now I wonder what would be the suggested way to do that in Java, since I cannot return more than one value. My ideas are: - returning a Collection(or array) containing both new arrays. I dont really like that one because it think would result in a harder to understand code. - avoiding the need to return two results by calling the method for each case but only getting one of the results each time. I dont like that one either, because there would be no natural order about which solution should be returned. This would need to be specified, though resulting in harder to understand code. Plus, this will work only for this basic case, but I will want to shuffle the array before the crossover and reverse that afterwards. I cannot do the shuffling isolated from the crossover since I wont want to actually do the operation, instead I want to use the information about the permutation while doing the crossover, which will be a more efficient way I think.

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• How do you send email from IMAP account with PHP?

  - by arthurakay

  I'm having an issue sending email via PHP/IMAP - and I don't know if it's because: I don't correctly understand IMAP, or there's an issue with my server My application opens an IMAP connection to an email account to read messages in the inbox. It does this successfully. The problem I have is that I want to send messages from this account and have them display in the outbox/sent folder. As far as I can tell, the PHP imap_mail() function doesn't in any way hook into the IMAP stream I currently have open. My code executes without throwing an error. However, the email never arrives to the recipient and never displays in my sent folder. private function createHeaders() { return "MIME-Version: 1.0" . "\r\n" . "Content-type: text/html; charset=iso-8859-1" . "\r\n" . "From: " . $this->accountEmail . "\r\n"; } private function notifyAdminForCompleteSet($urlToCompleteSet) { $message = " <p> In order to process the latest records, you must visit <a href='$urlToCompleteSet'>the website</a> and manually export the set. </p> "; try { imap_mail( $this->adminEmail, "Alert: Manual Export of Records Required", wordwrap($message, 70), $this->createHeaders() ); echo(" ---> Admin notified via email!\n"); } catch (Exception $e) { throw new Exception("Error in notifyAdminForCompleteSet()"); } } I'm guessing I need to copy the message into the IMAP account manually... or is there a different solution to this problem? Also, does it matter if the domain in the "from" address is different than that of the server on whicn this script is running? I can't explain why the message is never sent.

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• What's a good starting point, tutorial, or project, to learn database programming?

  - by DarthNoodles

  I've been a Software Developer now for over 10 years. I've mostly worked in Embedded C with some time spent on C++ (limited) and Java. I'm looking to learn some new technologies and skills. I thought that database programming may be interesting to learn. I would like to make my own pet project in order to learn these things. My platform of choice is Windows but can work in Linux also. My ideal pet project would involve a GUI and some network/internet programming also which I have some experience doing. I wouldn't mind getting into C# but don't want to bite off more than I can chew right now as my spare time is limited. If I understand correctly SQLite allows for programs to use a database without running an ODBC server. Is this correct? Is that a good place to start? What can I do to start that is not too complicated but not so simple that I won't learn the details also? Your opinions and feedback would be appreciated.

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• Quickly generate junk data of certain size in Javascript

  - by user1357607

  I am writing an upload speed test in Javascript. I am using Jquery (and Ajax) to send chunks of data to a server in order to time how long it takes to get a response. This should, in theory give an estimation, of the upload speed. Of course to cater for different bandwidths of the user I sequentially upload larger and larger amounts of junk data until a threshold duration is reached. Currently I generate the junk data using the following function, however, it is very slow when generation megabytes of data. function generate_random_data(size){ var chars = "abcdefghijklmnopqrstuvwxyz"; var random_data = ""; for (var i = 0; i < size; i++){ var random_num = Math.floor(Math.random() * char.length); random_data = random_data + chars.substring(random_num,random_num+1); } return random_data; Really all I am doing is generating a chunk of bytes to send to the server, however, this is the only way I could find out how in Javascript. Any help would be appreciated.

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• Java: multi-threaded maps: how do the implementations compare?

  - by user346629

  I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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• Python "callable" attribute (pseudo-property)

  - by mgilson

  In python, I can alter the state of an instance by directly assigning to attributes, or by making method calls which alter the state of the attributes: foo.thing = 'baz' or: foo.thing('baz') Is there a nice way to create a class which would accept both of the above forms which scales to large numbers of attributes that behave this way? (Shortly, I'll show an example of an implementation that I don't particularly like.) If you're thinking that this is a stupid API, let me know, but perhaps a more concrete example is in order. Say I have a Document class. Document could have an attribute title. However, title may want to have some state as well (font,fontsize,justification,...), but the average user might be happy enough just setting the title to a string and being done with it ... One way to accomplish this would be to: class Title(object): def __init__(self,text,font='times',size=12): self.text = text self.font = font self.size = size def __call__(self,*text,**kwargs): if(text): self.text = text[0] for k,v in kwargs.items(): setattr(self,k,v) def __str__(self): return '<title font={font}, size={size}>{text}</title>'.format(text=self.text,size=self.size,font=self.font) class Document(object): _special_attr = set(['title']) def __setattr__(self,k,v): if k in self._special_attr and hasattr(self,k): getattr(self,k)(v) else: object.__setattr__(self,k,v) def __init__(self,text="",title=""): self.title = Title(title) self.text = text def __str__(self): return str(self.title)+'<body>'+self.text+'</body>' Now I can use this as follows: doc = Document() doc.title = "Hello World" print (str(doc)) doc.title("Goodbye World",font="Helvetica") print (str(doc)) This implementation seems a little messy though (with __special_attr). Maybe that's because this is a messed up API. I'm not sure. Is there a better way to do this? Or did I leave the beaten path a little too far on this one? I realize I could use @property for this as well, but that wouldn't scale well at all if I had more than just one attribute which is to behave this way -- I'd need to write a getter and setter for each, yuck.

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• initalizing two pointers to same value in "for" loop

  - by MCP

  I'm working with a linked list and am trying to initalize two pointers equal to the "first"/"head" pointer. I'm trying to do this cleanly in a "for" loop. The point of all this being so that I can run two pointers through the linked list, one right behind the other (so that I can modify as needed)... Something like: //listHead = main pointer to the linked list for (blockT *front, *back = listHead; front != NULL; front = front->next) //...// back = back->next; The idea being I can increment front early so that it's one ahead, doing the work, and not incrementing "back" until the bottom of the code block in case I need to backup in order to modify the linked list... Regardless as to the "why" of this, in addition to the above I've tried: for (blockT *front = *back = listHead; /.../ for (blockT *front = listHead, blockT *back = listHead; /.../ I would like to avoid pointer to a pointer. Do I just need to initialize these before the loop? As always, thanks!

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• TCP/IP Implementation General Questions

  - by user2971023

  I've implemented the concepts shown here; http://wiki.unity3d.com/index.php/Simple_TCP/IP_Client_-_Server outside of unity and it works. (though i had to create the TCPIPServerApp from scratch as i could not find the base project anywhere). I have some general questions on how to use tcp/ip properly however. I've done some research on tcp/ip itself but I'm still a little confused. It seems like using the method above doesn't guarantee that I'll see the message (res). It just checks on every update to see if there is a different message in res. What if multiple messages are sent and the program lags or something, will i miss the earlier packet(s)? Should i instead do an array so it stores the last X messages? How do i know the data was received? Do I need to add a message id and build in my own ack into the data? Should i check to see if the port is in use before setting up a connection? Sorry for all the questions. This is all new to me but I enjoy this very much! ... Below already answered By Anton, Thanks It sounds like tcp uses its own packet numbering to ensure the packets end up in the right order on the other side. What if a packet is missed, are the subsequent packets thrown away? Or is this numbering and packet ordering, only for handling data that is broken out into multiple packets? TCP will automatically break the data into multiple packets if necessary right?

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