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• How to DRY on CRUD parts of my Rails app?

  - by kolrie

  I am writing an app which - similarly to many apps out there - is 90% regular CRUD things and 10% "juice", where we need nasty business logic and more flexibility and customization. Regarding this 90%, I was trying to stick to the DRY principle as much as I can. As long as controllers go, I have found resource_controller to really work, and I could get rid of all the controllers on that area, replacing them with a generic one. Now I'd like to know how to get the same with the views. On this app I have an overall, application.html.erb layout and then I must have another layout layer, common for all CRUD views and finally a "core" part: On index.html.erb all I need to generate a simple table with the fields and labels I indicate. For new and edit, also generic form edition, indicating labels and fields (with a possibility of providing custom fields if needed). I am not sure I will need show, but if I do it would be the same as new and edit. What plugins and tools (or even articles and general pointer) would help me to get that done? Thanks, Felipe.

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• Hash Code for a group of three fields

  - by Gauranga

  I have three fields namely Number1 Number2 Time I am trying to write a function in java that returns a unique hash value (long needs to be the return type of hash) for the above fields. This hash would then be used to store database rows corresponding to the above mentioned fields in a HashSet. I am new to writing a hash code function, can someone please review what I have. Any help would be appreciated. public class HashCode { private long Number1; private long Number2; String Time; public HashCode(long Number1, long Number2, String Time){ this.Number1 = Number1; this.Number2 = Number2; this.Time = Time; } public long getHashCode() { long hash = 3; hash = 47 * hash + (long) (this.Number1 ^ (this.Number1 >>> 32)); hash = 47 * hash + (long) (this.Number2 ^ (this.Number2 >>> 32)); hash = 47 * hash + (this.Time != null ? this.Time.hashCode() : 0); return hash; } }

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• My python program always brings down my internet connection after several hours running, how do I debug and fix this problem?

  - by Shane

  I'm writing a python script checking/monitoring several server/websites status(response time and similar stuff), it's a GUI program and I use separate thread to check different server/website, and the basic structure of each thread is using an infinite while loop to request that site every random time period(15 to 30 seconds), once there's changes in website/server each thread will start a new thread to do a thorough check(requesting more pages and similar stuff). The problem is, my internet connection always got blocked/jammed/messed up after several hours running of this script, the situation is, from my script side I got urlopen error timed out each time it's requesting a page, and from my FireFox browser side I cannot open any site. But the weird thing is, the moment I close my script my Internet connection got back on immediately which means now I can surf any site through my browser, so it must be the script causing all the problem. I've checked the program carefully and even use del to delete any connection once it's used, still get the same problem. I only use urllib2, urllib, mechanize to do network requests. Anybody knows why such thing happens? How do I debug this problem? Is there a tool or something to check my network status once such situation occurs? It's really bugging me for a while... By the way I'm behind a VPN, does it have something to do with this problem? Although I don't think so because my network always get back on once the script closed, and the VPN connection never drops(as it appears) during the whole process.

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• Oracle Forms on-button-pressed trigger to solve three scenarios

  - by DBase486

  Hello, I'm writing a when-button-pressed trigger on a save button for an Oracle Forms 6i form, and it has to fulfill a couple of scenarios. Here's some background information: the fields we're primarily concerned with are: n_number, alert_id, end_date For all three scenarios we are comparing candidate records against the following records in the database (for the sake of argument, let's assume they're the only records in the database so far): alert_id|| n_number|| end_date ------------------------------------- 1|| 5|| _______ 2|| 6|| 10/25/2009 Scenario 1: The user enters a new record: alert_id 1 n_number 5 end_date NULL Objective: prevent the user from committing duplicate rows Scenario 2: The user enters a new record: alert_id 1 n_number 10 end_date NULL Objective: Notify the user that this alert_id already exists, but allow the user the ability to commit the row, if desired. Scenario 3: The user enters a new record: alert_id 2 n_number 6 end_date NULL Objective: Notify the user that this alert_id has occurred in the past (i.e. it has a not-null end_date), but allow the user to commit the row, if desired. I've written the code, which seems to comply with the first two scenarios, but prevents me from fulfilling the third. Issues: When I enter the third scenario case, I am prompted to commit the record, but when I attempt this, the "duplicate_stop" alert pops up, preventing me. Issues: I'm getting the following error: ORA-01843: not a valid month. While testing the code for the third scenario in Toad (hard-coding the values, etc) things seemed to be fine. Why would I encounter these problems at run-time? Help is very much appreciated. Thank you

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• Regex expression is too greedy

  - by alastairs

  I'm writing a regular expression to match data from the IMDb soundtracks data file. My regexes are mostly working, although they are in places slurping too much text into my named groups. Take the following regex for example: "^ Performed by '?(?<performer>.*)('? \(qv\))?$" The performer group includes the string ' (qv) as well as the performer's name. Unfortunately, because the records are not consistently formatted, some performers' names are surrounded by single quotation marks whilst others are not. This means they are optional as far as the regex is concerned. I've tried marking the last group as a greedy group using the ?> group specifier, but this appeared to have no effect on the results. I can improve the results by changing the performer group to match a small range of characters, but this reduces my chances of parsing the name out correctly. Furthermore, if I were to just exclude the apostrophe character, I would then be unable to parse, e.g., band names containing apostrophes, such as Elia's Lonely Friends Band who performed Run For Your Life featured in Resident Evil: Apocalypse.

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• Avoid an "out of memory error" in Java(eclipse), when using large data structure?

  - by gnomed

  OK, so I am writing a program that unfortunately needs to use a huge data structure to complete its work, but it is failing with a "out of memory error" during its initialization. While I understand entirely what that means and why it is a problem, I am having trouble overcoming it, since my program needs to use this large structure and I don't know any other way to store it. The program first indexes a large corpus of text files that I provide. This works fine. Then it uses this index to initialize a large 2D array. This array will have nXn entries, where "n" is the number of unique words in the corpus of text. For the relatively small chunk I am testing it on(about 60 files) it needs to make approximately 30,000x30,000 entries. this will probably be bigger once I run it on my full intended corpus too. It consistently fails every time, after it indexes, while it is initializing the data structure(to be worked on later). Things I have done include: revamp my code to use a primitive "int[]" instead of a "TreeMap" eliminate redundant structures, etc... Also, I have run eclipse with "eclipse -vmargs -Xmx2g" to max out my allocated memory I am fairly confident this is not going to be a simple line of code solution, but is most likely going to require a very new approach. I am looking for what that approach is, any ideas? Thanks, B.

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• Why does mobile first responsive design tend to not use max-width queries alongside the min-width queries?

  - by Sam

  First off, I understand the basic principles behind mobile first responsive web design, and totally agree with them. But one thing I don't understand: In my experience, not all styles for small screens can be used for the larger version of a website. For example, usually smaller versions tend to have larger clickable areas, hamburger navigation, etc. So I sometimes have to override these specific styles, aside from just progressively enhancing the base styles. So I was wondering: why is max-width rarely mentioned (or used) in the context of mobile-first responsive web design? Because it looks like it could be used to isolate styles for smaller screens that are not useful for larger screens, and would thus prevent unnecessary duplication of code. A quote which mentions min-width as typically mobile-first, but not max-width: Mobile first, from a coding perspective, means that your base style is typically a single-column, fully-fluid layout. You use @media (min-width: whatever) to add a grid-based layout on top of that. from: http://gomakethings.com/mobile-first-and-internet-explorer/ EDIT: So to be more specific: I was wondering if there is a reason to exclude max-width from a mobile-first responsive design (as it seems like it can be useful for writing your css as DRY as possible, as some styles for small screens will not be used for bigger screens).

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• transmit a java.lang.reflect.Proxy over a network

  - by panzi

  Is there a convenient way to transmit an object including its code (the class) over a network (not just the instance data)? Don't ask me why I want to do this. It's in an assignment. I asked several times if that is really what they meant and the didn't rephrase their answer so I guess they really want us to transmit code (not just the field data) over a network. To be honest I have no clue why we need a Proxy in this assignment anyway, just writing a simple class would do IMO. The assignment says that we should instantiate the proxy on the server and transmit it to the client (and yes, they talk about a java.lang.reflect.Proxy, they name this class). Because there is no class file for a proxy I can't deploy that. I guess I would have to somehow read out the bytecode of the generated Proxy, transmit it to the client and then load it. Which makes absolutely no sense at all, but this seems what they want us to do. I don't get why.

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• jQuery: Stopping a periodic ajax call?

  - by Legend

  I am writing a small jQuery plugin to update a set of Divs with content obtained using Ajax calls. Initially, let's assume we have 4 divs. I am doing something like this: (function($) { .... .... //main function $.fn.jDIV = { init: function() { ... ... for(var i = 0; i < numDivs; i++) { this.query(i); } this.handlers(); }, query: function(divNum) { //Makes the relevant ajax call }, handlers: function() { for(var i = 0; i < numDivs; i++) { setInterval("$.fn.jDIV.query(" + i + ")", 5000); } } }; })(jQuery); I would like to be able to enable and disable a particular ajax query. I was thinking of adding a "start" and "stop" instead of the "handlers" function and subsequently storing the setInterval handler like this: start: function(divNum) { divs[divNum] = setInterval("$.fn.jDIV.query(" + i + ")", 5000); }, stop: function(divNum) { clearInterval(divs[divNum]); } I did not use jQuery to setup and destroy the event handlers. Is there a better approach (perhaps using more of jQuery) to achieve this?

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• If I use Unicode on a ISO-8859-1 site, how will that be interpreted by a browser?

  - by grg-n-sox

  So I got a site that uses ISO-8859-1 encoding and I can't change that. I want to be sure that the content I enter into the web app on the site gets parsed correctly. The parser works on a character by character basis. I also cannot change the parser, I am just writing files for it to handle. The content in my file I am telling the app to display after parsing contains Unicode characters (or at least I assume so, even if they were produced by Windows Alt Codes mapped to CP437). Using entities is not an option due to the character by character operation of the parser. The only characters that the parser escapes upon output are markup sensitive ones like ampersand, less than, and greater than symbols. I would just go ahead and put this through to see what it looks like, but output can only be seen on a publishing, which has to spend a couple days getting approved and such, and that would be asking too much for just a test case. So, long story short, if I told a site to output ?ÇÑ¥?? on a site with a meta tag stating it is supposed to use ISO-8859-1, will a browser auto-detect the Unicode and display it or will it literally translate it as ISO-8859-1 and get a different set of characters?

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• PHP question about global variables and form requests

  - by user220201

  Hi, This is probably a stupid question but will ask anyway sine I have no idea. I have written basic php code which serve forms. Say I have a login page and I serve it using the login.php page and it will be called in the login.html page like this - <form action="login.php" method="post"> By this it is also implied that every POST needs its own php file, doesn't it? This kind of feels weird. Is there a way to have a single file, say code.php, and just have each of the forms as functions instead? EDIT: Specifically, say I have 5 forms that are used one after the other in my application. Say after login the user does A, B, C and D tasks each of which are sent to the server as a POST request. So instead of having A.php, B.php, C.php and D.php I would like to have a single code.php and have A(), B(), C() and D() as functions. Is there a way to do this? Also on the same note, how do I deal with say a global array (e.g. an array of currently logged in users) across multiple forms? I want to do this without writing to a DB. I know its probably better to write to a DB and query but is it even possible to do it with a global array? The reason I was thinking about having all the form functions in one file is to use a global array. Thanks, - Pav

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• In what order should the Python concepts be explained to absolute beginners?

  - by Tomaž Pisanski

  I am teaching Python to undergraduate math majors. I am interested in the optimal order in which students should be introduced to various Python concepts. In my view, at each stage the students should be able to solve a non-trivial programming problem using only the tools available at that time. Each new tool should enable a simpler solution to a familiar problem. A selection of numerous concepts available in Python is essential in order to keep students focused. They should also motivated and should appreciate each newly mastered tool without too much memorization. Here are some specific questions: For instance, my predecessor introduced lists before strings. I think the opposite is a better solution. Should function definitions be introduced at the very beginning or after mastering basic structured programming ideas, such as decisions (if) and loops (while)? Should sets be introduced before dictionaries? Is it better to introduce reading and writing files early in the course or should one use input and print for most of the course? Any suggestions with explanations are most welcome.

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• Does Microsoft Access use the PK fields for anything?

  - by chrismay

  Ok this is going to sound strange, but I have inherited an app that is an Access front end with a SQL Server backend. I am in the process of writing a new front end for it, but... we need to continue using the access front end for a while even after we deploy my new front end for reasons I won't go into. So both the existing Access app and my new app will need to be able to access and work with the data. The problem is the database design is a nightmare. For example some simple parent-child table relationships have like 4 and 5 part composite primary keys. I would REALLY like to remove these PKs and replace them with unique constraints or whatever, and add a new column to each of these tables called ID that is just an identity. If I change the PK and FKs on these tables to more managable fields, will the Access app have problems? What I mean is, does access use the meta data from the tables (PK and FK info) in such a way that it would break the app to change these?

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• How can I control UISlider Value Changed-events frequncy?

  - by Albert

  I'm writing an iPhone app that is using two uisliders to control values that are sent using coreBluetooth. If I move the sliders quickly one value freezes at the receiver, presumably because the Value Changed events trigger so often that the write-commands stack up and eventually get thrown away. How can I make sure the events don't trigger too often? Edit: Here is a clarification of the problem; the bluetooth connection sends commands every 105ms. If the user generates a bunch of events during that time they seem to que up. I would like to throw away any values generated between the connection events and just send one every 105ms. This is basically what I'm doing right now: -(IBAction) sliderChanged:(UISlider *)sender{ static int8_t value = 0; int8_t new_value = (int8_t)sender.value; if ( new_value > value + threshold || new_value < value - threshold ) { value = new_value; [btDevice writeValue:value]; } } What I'm asking is how to implement something like -(IBAction) sliderChanged:(UISlider *)sender{ static int8_t value = 0; if (105msHasPassed) { int8_t new_value = (int8_t)sender.value; if ( new_value > value + threshold || new_value < value - threshold ) { value = new_value; [btDevice writeValue:value]; } } }

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• Use properties or methods to expose business rules in C#?

  - by Val

  I'm writing a class to encapsulate some business rules, each of which is represented by a boolean value. The class will be used in processing an InfoPath form, so the rules get the current program state by looking up values in a global XML data structure using XPath operations. What's the best (most idiomatic) way to expose these rules to callers -- properties or public methods? Call using properties Rules rules = new Rules(); if ( rules.ProjectRequiresApproval ) { // get approval } else { // skip approval } Call using methods Rules rules = new Rules(); if ( rules.ProjectRequiresApproval() ) { // get approval } else { // skip approval } Rules class exposing rules as properties public class Rules() { private int _amount; private int threshold = 100; public Rules() { _amount = someExpensiveXpathOperation; } // rule property public bool ProjectRequiresApproval { get { return _amount < threshold } } } Rules class exposing rules as methods public class Rules() { private int _amount; private int threshold = 100; public Rules() { _amount = someExpensiveXpathOperation; } // rule method public bool ProjectRequiresApproval() { return _amount < threshold; } } What are the pros and cons of one over the other?

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• Am I using the getch() function from the ncurses library incorrectly?

  - by user1692446

  I am writing a Pacman game in c++ using the ncurses library, but I am not able to move the Pacman properly. I have used getch() to move it it up, down, left and right, but it only moves right and does not move anywhere else when I press any other key. This is a code snippet for moving up. I have written similar code with some conditions altered accordingly for moving left, right and down. int ch = getch(); if (ch == KEY_RIGHT) { int i,row,column; //getting position of cursor by getyx function for (i=column; i<=last_column; i+=2) { //time interval of 1 sec mvprintw(row,b,"<"); //print < in given (b,row) coordinates //time interval of 1 sec mvprintw(row,(b+1),"O"); //print "O" next to "<" int h = getch(); //to give the option for pressing another key if (h != KEY_RIGHT) //break current loop if another key is pressed { break; } } } if (condition) { //code to move left } Am I using getch() wrong, or is there something else I have to do?

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• How to make ActiveRecord work with legacy partitioned/sharded databases/tables?

  - by Utensil

  thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate),I figure that I have to describe the specific problem I met and ask around. My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below: way database and table name shard by (maybe it's should be called partitioned by?) YZ.X db_YZ.tb_X order serial number last three digits YYYYMMDD. db_YYYYMMDD.tb date YYYYMM.DD db_YYYYMM.tb_ DD date too The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution. I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most. But this is just not DRY! What I need is a clean solution like the following DSL: class Order < ActiveRecord::Base shard_by :order_serialno do |key| [get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const get_db_name_by(key), get_tb_name_by(key), ] end end Can anybody enlight me? Any help would be greatly appreciated~~~~

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• Is Assert.Fail() considered bad practice?

  - by Mendelt

  I use Assert.Fail a lot when doing TDD. I'm usually working on one test at a time but when I get ideas for things I want to implement later I quickly write an empty test where the name of the test method indicates what I want to implement as sort of a todo-list. To make sure I don't forget I put an Assert.Fail() in the body. When trying out xUnit.Net I found they hadn't implemented Assert.Fail. Of course you can always Assert.IsTrue(false) but this doesn't communicate my intention as well. I got the impression Assert.Fail wasn't implemented on purpose. Is this considered bad practice? If so why? @Martin Meredith That's not exactly what I do. I do write a test first and then implement code to make it work. Usually I think of several tests at once. Or I think about a test to write when I'm working on something else. That's when I write an empty failing test to remember. By the time I get to writing the test I neatly work test-first. @Jimmeh That looks like a good idea. Ignored tests don't fail but they still show up in a separate list. Have to try that out. @Matt Howells Great Idea. NotImplementedException communicates intention better than assert.Fail() in this case @Mitch Wheat That's what I was looking for. It seems it was left out to prevent it being abused in another way I abuse it.

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• How can I write an XML on my hard drive to GetRequestStream

  - by swolff1978

  I need to post raw xml to a site and read the response. With the following code I keep getting an "Unknown File Format" error and I'm not sure why. XmlDocument sampleRequest = new XmlDocument(); sampleRequest.Load(@"C:\SampleRequest.xml"); byte[] bytes = Encoding.UTF8.GetBytes(sampleRequest.ToString()); string uri = "https://www.sample-gateway.com/gw.aspx"; req = WebRequest.Create(uri); req.Method = "POST"; req.ContentLength = bytes.Length; req.ContentType = "text/xml"; using (var requestStream = req.GetRequestStream()) { requestStream.Write(bytes, 0, bytes.Length); } // Send the data to the webserver rsp = req.GetResponse(); XmlDocument responseXML = new XmlDocument(); using (var responseStream = rsp.GetResponseStream()) { responseXML.Load(responseStream); } I am fairly certain my issue is what/how I am writing to the requestStream so.. How can I modify that code so that I may write an xml located on the hard drive to the request stream?

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• Syncing two AS3 NetStreams

  - by Lowgain

  I'm writing an app that requires an audio stream to be recording while a backing track is played. I have this working, but there is an inconsistent gap in between playback and record starting. I don't know if I can do anything to make the sync perfect every time, so I've been trying to track what time each stream starts so I can calculate the delay and trim it server-side. This also has proved to be a challenge as no events seem to be sent when a connection starts (as far as I know). I've tried using various properties like the streams' buffer sizes, etc. I'm thinking now that as my recorded audio is only mono, I may be able to put some kind of 'control signal' on the second stereo track which I could use to determine exactly when a sound starts recording (or stick the whole backing track in that channel so I can sync them that way). This leaves me with the new problem of properly injecting this sound into the NetStream. If anyone has any idea whether or not any of these ideas will work, how to execute them, or some alternatives, that would be extremely helpful! Been working on this issue for awhile

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• Evaluating expressions using Visual Studio 2005 SDK rather than automation's Debugger::GetExpression

  - by brone

  I'm looking into writing an addin (or package, if necessary) for Visual Studio 2005 that needs watch window type functionality -- evaluation of expressions and examination of the types. The automation facilities provide Debugger::GetExpression, which is useful enough, but the information provided is a bit crude. From looking through the docs, it sounds like an IDebugExpressionContext2 would be more useful. With one of these it looks as if I can get more information from an expression -- detailed information about the type and any members and so on and so forth, without having everything come through as strings. I can't find any way of actually getting a IDebugExpressionContext2, though! IDebugProgramProvider2 sort of looks relevant, in that I could start with IDebugProgramProvider2::GetProviderProcessData and then slowly drill down until reaching something that can supply my expression context -- but I'll need to supply a port to this, and it's not clear how to retrieve the port corresponding to the current debug session. (Even if I tried every port, it's not obvious how to tell which port is the right one...) I'm becoming suspicious that this simply isn't a supported use case, but with any luck I've simply missed something crashingly obvious. Can anybody help?

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• Should conditional expressions go inside or outside of classes?

  - by Rupert

  It seems that often I will want to execute some methods from a Class when I call it and choosing which function will depend on some condition. This leads me to write classes like in Case 1 because it allows me to rapidly include their functionality. The alternative would be Case 2 which can take a lot of time if there is a lot of code and also means more code being written twice when I drop the Class into different pages. Having said that, Case 1 feels very wrong for some reason that I can't quite put my finger on. I haven't really seen any classes written like this, I suppose. Is there anything wrong with writing classes like in Case 1 or is Case 2 superior? Or is there a better way? What the advantages and disadvantages of each? Case 1 class Foo { public function __construct($bar) { if($bar = 'action1') $this->method1(); else if($bar = 'action2') $this->method2(); else $this->method1(); } public function method1() { } public function method2() { } } $bar = 'action1' $foo = new Foo($bar); Case 2 class Foo { public function __construct() { } public function method1() { } public function method2() { } } $foo = new Foo; $bar = 'action1'; if($bar == 'action1') $foo->method1(); else if($bar == 'action2') $foo->method2(); else $foo->method1();

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• How do I bind to a custom view in Cocoa using Xcode 4?

  - by Newt

  I'm a beginner when it comes to writing Mac apps and working with Cocoa, so please forgive my ignorance. I'm looking to create a custom view, that exposes some properties, which I can then bind to an NSObjectController. Since it's a custom view, the Bindings Inspector obviously doesn't list any of the properties I've added to the view that I can then bind to using Interface Builder. After turning to the Stackoverflow/Google for help, I've stumbled across a couple of possible solutions, but neither seem to be quite right for my situation. The first suggested creating an IBPlugin, which would then mean my bindings would be available in the Bindings Inspector. I could then bind the view to the controller using IB. Apparently IBPlugins aren't supported in Xcode 4, so that one's out the window. I'm also assuming (maybe wrongly) that IBPlugins are no longer supported because there's a better way of doing such things these days? The second option was to bind the controller to the view programmatically. I'm a bit confused as to exactly how I would achieve this. Would it require subclassing NSObjectController so I can add the calls to bind to the view? Would I need to add anything to the view to support this? Some examples I've seen say you'd need to override the bind method, and others say you don't. Also, I've noticed that some example custom views call [self exposeBinding:@"bindingName"] in the initializer. From what I gather from various sources, this is something that's related to IBPlugins and isn't something I need to do if I'm not using them. Is that correct? I've found a post on Stackoverflow here which seems to discuss something very similar to my problem, but there wasn't any clear winner as to the best answer. The last comment by noa on 12th Sept seems interesting, although they mention you should be calling exposeBinding:. Is this comment along the right track? Is the call to exposeBinding really necessary? Apologies for any dumb questions. Any help greatly appreciated.

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• Omit return type in C++0x

  - by Clinton

  I've recently found myself using the following macro with gcc 4.5 in C++0x mode: #define RETURN(x) -> decltype(x) { return x; } And writing functions like this: template <class T> auto f(T&& x) RETURN (( g(h(std::forward<T>(x))) )) I've been doing this to avoid the inconvenience having to effectively write the function body twice, and having keep changes in the body and the return type in sync (which in my opinion is a disaster waiting to happen). The problem is that this technique only works on one line functions. So when I have something like this (convoluted example): template <class T> auto f(T&& x) -> ... { auto y1 = f(x); auto y2 = h(y1, g1(x)); auto y3 = h(y1, g2(x)); if (y1) { ++y3; } return h2(y2, y3); } Then I have to put something horrible in the return type. Furthermore, whenever I update the function, I'll need to change the return type, and if I don't change it correctly, I'll get a compile error if I'm lucky, or a runtime bug in the worse case. Having to copy and paste changes to two locations and keep them in sync I feel is not good practice. And I can't think of a situation where I'd want an implicit cast on return instead of an explicit cast. Surely there is a way to ask the compiler to deduce this information. What is the point of the compiler keeping it a secret? I thought C++0x was designed so such duplication would not be required.

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• Efficient way to maintain a sorted list of access counts in Python

  - by David

  Let's say I have a list of objects. (All together now: "I have a list of objects.") In the web application I'm writing, each time a request comes in, I pick out up to one of these objects according to unspecified criteria and use it to handle the request. Basically like this: def handle_request(req): for h in handlers: if h.handles(req): return h return None Assuming the order of the objects in the list is unimportant, I can cut down on unnecessary iterations by keeping the list sorted such that the most frequently used (or perhaps most recently used) objects are at the front. I know this isn't something to be concerned about - it'll make only a miniscule, undetectable difference in the app's execution time - but debugging the rest of the code is driving me crazy and I need a distraction :) so I'm asking out of curiosity: what is the most efficient way to maintain the list in sorted order, descending, by the number of times each handler is chosen? The obvious solution is to make handlers a list of (count, handler) pairs, and each time a handler is chosen, increment the count and resort the list. def handle_request(req): for h in handlers[:]: if h[1].handles(req): h[0] += 1 handlers.sort(reverse=True) return h[1] return None But since there's only ever going to be at most one element out of order, and I know which one it is, it seems like some sort of optimization should be possible. Is there something in the standard library, perhaps, that is especially well-suited to this task? Or some other data structure? (Even if it's not implemented in Python) Or should/could I be doing something completely different?

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