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  • Mono Develop 2.4.1 + linq error.

    - by Nev_Rahd
    I just started to learn Mono Develop Installed Mono Develop 2.4.1 and trial version of Mono Touch. my Code: using System; using System.Xml.Linq; using System.Collections.Generic; namespace RSSReader { public static class RSSRepository { public static IList<FeedItem> GetFeeds(string url) { XDocument rssFeed = XDocument.Load(url); Console.Write(rssFeed.ToString()); var feeds = new List<FeedItem>(); try { var query = from item in rssFeed.Descendants("item") select new FeedItem { Title = item.Element("title").Value, Published = DateTime.Parse(item.Element("pubDate").Value), Url = item.Element("link").Value }; feeds = query.ToList(); } catch (Exception ex){ Console.WriteLine(ex.Message); } return feeds; } } } This is throwing an error: An implementation of 'select' query expression pattern could not be found. Are you missing 'System.linq' using directive or 'System.Core.dll' assembly reference? I got both references to System.Xml.Linq and System.Core What am i missing ?

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  • JavaScript Keycode 46 is DEL Function key or (.) period sign?

    - by Omar
    Im writing some logic in JavaScript using jquery, where i must check the input content against a REGEX pattern ex: "^[a-zA-Z0-9_]*$" //Alpha-numeric and _ The logic is almost done, i just have a little problem filtering the function key DEL, my logic goes like this: var FunctionsKey = new Array(8, 9, 13, 16, 35, 36, 37, 39, 46); function keypressValidation(key) { if (config.regexExp != null) { if ($.inArray(key, FunctionsKey) != -1) { return true; } else { var keyChar = String.fromCharCode(key); return RegexCheck(keyChar); } } return true; } If the KeyCode is one of those in the array, i let it pass, if not i get the char and compare it against the REGEX. The problem is: in some Browsers the DEL and '.' (period sign) have the same key Code 46. So is there a better logic to filter the function keys or must i write a condition for that case, maybe removing the 46 from the array and try to convert it to char and if is (.) let it go to the Regex function if not let it pass? The other question will be are there more shared Key Codes in some browsers? EDIT: My suggested solution wont work because it doesn't matter which key the user pressed (DEL or period) i always get (.) as CHAR at least on OPERA and FF =(.

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  • Dimension Reduction in Categorical Data with missing values

    - by user227290
    I have a regression model in which the dependent variable is continuous but ninety percent of the independent variables are categorical(both ordered and unordered) and around thirty percent of the records have missing values(to make matters worse they are missing randomly without any pattern, that is, more that forty five percent of the data hava at least one missing value). There is no a priori theory to choose the specification of the model so one of the key tasks is dimension reduction before running the regression. While I am aware of several methods for dimension reduction for continuous variables I am not aware of a similar statical literature for categorical data (except, perhaps, as a part of correspondence analysis which is basically a variation of principal component analysis on frequency table). Let me also add that the dataset is of moderate size 500000 observations with 200 variables. I have two questions. Is there a good statistical reference out there for dimension reduction for categorical data along with robust imputation (I think the first issue is imputation and then dimension reduction)? This is linked to implementation of above problem. I have used R extensively earlier and tend to use transcan and impute function heavily for continuous variables and use a variation of tree method to impute categorical values. I have a working knowledge of Python so if something is nice out there for this purpose then I will use it. Any implementation pointers in python or R will be of great help. Thank you.

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  • Who needs singletons?

    - by sexyprout
    Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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  • Localisable Resources: how can (should one?!) wrap a UI layer source as a BL layer service?

    - by Ciel
    A service that returns localised strings could be wrapped in a service, so that it could be used both locally (eg in an MVC app) and remotely (eg possibly Silverlight). But...if sticking with the standard practice of creating resources in the UI assembly, that would in effect make a lower layer (BL/Services) have to have a ref on a higher layer (UI)...a definite no-no. And whereas a lot of AppWide resources (eg: AppName, OK, Cancel, etc.) could be defined in a Common cross-cutting assembly, and the BL/ResourceSerouce could ref and wrap those, that doesn't work in a a Modular App, where the Core app should have no binding to/knowledge of any Module. One solution could be to have each module, once mounted in mem, 'register' their Resource files with the service, who would then return it to the service (rather a long round trip, but at least consistent as a service, and potentially resources/images could be shared with other resources). Secondly, that may work in a web app...but not sure how that pattern could be extended to a Silverlight modular app (the round tripping becomes prohibitive). ie...what are best practices for allowing Resources to be to be defined by the UI designer, in a higher level, but served from the lower BL layer, as a Service? Or is there a better way of understanding/solving the problem?

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  • ForEach loop in Mathematica.

    - by dreeves
    I'd like something like this: ForEach[i_, {1,2,3}, Print[i] ] Or, more generally, to destructure arbitrary stuff in the list you're looping over, like: ForEach[{i_, j_}, {{1,10}, {2,20}, {3,30}}, Print[i*j] ] (Meta-question: is that a good way to call a ForEach loop, with the first argument a pattern like that?) ADDED: Some answerers have rightly pointed out that usually you want to use Map or other purely functional constructs and eschew a non-functional programming style where you use side effects. I agree! But here's an example where I think this ForEach construct is supremely useful: Say I have a list of options (rules) that pair symbols with expressions, like attrVals = {a -> 7, b -> 8, c -> 9} Now I want to make a hash table where I do the obvious mapping of those symbols to those numbers. I don't think there's a cleaner way to do that than ForEach[a_ -> v_, attrVals, h[a] = v] ADDED: I just realized that to do ForEach properly, it should support Break[] and Continue[]. I'm not sure how to implement that. Perhaps it will need to somehow be implemented in terms of For, While, or Do since those are the only loop constructs that support Break[] and Continue[]. If anyone interested in this wants to ask about that as a separate question, please do!

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  • Can FFT length affect filtering accuracy?

    - by Charles
    Hi, I am designing a fractional delay filter, and my lagrange coefficient of order 5 h(n) have 6 taps in time domain. I have tested to convolute the h(n) with x(n) which is 5000 sampled signal using matlab, and the result seems ok. When I tried to use FFT and IFFT method, the output is totally wrong. Actually my FFT is computed with 8192 data in frequency domain, which is the nearest power of 2 for 5000 signal sample. For the IFFT portion, I convert back the 8192 frequency domain data back to 5000 length data in time domain. So, the problem is, why this thing works in convolution, but not in FFT multiplication. Does converting my 6 taps h(n) to 8192 taps in frequency domain causes this problem? Actually I have tried using overlap-save method, which perform the FFT and multiplication with smaller chunks of x(n) and doing it 5 times separately. The result seems slight better than the previous, and at least I can see the waveform pattern, but still slightly distorted. So, any idea where goes wrong, and what is the solution. Thank you.

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  • LINQ to XML: suppressing redundant namespace attribute in child nodes

    - by GSerg
    If a node belongs to a namespace, it's children by default belong to the same namespace. So there's no need to provide an xmlns attribute on each child, which is good. However. If I create two nodes like this: Dim parent = <parent xmlns="http://my.namespace.org"/> Dim child = <child xmlns="http://my.namespace.org">value</child> parent.Add(child) Console.WriteLine(parent.ToString) The result is this: <parent xmlns="http://my.namespace.org"> <child xmlns="http://my.namespace.org">value</child> </parent> But, if create them in a less convenient way: Dim parent = <parent xmlns="http://my.namespace.org"/> Dim child As New XElement(XName.Get("child", "http://my.namespace.org")) With {.Value = "value"} parent.Add(child) Console.WriteLine(parent.ToString) The result is more desirable: <parent xmlns="http://my.namespace.org"> <child>value</child> </parent> Obviously, I'd prefer to use the first way because it is so much more intuitive and easy to code. There's also another reason to not use method 2 -- sometimes I need to create nodes with XElement.Parse, parsing a string that contains an xmlns attribute, which produces exactly same results as method 1. So the question is -- how do I get the pretty output of method 2, creating nodes as in method 1? The only option I see is to create a method that would clone given XElement, effectively recreating it according to method 2 pattern, but that seems ugly. I'm looking for a more obvious solution I overlooked for some reason.

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  • Can we solve the table row background image problem, in chrome, in multi celled tables??

    - by Ya'el
    It is frequently asked – but I haven’t seen a good answer yet (and I looked). If you set a background image in CSS to a table row- the image will repeat itself in every cell. If you set the position: relative (for the row) and set the background-image: none (for the cells) it solves the problem on IE but not on chrome! I can't use background positioning since there are many calls and their size varies. (And the picture is not symmetrical- It's a fade out from one side. Anybody?? Example for the css code : tr { height: 30px; position:relative;} tr.green {background: url('green_30.png') no-repeat left top;} tr.orange {background: url('oranger_30.png') no-repeat left top;} tr.red {background: url('red_30.png') no-repeat left top;} td {background-image:none;} The HTML is basic - A multi cell table. The goal is to have different colors fade into every row, but it could be any non-pattern image.

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  • How to best manage multi-frame MovieClips with classes?

    - by Arms
    After switching to AS3, I've been having a hell of a time figuring out the best way to manage MovieClips that have UI elements spread across multiple frames with a single class. An example that I am working on now is a simple email form. I have a MovieClip with two frames: the 1st frame has the form elements (text inputs, submit button) the 2nd frame has a "thank you" message and a button to go back to the first frame (to send another email) In the library I have linked the MovieClip to a custom class (Emailer). My immediate problem is how do I assign a MouseEvent.CLICK event to the button on the 2nd frame? I should note at this point that I am trying to avoid putting code on the timeline (except for stop() calls). This is how I am 'solving' the problem now: Emailer registers an event listener for a frame change ( addEventListener("frame 2", onFrameChange) ) On the 2nd frame of the MovieClip I am calling dispatchEvent(new Event("frame 2")); (I would prefer to not have this code on the frame, but I don't know what else to do) My two complaints with this method are that, first I have calls to addEventListener spread out across different class methods (I would rather have all UI event listeners registered in one method), and second that I have to dispatch those custom "onFrameChange" events. The second complaint grows exponentially for MovieClips that have more than just 2 frames. My so called solution feels makes me feel dirty and makes my brain hurt. I am looking for any advice on what to do differently. Perhaps there's a design pattern I should be looking at? Should I swallow my pride and write timeline code even though the rest of my application is written in class files (and I abhor the Flash IDE code editor)? I absolutely LOVE the event system, and have no problem coding applications with it, but I feel like I'm stuck thinking in terms of AS2 when working with mutl-frame movieclips and code. Any and all help would be greatly appreciated.

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  • Code refactoring c# question around several if statements performing the same check

    - by James Radford
    I have a method that has a load of if statements that seems a bit silly although I'm not sure how to improve the code. Here's an example. This logic was inside the view which is now in the controller which is far better but is there something I'm missing, maybe a design pattern that stops me having to check against panelCount < NumberOfPanelsToShow and handling the panelCount every condition? Maybe not, just feels ugly! Many thanks if (model.Train && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Train); panelCount++; } if (model.Car && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Car); panelCount++; } if (model.Hotel && panelCount < NumberOfPanelsToShow) { panelTypeList.Add(TheType.Hotel); panelCount++; } ...

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  • SQL Server 2008 Prior String Extract

    - by Saidur Rahman
    I have strings like the ones below in a SQL column. I want to extract them as a Gigabyte amount in aggregate. Example: Original Column ---------> Expected Output from a TSQL function ------------------------------------------- $15 / 1GB 24m + Intern 120MB ----------> 1.12 GB $19.95 / 500MB + $49.95 / 9GB Blackberry -----> 9.5GB $174.95 Blackberry 24GB + $10 / 1GB Datapack ----> 25GB $79 / 6GB --> 6GB Null --> Null $20 Plan --> 0GB Note: for our purpose, 1000MB = 1 GB (not 1024). The pattern is numbers followed by GB/MB, usually they are combined like 1GB (without any space but may sometimes may contain a space, it is not particularly important if hard to implement for this exception). Sometimes there are up to three or four instances of GB/MB occurring in the same string which are usually separated by a + sign (see row 2 and 3 of my example above). I have seen how we extract the dollar values in one of the answers where numbers were followed by $ or extract all integers in a string but I don't want to extract the dollar values or all the integers in a string. I just want the sum of GB/MB in the string.

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  • Memory allocation patterns in C++

    - by Mahatma
    I am confused about the memory allocation in C++ in terms of the memory areas such as Const data area, Stack, Heap, Freestore, Heap and Global/Static area. I would like to understand the memory allocation pattern in the following snippet. Can anyone help me to understand this. If there any thing more apart from the variable types mentioned in the example to help understand the concept better please alter the example. class FooBar { int n; //Stored in stack? public: int pubVar; //stored in stack? void foo(int param) //param stored in stack { int *pp = new int; //int is allocated on heap. n = param; static int nStat; //Stored in static area of memory int nLoc; //stored in stack? string str = "mystring"; //stored in stack? .. if(CONDITION) { static int nSIf; //stored in static area of memory int loopvar; //stored in stack .. } } } int main(int) { Foobar bar; //bar stored in stack? or a part of it? Foobar *pBar; //pBar is stored in stack pBar = new Foobar(); //the object is created in heap? What part of the object is stored on heap } EDIT: What confuses me is, if pBar = new Foobar(); stores the object on the heap, how come int nLoc; and int pubVar;, that are components of the object stored on stack? Sounds contradictory to me. Shouldn't the lifetime of pubvar and pBar be the same?

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  • looking for advise on importing excel into mysql with php

    - by Ole Media
    Alright, see if I can pick your brains from you all. I'm currently working on a project where all the information comes from different clients, the only thing in common is that the received data is done with excel. The excel spread sheet that they present is just a bunch of references and codes, and the problem than I'm facing is that I need the references and codes to be entered in certain format in order for the website to work. The perfect situation will be to go to each client and teach how I would need the data, but I can't do that because of the large number of clients, and more importantly I will be interrupting their work flow. Each client has its own codes and reference model and they are not willing to change their process The good news is that there is a standard pattern for the codes, but I'm talking close to 200 thousand codes with a bunch of combination. They way that we are currently solving the problem is that we have a person who checks each excel sheet received, runs a few macros, and manually fixes those codes in which the macro was not able to fix. The person that is doing this, is already burn out and frustrated and I would like to automatize this process with php. Suggestions?

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  • HTML5 Canvas and Game Programming

    - by LemonBeagle
    I hope this isn't too open ended. I'm wondering if there is a better (more battery-friendly) way of doing this -- I have a small HTML 5 game, drawn in a canvas (let's say 500x500). I have some objects whose positions I update every 50ms or so. My current implementation re-draws the entire canvas every 50ms. I can't imagine that being very good for battery life on mobile platforms. Is there a better way to do this? This must be a common pattern with games. EDIT: as requested, here are some more updates: Right now, the objects are geometric primitives drawn via arcs and lines. I'm not opposed to making these small png/jpg/gif files instead of that'd help out. These are small graphics -- just 15x15 or so. As the game progresses, more and more of the screen changes at a time. However, at the start, the screen changes relatively slowly (the objects randomly moved a few pixels every 50ms).

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  • Programatically adding,changing and removing controls bound to model objects (MVVM)

    - by Ittai
    I have the following scenario and I'm trying to decide how it can and should be implemented in silverlight and c# via MVVM. Scenario: I have the following objects in my scenario: MyModel, MyModelControl, MyView and MyViewModel. MyModelcontrol is a custom UserControl of mine and the rest I think are pretty much self explanatory. MyViewModel is a Subscriber of a message which hands it a Collection<MyModel> newCol and let's mark curCol as the current Collection<MyModel> that MyViewModel holds. I then want to programatically add MyModelControl controls for each MyModel instance which belongs to newCol and not to curCol. I also want to bind the MyModelControl instance to the corresponding MyModel instance. In a similar manner I want to remove the controls which don't belong now to the collection and I want to update a property for those which belong to both. I do not want to remove all controls which belong to curCol and then add all controls for newCol as the creation of MyModelControl is "expensive". I'd appreciate help with how this should be implemented in SL as I'm new to it and to the MVVM pattern. Comments regarding the design would also be welcomed. B.T.W This will run on Windows Phone 7 so I think there are some limitations on versions, if this is an issue please comment and I'll verify which versions exactly I can use on the phone.

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  • Design patterns for Caching Images in a MVC?

    - by Onema
    Hi, I'm designing an image cache system that will be used in an MVC CMS. The main purpose of the image cacher is to modify images: scale, crop, etc and cache them in the client site. I have created an image cache Model and Mapper that interact with the Database, to keep track of the images and know what kind of actions have been applied to them (scale, crop, etc). In addition to the Model and Mapper I have created a ImageCacher Class that is used by the API to manage the Model and image creation based on arguments passed by the client site, this class creates the images and generates the links to the images for the View. A coworker argued that I need to include the functionality of this last Class inside the Model, as the bulk of the logic should go in the model. I respectfully disagree with him since I feel the model's responsibility is to deal with the information about the images cached at the database level, and the responsibility of the ImageCacher Class is to create the url/image that we will be caching (keeping the single responsibility principle). In addition to this I believe that a model should not have Presentation-related features, like creating or showing images. Does anyone have any insight on this? is there a particular design pattern that would make this division of tasks clear and and the image cacher reusable? Should I add all the logic in the Model? Thank you.

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  • How to animate a path like it's being drawn, dot by dot? (Raphael.js)

    - by Anton
    How to animate a vector path like it's being drawn by hand? In other words, slowly show the path pixel by pixel. I'm using Raphaël.js, but if your answer is not library specific—like maybe there's some general programming pattern for doing that kind of thing (I'm fairly new to vector animation)—it's welcome! Update I know it's easy to do with straight paths, as easy as an example on that page:: path("M114 253").animate({path: "M114 253 L 234 253"}); But try to change code on that page, say, this way:: path("M114 26").animate({path: "M114 26 C 24 23 234 253 234 253"}); And you'll see what I mean. Path is certainly animated from it initial state (point "M114 26") to the end state (curve "C 24 23 234 253 234 253" starting on point "M114 26"), but not in a way specified in question, not like it's being drawn. (Sorry for not making clear from the start that I don't mean animating straight lines.) I don't see how animateAlong can do that either. It can animate an object along a path, and how can I make this path to gradually show itself while object is being animated along it?

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  • what patern is layerd architechture in asp.net ?

    - by haansi
    Hi, I am a asp.net developer and don't know much about patterns and architecture. I will very thankful if you can please guide me here. In my web applications I use 4 layers. Web site project (having web forms + code behind cs files, user controls + code behind cs files, master pages + code behind cs files) CustomTypesLayer a class library (having custom types, enumerations, DTOs, constructers, get, set and validations) BusinessLogicLayer a class library (having all business logic, rules and all calls to DAL functions) DataAccessLayer a class library( having just classes communicating to database.) -My user interface just calls BusinessLogicLayer. BusinessLogicLayer do proecessign in it self and for data it calls DataAccessLayer funtions. -Web forms do not calls directly DAL. -CustomTypesLayer is shared by all layers. Please guide me is this approach a pattern ? I though it may be MVC or MVP but pages have there code behind files as well which are confusing me. If it is no patren is it near to some patren ? pleaes guide thanks

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  • How do I check if a scalar has a compiled regex in it with Perl?

    - by Robert P
    Let's say I have a subroutine/method that a user can call to test some data that (as an example) might look like this: sub test_output { my ($self, $test) = @_; my $output = $self->long_process_to_get_data(); if ($output =~ /\Q$test/) { $self->assert_something(); } else { $self->do_something_else(); } } Normally, $test is a string, which we're looking for anywhere in the output. This was an interface put together to make calling it very easy. However, we've found that sometimes, a straight string is problematic - for example, a large, possibly varying number of spaces...a pattern, if you will. Thus, I'd like to let them pass in a regex as an option. I could just do: $output =~ $test if I could assume that it's always a regex, but ah, but the backwards compatibility! If they pass in a string, it still needs to test it like a raw string. So in that case, I'll need to test to see if $test is a regex. Is there any good facility for detecting whether or not a scalar has a compiled regex in it?

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  • Does the Eclipse editor have an equivalent of emacs's "align-regex"?

    - by rjray
    I've been using Eclipse pretty regularly for several years now, but I admit to not having explored all the esoterica it has to offer, particularly in the areas of what formatting features the editors offer. The main thing I miss from (X)emacs is the "align-regex" command, which let me take several lines into a region and then format them so that some common pattern in all lines was aligned. The simplest example of this is a series of variable assignments: var str = new String('aString'); var index = 0; var longCamelCaseObjectName = new LongNameObject(); After doing align-regex on "=", that would become: var str = new String('aString'); var index = 0; var longCamelCaseObjectName = new LongNameObject(); Now, you may have your own thoughts on stylistic (ab)use of white space and alignment, etc., but that's just an example (I'm actually trying to align a different kind of mess entirely). Can anyone tell me off-hand if there's an easy key-combo-shortcut for this in Eclipse? Or even a moderately-tricky one?

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  • Easy ways to investigate unknown Python APIs

    - by jedi_coder
    When studying a snippet of unknown Python code, I occasionally bump into the varName.methodName() pattern. To figure out what's this, I shall study the code more, find where varName was instantiated, find its type. So if varName proves to be an instance of ClassName class, I would knew that methodName() is a method of ClassName. Sometimes varName == self and methodName() is a method of this class, or a method inherited from some other class, if the current class is subclassing some other classes. Are there quick ways / tools that could take 'methodName' as input, scan over all installed Python modules and show which classes have methodName()? The closest thing related to this I know of is ipython. If I type a class name, then dot ('.') then TAB, it can show the class members. Instead of a class I could use a name of an object (which is an instance of a certain class) and it would work too. As soon as I choose a method name from the provided options, I can type '?' or '??' and get some help if there's a docstring. I wonder if ipython can do some intelligent scanning based only on 'methodName' string. If you know alternatives to ipython that could possibly help with this, please do suggest them.

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  • What kind of data do I pass into a Django Model.save() method?

    - by poswald
    Lets say that we are getting POSTed a form like this in Django: rate=10 items= [23,12,31,52,83,34] The items are primary keys of an Item model. I have a bunch of business logic that will run and create more items based on this data, the results of some db lookups, and some business logic. I want to put that logic into a save signal or an overridden Model.save() method of another model (let's call it Inventory). The business logic will run when I create a new Inventory object using this form data. Inventory will look like this: class Inventory(models.Model): picked_items = models.ManyToManyField(Item, related_name="items_picked_set") calculated_items = models.ManyToManyField(Item, related_name="items_calculated_set") rate = models.DecimalField() ... other fields here ... New calculated_items will be created based on the passed in items which will be stored as picked_items. My question is this: is it better for the save() method on this model to accept: the request object (I don't really like this coupling) the form data as arguments or kwargs (a list of primary keys and the other form fields) a list of Items (The caller form or view will lookup the list of Items and create a list as well as pass in the other form fields) some other approach? I know this is a bit subjective, but I was wondering what the general idea is. I've looked through a lot of code but I'm having a hard time finding a pattern I like.

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  • How to write curiously recurring templates with more than 2 layers of inheritance?

    - by Kyle
    All the material I've read on Curiously Recurring Template Pattern seems to one layer of inheritance, ie Base and Derived : Base<Derived>. What if I want to take it one step further? #include <iostream> using std::cout; template<typename LowestDerivedClass> class A { public: LowestDerivedClass& get() { return *static_cast<LowestDerivedClass*>(this); } void print() { cout << "A\n"; } }; template<typename LowestDerivedClass> class B : public A<LowestDerivedClass> { public: void print() { cout << "B\n"; } }; class C : public B<C> { public: void print() { cout << "C\n"; } }; int main() { C c; c.get().print(); // B b; // Intentionally bad syntax, // b.get().print(); // to demonstrate what I'm trying to accomplish return 0; } How can I rewrite this code to compile without errors (and output "C\nB\n")?

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  • What's the *right* way to handle a POST in FP?

    - by Malvolio
    I'm just getting started with FP and I'm using Scala, which may not be the best way, since I can always fall back to an imperative style if the going gets tough. I'd just rather not. I've got a very specific question that points to a broader lacuna in my understanding of FP. When a web application is processing a GET request, the user wants information that already exists on the web-site. The application only has to process and format the data in some way. The FB way is clear. When a web application is processing a POST request, the user wants change the information held on the site. True, the information is not typically held in application variables, it's in a database or a flat-file, but still, I get the feeling I'm not grokking FP properly. Is there a pattern for handling updates to static data in an FP language? My vague picture of this is that the application is handed the request and the then-current site state. The application does its thing and returns the new site-state. If the current site-state hasn't changed since the application started, the new state becomes the current state and the reply is sent back to the browser (this is my dim image of Clojure's style); if the current state has been changed (by another thread, well, something else happens ...

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