preprocessor definitions - Page 71

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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RegEx: difference between "(?:...) and normal parentheses

- by N0thing

>>> re.findall(r"(?:do|re|mi)+", "mimi") ['mimi'] >>> re.findall(r"(do|re|mi)+", "mimi") ['mi'] According to my understanding of the definitions, it should produce the same answer. The only difference between (...) and (?:...) should be whether or not we can use back-references later. Am I missing something? (...) Matches whatever regular expression is inside the parentheses, and indicates the start and end of a group; the contents of a group can be retrieved after a match has been performed, and can be matched later in the string with the \number special sequence, described below. To match the literals '(' or ')', use ( or ), or enclose them inside a character class: [(] [)]. (?:...) A non-capturing version of regular parentheses. Matches whatever regular expression is inside the parentheses, but the substring matched by the group cannot be retrieved after performing a match or referenced later in the pattern.

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Modules vs. Classes and their influence on descendants of ActiveRecord::Base

- by Chris

Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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Generating jquery 'rules' from business model to UI in asp.net mvc

- by jim

Hi all, I've had a good look around and am certain that there's no matching question on SO, so here goes. Has anyone created a 'helper' method on their model that generates jquery (or plain javascript) rules validation dynamically, based on the criteria/rules that are contained within the object and taken from a repository (i.e. DB). What i'm thinking of is a discrete set of partial views (and associated models) that have rules at the business logic 'level' and rather than (or in combination with) validating the rule(s) at postback, translating the same rules into tightly focussed jquery methods that work identically at client (js) and server (c#) levels. I can see benefits here re performance. Also, the rules definitions could be created in a single place (in c#) and the jquery generated off of that, thus allowing single edits to update both code streams. I appreciate that there would be limitations imposed by language specific contstraints but the general principle could be quite interesting if used appropriately. I'm also aware that testibility could be an issue when using two different language structures and hoping to achieve similar test outcomes - but those aside... any thoughts or experiences of similar out there?? cheers jimi

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Jersey, JAXB and getting an objectextending an abstract class as a parameter

- by krajol

I want to get an object as a parameter of a POST request. I got an abstract superclass that is called Promotion and subclasses Product and Percent. Here's how I try to get a request: @POST @Consumes(MediaType.APPLICATION_XML) @Produces(MediaType.APPLICATION_XML) @Path("promotion/") public Promotion createPromotion(Promotion promotion) { Product p = (Product) promotion; System.out.println(p.getPriceAfter()); return promotion; } and here's how I use JAXB in classes' definitions: @XmlRootElement(name="promotion") @XmlSeeAlso({Product.class,Percent.class}) public abstract class Promotion { //body } @XmlRootElement(name="promotion") public class Product extends Promotion { //body } @XmlRootElement(name="promotion") public class Percent extends Promotion { //body } So the problem now is when I send a POST request with a body like this: <promotion> <priceBefore>34.5</priceBefore> <marked>false</marked> <distance>44</distance> </promotion> and I try to cast it to Product (as in this case, fields 'marked' and 'distance' are from Promotion class and 'priceBefore' is from Product class) I get an Exception: java.lang.ClassCastException: Percent cannot be cast to Product. It seems like Percent is chosen as a 'default' subclass. Why is that and how can I get an object that is a Product?

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Is using advanced constructs (function, new, function calls) in JSON safe?

- by Vilx-

JSON is a nice way to pass complex data from my server side code to client side JavaScript. For example, in PHP I can write: <script type="text/javascript> var MyComplexVariable = <?= BigFancyObjectGraph.GetJSON() ?>; DoMagic(MyComplexVariable); </script> This is pretty cool, but sometimes you want to pass more than basic date, like dates or even function definitions. There is a simple and straightforward way of doing it too, like: <script type="text/javascript> var MyComplexVariable = { 'SimpleProperty' : 42, 'FunctionProperty' : function() { return 6*7; }, 'DateProperty' : new Date(989539200000), 'ArbitraryProperty' : GetTheMeaningOfLifeUniverseAndEverything() }; DoMagic(MyComplexVariable); </script> And this works like a charm on all browsers I've seen so far. But according to JSON.org such syntax is invalid. On the other hand, I've seen this syntax being used in very many places, including some popular JavaScript frameworks. So... Can I expect any problems if I use "unsupported" JSON features like the above? Why is it wrong or not?

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Question about using an access database as a resource file in Visual Studio.

- by user354303

Hi I am trying to embed a Microsoft Access database file into my Class assembly DLL. I want my code to reference the resource file and use it with a ADODB.Connection object. Any body know a simpler way, or an easier way? Or what is wrong with my code, when i added the resource file it added me dataset definitions, but i have no idea what to do with those. The connection string I am trying below is from an automatically generated app.config. I did add the item as a resource... using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; using ConsoleApplication1.Resources;//SPPrinterLicenses using System.Data.OleDb; using ADODB; using System.Configuration; namespace ConsoleApplication1 { class SharePointPrinterManager { public static bool IsValidLicense(string HardwareID) { OleDbDataAdapter da = new OleDbDataAdapter(); DataSet ds = new DataSet(); ADODB.Connection adoCn = new Connection(); ADODB.Recordset adoRs = new Recordset(); //**open command below fails** adoCn.Open( @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Resources\SPPrinterLicenses.accdb;Persist Security Info=True", "", "", 1); adoRs.Open("Select * from AllWorkstationLicenses", adoCn, ADODB.CursorTypeEnum.adOpenForwardOnly, ADODB.LockTypeEnum.adLockReadOnly, 1); da.Fill(ds, adoRs, "AllworkstationLicenses"); adoCn.Close(); DataTable dt = new DataTable(); //ds.Tables. return true; } } }

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Greasemonkey failing to GM_setValue()

- by HonoredMule

I have a Greasemonkey script that uses a Javascript object to maintain some stored objects. It covers quite a large volume of information, but substantially less than it successfully stored and retrieved prior to encountering my problem. One value refuses to save, and I can not for the life of me determine why. The following problem code: Works for other larger objects being maintained. Is presently handling a smaller total amount of data than previously worked. Is not colliding with any function or other object definitions. Can (optionally) successfully save the problem storage key as "{}" during code startup. this.save = function(table) { var tables = this.tables; if(table) tables = [table]; for(i in tables) { logger.log(this[tables[i]]); logger.log(JSON.stringify(this[tables[i]])); GM_setValue(tables[i] + "_" + this.user, JSON.stringify(this[tables[i]])); logger.log(tables[i] + "_" + this.user + " updated"); logger.log(GM_getValue(tables[i] + "_" + this.user)); } } The problem is consistently reproducible and the logging statments produce the following output in Firebug: Object { 54,10 = Object } // Expansion shows complete contents as expected, but there is one oddity--Firebug highlights the array keys in purple instead of the usual black for anonymous objects. {"54,10":{"x":54,"y":10,"name":"Lucky Pheasant"}} // The correctly parsed string. bookmarks_HonoredMule saved undefined I have tried altering the format of the object keys, to no effect. Further narrowing down the issue is that this particular value is successfully saved as an empty object ("{}") during code initialization, but skipping that also does not help. Reloading the page confirms that saving of the nonempty object truly failed. Any idea what could cause this behavior? I've thoroughly explored the possibility of hitting size constraints, but it doesn't appear that can be the problem--as previously mentioned, I've already reduced storage usage. Other larger objects save still, and the total number of objects, which was not high already, has further been reduced by an amount greater than the quantity of data I'm attempting to store here.

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Is it bad practise to initialise fields outside of an explicit constructor

- by MrTortoise

So its monday and we are arguing about coding practises. The examples here are a litttle too simple, but the real deal has several constructors. In order to initialise the simple values (eg dates to their min value) I have moved the code out of the constructors and into the field definitions. public class ConstructorExample { string _string = "John"; } public class ConstructorExample2 { string _string; public ConstructorExample2() { _string = "John"; } } How should it be done by the book. I tend to be very case by case and so am maybe a little lax abotu this kind of thing. However i feel that accams razor tells me to move the initialisation out of multiple constructors. Of course I could always move this shared initialisation into a private method. The question is essentially ... is initialising fields where they are defined as opposed to the constructor bad in any way? The argument I am facing is one of error handling, but i do not feel it is relevant as there are no possible exceptions that won't be picked up at compile time.

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Memory allocation for a matrix in C

- by Snogzvwtr

Why is the following code resulting in Segmentation fault? (I'm trying to create two matrices of the same size, one with static and the other with dynamic allocation) #include <stdio.h> #include <stdlib.h> //Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } Weirdly enough, if I comment out one of the matrix definitions, the code runs fine. Like this: #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; //int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } or #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; //int** b = (int**) malloc(sizeof(int*) * X); //for(i=0; i<X; i++){ // b[i] = malloc (sizeof(int) * Y); //} } I'm running gcc on Linux on a 32-bit machine.

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Query returning related assets

- by GMo

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complex regular expression task

- by Don Don

Hi, What regular expressions do I need to extract section title(s) in a text file? So, in the following sample text, I'd like to extract "Communication and Leadership" "1.Self-Knowledge" "2. Humility" "(3) Clear Thinking". Many thanks. Communication and Leadership True leaders understand that, rather than forcing their followers into a preconceived mold, their job is to motivate and organize followers to collectively accomplish goals that are in everyone's interests. The ability to communicate this to co-workers and followers is critical to the effectiveness of leadership. 1.Self-Knowledge Superior leaders are able to devote their skills and energies to leadership of a group because they have worked through personal issues to the point where they know themselves thoroughly. A high level of self-knowledge is a prerequisite to effective communication skills, because the things that you communicate as a leader are coming from within. 2. Humility This subversion of personal preference requires a certain level of humility. Although popular definitions of leaders do not always see them as humble, the most effective leaders actually are. This humility may not be expressed in self-effacement, but in a total commitment to the goals of the organization. Humility requires an understanding of one's own relative unimportance in comparison to larger systems. (3) Clear Thinking Clarity of thinking translates into clarity of communication. A leader whose goals or personal analysis is muddled will tend to deliver unclear or ambiguous directions to followers, leading to confusion and dissatisfaction. A leader with a clear mind who is not ambivalent about her purposes will communicate what needs to be done in a s traightforward and unmistakable manner.

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Merge XML files with configurable rules (context: Maven POMs, Java)

- by Patrick Bergner

Hi, I'm currently writing some kind of a Maven POM preprocessor that assembles a POM for a project from multiple input files (basically a template and a module specific file). The files are hierarchically ordered (template = most general, module specific = least general). The problem is now to merge these files into a single POM file. Long story short or if you're not familiar with Maven: a POM looks like this (shortened): <project> <modelVersion>4.0.0</modelVersion> <dependencies> <dependency> <groupId>org.apache.maven</groupId> <artifactId>maven-core</artifactId> </dependency> </dependencies> </project> Basically the merger shall replace all values of the more general file with the values of the more specific file (i.e. singletons, e.g. the <modelVersion> above) but there are certain elements where the merger shall add the more certain element to a parent (i.e. collections, e.g. <dependency> elements shall always be added to the <dependencies> element and no <dependency> element shall be replaced by another). A more detailed example with definition of desired output: File A: <project> <modelVersion>A</modelVersion> <dependencies> <dependency> <groupId>groupIdA</groupId> <artifactId>artifactIdA</artifactId> </dependency> </dependencies> </project> File B: <project> <modelVersion>B</modelVersion> <dependencies> <dependency> <groupId>groupIdB</groupId> <artifactId>artifactIdB</artifactId> </dependency> </dependencies> </project> Desired output: <project> <modelVersion>B</modelVersion> <dependencies> <dependency> <groupId>groupIdA</groupId> <artifactId>artifactIdA</artifactId> </dependency> <dependency> <groupId>groupIdB</groupId> <artifactId>artifactIdB</artifactId> </dependency> </dependencies> </project> The set of collection type elements are known and should be configurable (preferably via a set of XPath expressions). A Java based solution is appreciated. What looked most promising so far was the tool mentioned here but the MERGE action produces something like <dependency> <groupId>groupIdAgroupIdB</groupId> <artifactId>artifactIdAartifactIdB</artifactId> </dependency> when merging, which is not what I need. Any ideas? Thanks for your help!

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Problems with Window Functions Wndproc and about

- by BrianHuangverinem

I really having problems with this problem ,it would be nice if someone help me on this. Every time I try to build my source file the same errors occur every time for the two window functions CALLBACK Wndproc and CALLBACK About. error: "local function definitions are illegal" Can you tell me what mistake I made? LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; wmId = LOWORD(wParam); wmEvent = HIWORD(wParam); switch (message) { case WM_COMMAND: // Parse the menu selections: switch (wmId) { case IDM_ABOUT: DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About); break; case IDM_EXIT: DestroyWindow(hWnd); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } break; case WM_PAINT: hdc = BeginPaint(hWnd, &ps); CaptureImage(hWnd); EndPaint(hWnd, &ps); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } return 0; } // Message handler for about box. INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) { UNREFERENCED_PARAMETER(lParam); switch (message) { case WM_INITDIALOG: return (INT_PTR)TRUE; case WM_COMMAND: if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL) { EndDialog(hDlg, LOWORD(wParam)); return (INT_PTR)TRUE; } break; } return (INT_PTR)FALSE; }

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iOS - is it possible to cache CGContextDrawImage?

- by woot586

I used the timing profile tool to identify that 95% of the time is spent calling the function CGContextDrawImage. In my app there are a lot of duplicate images repeatably being chopped from a sprite map and drawn to the screen. I was wondering if it was possible to cache the output of CGContextDrawImage in an NSMutableDictionay, then if the same sprite is requested again it can be just pull it from the cache rather than doing all the work of clipping and rendering it again. This is what i’ve got but I have not been to successful: Definitions if(cache == NULL) cache = [[NSMutableDictionary alloc]init]; //Identifier based on the name of the sprite and location within the sprite. NSString* identifier = [NSString stringWithFormat:@"%@-%d",filename,frame]; Adding to cache CGRect clippedRect = CGRectMake(0, 0, clipRect.size.width, clipRect.size.height); CGContextClipToRect( context, clippedRect); //create a rect equivalent to the full size of the image //offset the rect by the X and Y we want to start the crop //from in order to cut off anything before them CGRect drawRect = CGRectMake(clipRect.origin.x * -1, clipRect.origin.y * -1, atlas.size.width, atlas.size.height); //draw the image to our clipped context using our offset rect CGContextDrawImage(context, drawRect, atlas.CGImage); [cache setValue:UIGraphicsGetImageFromCurrentImageContext() forKey:identifier]; UIGraphicsEndImageContext(); Rendering a cached sprite There is probably a better way to render CGImage which is my ultimate caching goal but at the moment I’m just looking to successfully render the cached image out however this has not been successful. UIImage* cachedImage = [cache objectForKey:identifier]; if(cachedImage){ NSLog(@"Cached %@",identifier); CGRect imageRect = CGRectMake(0, 0, cachedImage.size.width, cachedImage.size.height); if (NULL != UIGraphicsBeginImageContextWithOptions) UIGraphicsBeginImageContextWithOptions(imageRect.size, NO, 0); else UIGraphicsBeginImageContext(imageRect.size); //Use draw for now just to see if the image renders out ok CGContextDrawImage(context, imageRect, cachedImage.CGImage); UIGraphicsEndImageContext(); }

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JavaCC: How can I specify which token(s) are expected in certain context?

- by java.is.for.desktop

Hello, everyone! I need to make JavaCC aware of a context (current parent token), and depending on that context, expect different token(s) to occur. Consider the following pseudo-code: TOKEN <abc> { "abc*" } // recognizes "abc", "abcd", "abcde", ... TOKEN <abcd> { "abcd*" } // recognizes "abcd", "abcde", "abcdef", ... TOKEN <element1> { "element1" "[" expectOnly(<abc>) "]" } TOKEN <element2> { "element2" "[" expectOnly(<abcd>) "]" } ... So when the generated parser is "inside" a token named "element1" and it encounter "abcdef" it recognizes it as <abc>, but when its "inside" a token named "element2" it recognizes the same string as <abcd>. element1 [ abcdef ] // aha! it can only be <abc> element2 [ abcdef ] // aha! it can only be <abcd> If I'm not wrong, it would behave similar to more complex DTD definitions of an XML file. So, how can one specify, in which "context" which token(s) are valid/expected? NOTE: It would be not enough for my real case to define a kind of "hierarchy" of tokens, so that "abcdef" is always first matched against <abcd> and than <abc>. I really need context-aware tokens.

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How to format dates in Jahia 6 CMS?

- by dpb

I am helping a friend of mine put up a site for his business. I’ve read different posts and sites trying to find the ideal CMS tool, but people have different views of what is the best, so I finally just picked one of them at random. So I went for an evaluation of Jahia 6.0-CE. As you’ve probably guessed by now, I don’t have so much experience with CMS tools. I just want to setup the CMS, write the templates for the site and let my friend manage the content from there on. So I extracted the sources from SVN and went for a test drive. I managed to create some simple templates to get a hang of things but now I have an issue with a date format. In my definitions.cnd I declared the field like so: date myDateField (datetimepicker[format='dd.MM.yyyy']) This is formatted in the page and the selector also presents this in the dd.MM.yyyy format when inserting the content. But how about sites in other countries, countries that represent the date as MM.dd.yyyy for example? If I specify the format in the CND, hard coded, how can I change this later on so that it adapts based on the browser’s language? Do I extract the content from the repository and format it by hand in the JSP template based on a Locale, or is there a better way? Thank you.

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XmlSerializer construction with same named extra types

- by NoizWaves

Hey, I am hitting trouble constructing an XmlSerializer where the extra types contains types with the same Name (but unique Fullname). Below is an example that illustrated my scenario. Type definitions in external assembly I cannot manipulate: public static class Wheel { public enum Status { Stopped, Spinning } } public static class Engine { public enum Status { Idle, Full } } Class I have written and have control over: public class Car { public Wheel.Status WheelStatus; public Engine.Status EngineStatus; public static string Serialize(Car car) { var xs = new XmlSerializer(typeof(Car), new[] {typeof(Wheel.Status),typeof(Engine.Status)}); var output = new StringBuilder(); using (var sw = new StringWriter(output)) xs.Serialize(sw, car); return output.ToString(); } } The XmlSerializer constructor throws a System.InvalidOperationException with Message "There was an error reflecting type 'Engine.Status'" This exception has an InnerException of type System.InvalidOperationException and with Message "Types 'Wheel.Status' and 'Engine.Status' both use the XML type name, 'Status', from namespace ''. Use XML attributes to specify a unique XML name and/or namespace for the type." Given that I am unable to alter the enum types, how can I construct an XmlSerializer that will serialize Car successfully?

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static initialization confusion

- by Happy Mittal

I am getting very confused in some concepts in c++. For ex: I have following two files //file1.cpp class test { static int s; public: test(){s++;} }; static test t; int test::s=5; //file2.cpp #include<iostream> using namespace std; class test { static int s; public: test(){s++;} static int get() { return s; } }; static test t; int main() { cout<<test::get()<<endl; } Now My question is : 1. How two files link successfully even if they have different class definitions? 2. Are the static member s of two classes related because I get output as 7. Please explain this concept of statics.

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Efficient way to remove empty lists from lists without evaluating held expressions?

- by Alexey Popkov

In previous thread an efficient way to remove empty lists ({}) from lists was suggested: Replace[expr, x_List :> DeleteCases[x, {}], {0, Infinity}] Using the Trott-Strzebonski in-place evaluation technique this method can be generalized for working also with held expressions: f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}] This solution is more efficient than the one based on ReplaceRepeated: f2[expr_] := expr //. {left___, {}, right___} :> {left, right} But it has one disadvantage: it evaluates held expressions if they are wrapped by List: In[20]:= f1[Hold[{{}, 1 + 1}]] Out[20]= Hold[{2}] So my question is: what is the most efficient way to remove all empty lists ({}) from lists without evaluating held expressions? The empty List[] object should be removed only if it is an element of another List itself. Here are some timings: In[76]:= expr = Tuples[Tuples[{{}, {}}, 3], 4]; First@Timing[#[expr]] & /@ {f1, f2, f3} pl = Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}]; First@Timing[#[pl]] & /@ {f1, f2, f3} Out[77]= {0.581, 0.901, 5.027} Out[78]= {0.12, 0.21, 0.18} Definitions: Clear[f1, f2, f3]; f3[expr_] := FixedPoint[ Function[e, Replace[e, {a___, {}, b___} :> {a, b}, {0, Infinity}]], expr]; f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}]; f2[expr_] := expr //. {left___, {}, right___} :> {left, right};

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Finding patterns of failure in a Unit Test

- by Pekka

I'm new to Unit Testing, and I'm only getting into the routine of building test suites. I have what is going to be a rather large project that I want to build tests for from the start. I'm trying to figure out general strategies and patterns for building test suites. When you look at a class, many tests come to you obviously due to the nature of the class. Say for a "user account" class with basic CRUD operations, being related to a database table, we will want to test - well, the CRUD. creating an object and seeing whether it exists query its properties change some properties change some properties to incorrect values and delete it again. As for how to break things, there are "fail" tests common to most CRUD classes like: Invalid input data types A number as the ID key that exceeds the range of the chosen data type Input in an incorrect character encoding Input that is too long And so on and so on. For a unit test concerned with file operations, the list of "breaking things" could be Invalid characters in file name File name too long File name uses incorrect protocol or path I'm pretty sure similar patterns - applicable beyond the unit test one is currently working on - can be found for most units that are being tested. Now my question is: Am I correct in seeing such "breaking patterns"? Or am I getting something completely wrong about Unit testing, and if I did it right, this wouldn't be an issue at all? Is Unit Testing as a process of finding as many ways to break the unit as possible the right way to go? If I am correct: Are there existing definitions, lists, cheat sheets for such patterns? Are there any provisions (mainly in PHPUnit, as that's the framework I'm working in) to automate such patterns? Is there any assistance - in the form of check lists, or software - to aid in writing complete tests?

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How can i design a DB where the user can define the fields and types of a detail table in a M-D rela

- by Simon

My application has one table called 'events' and each event has approx 30 standard fields, but also user defined fields that could be any name or type, in an 'eventdata' table. Users can define these event data tables, by specifying x number of fields (either text/double/datetime/boolean) and the names of these fields. This 'eventdata' (table) can be different for each 'event'. My current approach is to create a lookup table for the definitions. So if i need to query all 'event' and 'eventdata' per record, i do so in a M-D relaitionship using two queries (i.e. select * from events, then for each record in 'events', select * from 'some table'). Is there a better approach to doing this? I have implemented this so far, but most of my queries require two distinct calls to the DB - i cannot simply join my master 'events' table with different 'eventdata' tables for each record in in 'events'. I guess my main question is: can i join my master table with different detail tables for each record? E.g. SELECT E.*, E.Tablename FROM events E LEFT JOIN 'E.tablename' T ON E._ID = T.ID If not, is there a better way to design my database considering i have no idea on how many user defined fields there may be and what type they will be.

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sql queries slower than expected

- by neubert

Before I show the query here are the relevant table definitions: CREATE TABLE phpbb_posts ( topic_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, poster_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, KEY topic_id (topic_id), KEY poster_id (poster_id), ); CREATE TABLE phpbb_topics ( topic_id mediumint(8) UNSIGNED NOT NULL auto_increment ); Here's the query I'm trying to do: SELECT p.topic_id, p.poster_id FROM phpbb_topics AS t LEFT JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> ... WHERE p.poster_id IS NULL; Basically, the query is an attempt to find all topics where the number of times someone other than the target user has posted in is zero. In other words, the topics where the only person who has posted is the target user. Problem is that query is taking a super long time. My general assumption when it comes to SQL is that JOINs of any are super fast and can be done in no time at all assuming all relevant columns are primary or foreign keys (which in this case they are). I tried out a few other queries: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id; That returns 353340 pretty quickly. I then do these: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> 77198; SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id WHERE p.poster_id <> 77198; And both of those take quite a while (between 15-30 seconds). If I change the < to a = it takes no time at all. Am I making some incorrect assumptions? Maybe my DB is just foobar'd?

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Trouble using 'eval' to define a toplevel function when called from within an object.

- by mschaef

I've written (in JavaScript) an interactive read-eval-print-loop that is encapsulated within an object. However, I recently noticed that toplevel function definitions specified to the interpreter do not appear to be 'remembered' by the interpreter. After some diagnostic work, I've reduced the core problem to this: var evaler = { eval: function (str) { return eval(str); }, }; eval("function t1() { return 1; }"); // GOOD evaler.eval("function t2() { return 2; }"); // FAIL After running this script, I have a definition for t1, and no defintion for t2. The act of calling eval from within evaler is sufficiently different from the toplevel call that the global definition does not get recorded. What does happen is that the call to evaler.eval returns a function object, so I'm presuming that t2 is being defined and stored in some other set of bindings that I don't have access to. (It's not defined as a member in evaler.) Is there any easy fix for this? I've tried all sorts of fixes, and haven't stumbled upon one that works. (Most of what I've done has centered around putting the call to eval in an anonymous function, and altering the way that's called, chainging __parent__, etc.) Any thoughts on how to fix this?

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Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

- by DanM

I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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