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• What is a fast way to set debugging code at a given line in a function?

  - by Josh O'Brien

  Preamble: R's trace() is a powerful debugging tool, allowing users to "insert debugging code at chosen places in any function". Unfortunately, using it from the command-line can be fairly laborious. As an artificial example, let's say I want to insert debugging code that will report the between-tick interval calculated by pretty.default(). I'd like to insert the code immediately after the value of delta is calculated, about four lines up from the bottom of the function definition. (Type pretty.default to see where I mean.) To indicate that line, I need to find which step in the code it corresponds to. The answer turns out to be step list(c(12, 3, 3)), which I zero in on by running through the following steps: as.list(body(pretty.default)) as.list(as.list(body(pretty.default))[[12]]) as.list(as.list(as.list(body(pretty.default))[[12]])[[3]]) as.list(as.list(as.list(body(pretty.default))[[12]])[[3]])[[3]] I can then insert debugging code like this: trace(what = 'pretty.default', tracer = quote(cat("\nThe value of delta is: ", delta, "\n\n")), at = list(c(12,3,3))) ## Try it a <- pretty(c(1, 7843)) b <- pretty(c(2, 23)) ## Clean up untrace('pretty.default') Questions: So here are my questions: Is there a way to print out a function (or a parsed version of it) with the lines nicely labeled by the steps to which they belong? Alternatively, is there another easier way, from the command line, to quickly set debugging code for a specific line within a function? Addendum: I used the pretty.default() example because it is reasonably tame, but with real/interesting functions, repeatedly using as.list() quickly gets tiresome and distracting. Here's an example: as.list(as.list(as.list(as.list(as.list(as.list(as.list(as.list(as.list(body(# model.frame.default))[[26]])[[3]])[[2]])[[4]])[[3]])[[4]])[[4]])[[4]])[[3]]

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• P/Invoke declarations should not be safe-critical

  - by Bobrovsky

  My code imports following native methods: DeleteObject, GetFontData and SelectObject from gdi32.dll GetDC and ReleaseDC from user32.dll I want to run the code in full trust and medium trust environments (I am fine with exceptions being thrown when these imported methods are indirectly used in medium trust environments). When I run Code Analysis on the code I get warnings like: CA5122 P/Invoke declarations should not be safe-critical. P/Invoke method 'GdiFont.DeleteObject(IntPtr)' is marked safe-critical. Since P/Invokes may only be called by critical code, this declaration should either be marked as security critical, or have its annotation removed entirely to avoid being misleading. Could someone explain me (in layman terms) what does this warning really mean? I tried putting these imports in static SafeNativeMethods class as internal static methods but this doesn't make the warnings go away. I didn't try to put them in NativeMethods because after reading this article I am unsure that it's the right way to go because I don't want my code to be completely unusable in medium trust environments (I think this will be the consequence of moving imports to NativeMethods). Honestly, I am pretty much confused about the real meaning of the warning and consequences of different options to suppressing it. Could someone shed some light on all this? EDIT: My code target .NET 2.0 framework. Assembly is marked with [assembly: AllowPartiallyTrustedCallers] Methods are declared like this: [DllImport("gdi32")] internal static extern int DeleteObject(HANDLE hObject);

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• Android ADB has moved and Eclipse is looking in the old place

  - by Peter Nelson

  I did an SDK update last night and it moved adb.exe. In its place it left a file called "adb_has_moved.txt" saying The adb tool has moved to platform-tools/ If you don't see this directory in your SDK, launch the SDK and AVD Manager (execute the android tool) and install "Android SDK Platform-tools" Please also update your PATH environment variable to include the platform-tools/ directory, so you can execute adb from any location. So I did all that, including the PATH and now I can start adb.exe from any DOS prompt. But I still can't start it from Eclipse (Galileo 3.52). When I try it says Location of the Android SDK has not been set up in the preferences ... which is not true. The SDK IS set up in Preferences. The real problem is at the top of the Preferences window where it says "Could not find C:\SDK\android-sdk-windows\ tools \adb.exe!" ...No kidding - the update moved it to C:\SDK\android-sdk-windows\ platform-tools. Because it's specifying a specific (wrong) path Eclipse is bypassing the PATH variable. So how do I get Eclipse to look in the right place?

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• What is a good way to assign order #s to ordered rows in a table in Sybase

  - by DVK

  I have a table T (structure below) which initially contains all-NULL values in an integer order column: col1 varchar(30), col2 varchar(30), order int NULL I also have a way to order the "colN" columns, e.g. SELECT * FROM T ORDER BY some_expression_involving_col1_and_col2 What's the best way to assign - IN SQL - numeric order values 1-N to the order table, so that the order values match the order of rows returned by the above ORDER BY? In other words, I would like a single query (Sybase SQL syntax so no Oracle's rowcount) which assigns order values so that SELECT * FROM T ORDER BY order returns 100% same order of rows as the query above. The query does NOT necessarily need to update the table T in place, I'm OK with creating a copy of the table T2 if that'll make the query simpler. NOTE1: A solution must be real query or a set of queries, not involving a loop or a cursor. NOTE2: Assume that the data is uniquely orderable according to the order by above - no need to worry about situation when 2 rows can be assigned the same order at random. NOTE3: I would prefer a generic solution, but if you wish a specific example of ordering expression, let's say: SELECT * FROM T ORDER BY CASE WHEN col1="" THEN "AAAAAA" ELSE col1 END, ISNULL(col2, "ZZZ")

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• URL shortening: using inode as short name?

  - by Licky Lindsay

  The site I am working on wants to generate its own shortened URLs rather than rely on a third party like tinyurl or bit.ly. Obviously I could keep a running count new URLs as they are added to the site and use that to generate the short URLs. But I am trying to avoid that if possible since it seems like a lot of work just to make this one thing work. As the things that need short URLs are all real physical files on the webserver my current solution is to use their inode numbers as those are already generated for me ready to use and guaranteed to be unique. function short_name($file) { $ino = @fileinode($file); $s = base_convert($ino, 10, 36); return $s; } This seems to work. Question is, what can I do to make the short URL even shorter? On the system where this is being used, the inodes for newly added files are in a range that makes the function above return a string 7 characters long. Can I safely throw away some (half?) of the bits of the inode? And if so, should it be the high bits or the low bits? I thought of using the crc32 of the filename, but that actually makes my short names longer than using the inode. Would something like this have any risk of collisions? I've been able to get down to single digits by picking the right value of "$referencefile". function short_name($file) { $ino = @fileinode($file); // arbitrarily selected pre-existing file, // as all newer files will have higher inodes $ino = $ino - @fileinode($referencefile); $s = base_convert($ino, 10, 36); return $s; }

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• C#/LINQ: How to define generically a keySelector for a templated class before calling OrderBy

  - by PierrOz

  Hi Folks, I have the following class defined in C# class myClass<T,U> { public T PropertyOne { get; set; } public U PropertyTwo { get; set; } } I need to write a function that reorder a list of myClass objects and takes two other parameters which define how I do this reorder: does my reordering depend on PropertyOne or PropertyTwo and is it ascending or descending. Let's say this two parameters are boolean. With my current knowledge in LINQ, I would write: public IList<myClass<T,U>> ReOrder(IList<myClass<T,U>> myList, bool usePropertyOne, bool ascending) { if (usePropertyOne) { if (ascending) { return myList.OrderBy(o => o.PropertyOne).ToList(); } else { return myList.OrderByDescending(o => o.PropertyOne).ToList(); } } else { if (ascending) { return myList.OrderBy(o => o.PropertyTwo).ToList(); } else { return myList.OrderByDescending(o => o.PropertyTwo).ToList(); } } } What could be a more efficient/elegant way to do that ? How can I declare the Func,TResult keySelector object to reuse when I call either OrderBy or OrderByDescending? I'm interesting in the answer since in my real life, I can have more than two properties.

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• How can I SETF an element in a tree by an accessor?

  - by Willi Ballenthin

  We've been using Lisp in my AI course. The assignments I've received have involved searching and generating tree-like structures. For each assignment, I've ended up writing something like: (defun initial-state () (list 0 ; score nil ; children 0 ; value 0)) ; something else and building my functions around these "states", which are really just nested lists with some loosely defined structure. To make the structure more rigid, I've tried to write accessors, such as: (defun state-score ( state ) (nth 2 state)) This works for reading the value (which should be all I need to do in a nicely functional world. However, as time crunches, and I start to madly hack, sometimes I want a mutable structure). I don't seem to be able to SETF the returned ...thing (place? value? pointer?). I get an error with something like: (setf (state-score *state*) 10) Sometimes I seem to have a little more luck writing the accessor/mutator as a macro: (defmacro state-score ( state ) `(nth 2 ,state)) However I don't know why this should be a macro, so I certainly shouldn't write it as a macro (except that sometimes it works. Programming by coincidence is bad). What is an appropriate strategy to build up such structures? More importantly, where can I learn about whats going on here (what operations affect the memory in what way)?

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• How to simulate OutOfMemory exception

  - by Gacek

  I need to refactor my project in order to make it immune to OutOfMemory exception. There are huge collections used in my project and by changing one parameter I can make my program to be more accurate or use less of the memory... OK, that's the background. What I would like to do is to run the routines in a loop: Run the subroutines with the default parameter. Catch the OutOfMemory exception, change the parameter and try to run it again. Do the 2nd point until parameters allow to run the subroutines without throwing the exception (usually, there will be only one change needed). Now, I would like to test it. I know, that I can throw the OutOfMemory exception on my own, but I would like to simulate some real situation. So the main question is: Is there a way of setting some kind of memory limit for my program, after reaching which the OutOfMemory exception will be thrown automatically? For example, I would like to set a limit, let's say 400MB of memory for my whole program to simulate the situation when there is such an amount of memory available in the system. Can it be done?

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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• Add delay and focus for a dead simple accordion jquery

  - by kuswantin

  I found the code somewhere in the world, and due to its dead simple nature, I found some things in need to fix, like when hovering the trigger, the content is jumping up down before it settled. I have tried to change the trigger from the title of the accordion block to the whole accordion block to no use. I need help to add a delay and only do the accordion when the cursor is focus in the block. I have corrected my css to make sure the block is covering the hidden part as well when toggled. Here is my latest modified code: var acTrig = ".accordion .title"; $(acTrig).hover(function() { $(".accordion .content").slideUp("normal"); $(this).next(".content").slideDown("normal"); }); $(acTrig).next(".content").hide(); $(acTrig).next(".content").eq(0).css('display', 'block'); This is the HTML: <div class="accordion clearfix"> <div class="title">some Title 1</div> <div class="content"> some content blah </div> </div> <div class="accordion clearfix"> <div class="title">some Title 2</div> <div class="content"> some content blah </div> </div> <div class="accordion clearfix"> <div class="title">some Title 3</div> <div class="content"> some content blah </div> </div> I think I need a way to stop event bubbling somewhere around the code, but can't get it right. Any help would be very much appreciated. Thanks as always.

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• Case Insensitive Ternary Search Tree

  - by Yan Cheng CHEOK

  I had been using Ternary Search Tree for a while, as the data structure to implement a auto complete drop down combo box. Which means, when user type "fo", the drop down combo box will display foo food football The problem is, my current used of Ternary Search Tree is case sensitive. My implementation is as follow. It had been used by real world for around 1++ yeas. Hence, I consider it as quite reliable. My Ternary Search Tree code However, I am looking for a case insensitive Ternary Search Tree, which means, when I type "fo", the drop down combo box will show me foO Food fooTBall Here are some key interface for TST, where I hope the new case insentive TST may have similar interface too. /** * Stores value in the TernarySearchTree. The value may be retrieved using key. * @param key A string that indexes the object to be stored. * @param value The object to be stored in the tree. */ public void put(String key, E value) { getOrCreateNode(key).data = value; } /** * Retrieve the object indexed by key. * @param key A String index. * @return Object The object retrieved from the TernarySearchTree. */ public E get(String key) { TSTNode<E> node = getNode(key); if(node==null) return null; return node.data; } An example of usage is as follow. TSTSearchEngine is using TernarySearchTree as the core backbone. Example usage of Ternary Search Tree // There is stock named microsoft and MICROChip inside stocks ArrayList. TSTSearchEngine<Stock> engine = TSTSearchEngine<Stock>(stocks); // I wish it would return microsoft and MICROCHIP. Currently, it just return microsoft. List<Stock> results = engine.searchAll("micro");

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• Sell me Distributed revision control

  - by ring bearer

  I know 1000s of similar topics floating around. I read at lest 5 threads here in SO But why am I still not convinced about DVCS? I have only following questions (note that I am selfishly worried only about Java projects) What is the advantage or value of committing locally? What? really? All modern IDEs allows you to keep track of your changes? and if required you can restore a particular change. Also, they have a feature to label your changes/versions at IDE level!? what if I crash my hard drive? where did my local repository go? (so how is it cool compared to checking in to a central repo?) Working offline or in an air plane. What is the big deal?In order for me to build a release with my changes, I must eventually connect to the central repository. Till then it does not matter how I track my changes locally. Ok Linus Torvalds gives his life to Git and hates everything else. Is that enough to blindly sing praises? Linus lives in a different world compared to offshore developers in my mid-sized project? Pitch me!

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• How to publish internal data to the internet - as simple as possible

  - by mlarsen

  We have a .net 2-tier application where a desktop program is talking to a database. We support MS SQL Server 2000, 2005, 2008 and Oracle 9, 10 and 11. The application is sold, not as shrink-wrap, but pretty close. It is quite important for us that the installation and configuration is as easy as possible as installation instructions are usually supplied in written form to the customers internal IT-department. Our application is usually not seen as mission critical for the IT-department, so we need to keep their work down to a minimum. Now we are starting to get wishes for a web application build on top of the same data. The web application will be hosted by us and delivered as a SaaS application. Now the challenge is how to move data back and forth between the web application and the customers internal database. as I see it we have some requirements: We must be ready to handle the situation where the customers database is not accessible from the DMZ. I guess the easiest solution is that all communication is initiated from inside the customers lan. As little firewall configuration as possible. The best is if we can run without any special configuration as long as outgoing traffic from the customers lan are not blocked. If we need something changed in the firewall, we must be able to document that the change is secure. It doesn't have to be real time. Moving data in batches every ten minutes or so is OK. Data moves both ways, but not the same tables, so we don't have to support merges. It would be nice if we don't have to roll our own framework completely. Looking forward to hear your suggestions.

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• JUnit confusion: use 'extend Testcase' or '@Test' ?

  - by Rabarberski

  I've found the proper use (or at least the documentation) of JUnit very confusing. This question serves both as a future reference and as a real question. If I've understood correctly, there are two main approaches to create and run a JUnit test: Approach A: create a class that extends TestCase, and start test methods with the word test. When running the class as a JUnit Test (in Eclipse), all methods starting with the word test are automatically run. import junit.framework.TestCase; public class DummyTestA extends TestCase { public void testSum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Approach B: create a 'normal' class and prepend a @Test annotation to the method. Note that you do NOT have to start the method with the word test. import org.junit.*; import static org.junit.Assert.*; public class DummyTestB { @Test public void Sum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Mixing the two seems not to be a good idea, see e.g. this stackoverflow question: Now, my questions(s): What is the preferred approach, or when would you use one instead of the other? Approach B allows for testing for exceptions by extending the @Test annotation like in @Test(expected = ArithmeticException.class). But how do you test for exceptions when using approach A? When using approach A, you can group a number of test classes in a test suite. TestSuite suite = new TestSuite("All tests");<br/> suite.addTestSuite(DummyTestA.class); suite.addTestSuite(DummyTestAbis.class);` But this can't be used with approach B (since each testclass should subclass TestCase). What is the proper way to group tests for approach B?

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• Android - Basic CRUD (REST/RPC client) to remote server

  - by bsreekanth

  There are lot of discussion about REST client implementation in android, based on the talk at GoogleIO 2010, by Virgil Dobjanschi. My requirement may not necessarily involved, as I have some freedom to choose the configuration. I only target tablets configuration changes can be prevented if no other easy way (fix at Landscape mode etc) I am trying to achieve. Basic CRUD operation to my server (JSON RPC/ REST). Basically mimic an ajax request from android app (no webview, need native app) Based on the above mentioned talk, and some reading I see these options. Implement any of the 3 mentioned in the Google IO talk Especially, the last pattern may be more suitable as I don't care much of caching. But not sure how "real time" is sync implementation. Use HTTP request in AsyncTask. Simplest, but need to avoid re-sending request during change in device configuration (orientation change etc). Even if I fix at one orientation, recreation of activity still happens. So need to handle it elegantly. Use service to handle http request. So far, it say use service for long ruiing request. Not sure whether it is a good approach for simple GET/POST/PUt requests. Please share your experience on what could be the best way.

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• wsgi django not working

  - by MaKo

  im installing django, the test for wsgi is ok, but when i point my default file to the django test, it doesnt work, this is the test that works fine: default: /etc/apache2/sites-available/default <VirtualHost *:80> ServerName www.example.com ServerAlias example.com ServerAdmin [email protected] DocumentRoot /var/www <Directory /var/www/documents> Order allow,deny Allow from all </Directory> WSGIScriptAlias / /home/ubuntu/djangoProj/micopiloto/application.wsgi <Directory /home/ubuntu/djangoProj/mysitio/wsgi_handler.py> Order allow,deny Allow from all </Directory> </VirtualHost> application.wsgi:: ~/djangoProj/micopiloto import os import sys sys.path.append('/srv/www/cucus/application') os.environ['PYTHON_EGG_CACHE'] = '/srv/www/cucus/.python-egg' def application(environ, start_response): status = '200 OK' output = 'Hello World!MK SS9 tkt kkk' response_headers = [('Content-type', 'text/plain'), ('Content-Length', str(len(output)))] start_response(status, response_headers) return [output] but if I change the default to point to application_sa.wsgi the django test, it doesnt work :( application_sa.wsgi import os, sys sys.path.append('/home/ubuntu/djangoProj/micopiloto') os.environ['DJANGO_SETTINGS_MODULE'] = 'micopiloto.settings' import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler() I restart the apache server every time i change the wsgi to test, so what im i missing? thanks a lot!

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• What is a good approach to preloading data?

  - by Bob Horn

  Are there best practices out there for loading data into a database, to be used with a new installation of an application? For example, for application foo to run, it needs some basic data before it can even be started. I've used a couple options in the past: TSQL for every row that needs to be preloaded: IF NOT EXISTS (SELECT * FROM Master.Site WHERE Name = @SiteName) INSERT INTO [Master].[Site] ([EnterpriseID], [Name], [LastModifiedTime], [LastModifiedUser]) VALUES (@EnterpriseId, @SiteName, GETDATE(), @LastModifiedUser) Another option is a spreadsheet. Each tab represents a table, and data is entered into the spreadsheet as we realize we need it. Then, a program can read this spreadsheet and populate the DB. There are complicating factors, including the relationships between tables. So, it's not as simple as loading tables by themselves. For example, if we create Security.Member rows, then we want to add those members to Security.Role, we need a way of maintaining that relationship. Another factor is that not all databases will be missing this data. Some locations will already have most of the data, and others (that may be new locations around the world), will start from scratch. Any ideas are appreciated.

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• Database schemas WAY out of sync - need to get up to date without losing data

  - by Zind

  The problem: we have one application that has a portion which is used by a very small subset of the total users, and that part of the application is running off of a separate database as well. In a perfect world, the schemas of the two databases would be synced up, but such is not the case. Some migrations have been run on the smaller database, most haven't; and furthermore, there is nothing such as revision number to be able to easily identify which have and which haven't. We would like to solve this quandary for future projects. During a discussion we've come up with the following possible plan of action, and I am wondering if anyone knows of any project which has already solved this problem: What we would like to do is create an empty database from the schema of the large fully-migrated database, and then move all of the data from the smaller non-migrated database into that empty one. If it makes things easier, it can probably be assumed for the sake of this problem specifically that no migrations have ever removed anything, only added. Else, if there are other known solutions, I'd like to hear them as well.

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• Dynamic Control loading at wrong time?

  - by Telos

  This one is a little... odd. Basically I have a form I'm building using ASP.NET Dynamic Data, which is going to utilize several custom field templates. I've just added another field to the FormView, with it's own custom template, and the form is loading that control twice for no apparent reason. Worse yet, the first time it loads the template, the Row is not ready yet and I get the error message: {"Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control."} I'm accessing the Row variable in a LinqDataSource OnSelected event in order to get the child object... Now for the wierd part: If I reorder the fields a little, the one causing the problem no longer gets loaded twice. Any thoughts? EDIT: I've noticed that Page_Load gets called on the first load (when Row throws an exception if you try to use it) but does NOT get called the second time around. If that helps any... Right now managing it by just catching and ignoring the exception, but still a little worried that things will break if I don't find the real cause. EDIT 2: I've traced the problem to using FindControl recursively to find other controls on the page. Apparently FindControl can cause the page lifecycle events (at least up to page_load) to fire... and this occurs before that page "should" be loading so it's dynamic data "stuff" isn't ready yet.

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• What does this structure actually do?

  - by LGTrader

  I found this structure code in a Julia Set example from a book on CUDA. I'm a newbie C programmer and cannot get my head around what it's doing, nor have I found the right thing to read on the web to clear it up. Here's the structure: struct cuComplex { float r; float i; cuComplex( float a, float b ) : r(a), i(b) {} float magnitude2( void ) { return r * r + i * i; } cuComplex operator*(const cuComplex& a) { return cuComplex(r*a.r - i*a.i, i*a.r + r*a.i); } cuComplex operator+(const cuComplex& a) { return cuComplex(r+a.r, i+a.i); } }; and it's called very simply like this: cuComplex c(-0.8, 0.156); cuComplex a(jx, jy); int i = 0; for (i=0; i<200; i++) { a = a * a + c; if (a.magnitude2() > 1000) return 0; } return 1; So, the code did what? Defined something of structure type 'cuComplex' giving the real and imaginary parts of a number. (-0.8 & 0.156) What is getting returned? (Or placed in the structure?) How do I work through the logic of the operator stuff in the struct to understand what is actually calculated and held there? I think that it's probably doing recursive calls back into the stucture float magnitude2 (void) { return return r * r + i * i; } probably calls the '*' operator for r and again for i, and then the results of those two operations call the '+' operator? Is this correct and what gets returned at each step? Just plain confused. Thanks!

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• How can a link within a WebView load another layout using javascript?

  - by huffmaster

  So I have 2 layout files (main.xml, featured.xml) and both each have a single WebView. When the application starts "main.xml" loads a html file into it's WebView. In this html file I have a link that calls javascript that runs code in the Activity that loaded the html. Once back in this Activity code though I try running setContentView(R.layout.featured) but it just bombs out on me. If I debug it just dies without any real error and if I run it the application just Force closes. Am I going about this correctly or should I be doing something differently? final private int MAIN = 1; final private int FEATURED = 2; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); webview = (WebView) findViewById(R.id.wvMain); webview.getSettings().setJavaScriptEnabled(true); webview.getSettings().setSupportZoom(false); webview.addJavascriptInterface(new EHJavaScriptInterface(), "eh"); webview.loadUrl("file:///android_asset/default.html"); } final class EHJavaScriptInterface { EHJavaScriptInterface() { } public void loadLayout(final String lo) { int i = Integer.parseInt(lo.trim()); switch (i) { /****** THIS IS WHERE I'M BOMBING OUT *********/ case FEATURED: setContentView(R.layout.featured);break; case MAIN: setContentView(R.layout.main);break; } } }

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• Predicate crashing iPhone App!

  - by DVG

  To preface, this is a follow up to an inquiry made a few days ago: http://stackoverflow.com/questions/2981803/iphone-app-crashes-when-merging-managed-object-contexts Short Version: EXC_BAD_ACCESS is crashing my app, and zombie-mode revealed the culprit to be my predicate embedded within the fetch request embedded in my Fetched Results Controller. How does an object within an object get released without an explicit command to do so? Long Version: Application Structure Platforms View Controller - Games View Controller (Predicated upon platform selection) - Add Game View Controller When a row gets clicked on the Platforms view, it sets an instance variable in Games View for that platform, then the Games Fetched Results Controller builds a fetch request in the normal way: - (NSFetchedResultsController *)fetchedResultsController{ if (fetchedResultsController != nil) { return fetchedResultsController; } //build the fetch request for Games NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Game" inManagedObjectContext:context]; [request setEntity:entity]; //predicate NSPredicate *predicate = [NSPredicate predicateWithFormat:@"platform == %@", selectedPlatform]; [request setPredicate:predicate]; //sort based on name NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; //fetch and build fetched results controller NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:context sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; [sortDescriptor release]; [sortDescriptors release]; [predicate release]; [request release]; [aFetchedResultsController release]; return fetchedResultsController; } At the end of this method, the fetchedResultsController's _fetch_request - _predicate member is set to an NSComparisonPredicate object. All is well in the world. By the time - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section gets called, the _predicate is now a Zombie, which will eventually crash the application when the table attempts to update itself. I'm more or less flummoxed. I'm not releasing the fetched results controller or any of it's parts, and the only part getting dealloc'd is the predicate. Any ideas?

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• What is wrong with accessing DBI directly?

  - by canavanin

  Hi everyone! I'm currently reading Effective Perl Programming (2nd edition). I have come across a piece of code which was described as being poorly written, but I don't yet understand what's so bad about it, or how it should be improved. It would be great if someone could explain the matter to me. Here's the code in question: sub sum_values_per_key { my ( $class, $dsn, $user, $password, $parameters ) = @_; my %results; my $dbh = DBI->connect( $dsn, $user, $password, $parameters ); my $sth = $dbh->prepare( 'select key, calculate(value) from my_table'); $sth->execute(); # ... fill %results ... $sth->finish(); $dbh->disconnect(); return \%results; } The example comes from the chapter on testing your code (p. 324/325). The sentence that has left me wondering about how to improve the code is the following: Since the code was poorly written and accesses DBI directly, you'll have to create a fake DBI object to stand in for the real thing. I have probably not understood a lot of what the book has so far been trying to teach me, or I have skipped the section relevant for understanding what's bad practice about the above code... Well, thanks in advance for your help!

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