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• How do I install the OpenSSL C++ library on Ubuntu?

  - by Daryl Spitzer

  I'm trying to build some code on Ubuntu 10.04 LTS that uses OpenSSL 1.0.0. When I run make, it invokes g++ with the "-lssl" option. The source includes: #include <openssl/bio.h> #include <openssl/buffer.h> #include <openssl/des.h> #include <openssl/evp.h> #include <openssl/pem.h> #include <openssl/rsa.h> I ran: $ sudo apt-get install openssl Reading package lists... Done Building dependency tree Reading state information... Done openssl is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded. But I guess the openssl package doesn't include the library. I get these errors on make: foo.cpp:21:25: error: openssl/bio.h: No such file or directory foo.cpp:22:28: error: openssl/buffer.h: No such file or directory foo.cpp:23:25: error: openssl/des.h: No such file or directory foo.cpp:24:25: error: openssl/evp.h: No such file or directory foo.cpp:25:25: error: openssl/pem.h: No such file or directory foo.cpp:26:25: error: openssl/rsa.h: No such file or directory How do I install the OpenSSL C++ library on Ubuntu 10.04 LTS? I did a man g++ and (under "Options for Linking") for the -l option it states: " The linker searches a standard list of directories for the library..." and "The directories searched include several standard system directories..." What are those standard system directories?

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• ploting 3d graph in matlab?

  - by lytheone

  Hello, I am currently a begineer, and i am using matlab to do a data analysis. I have a a text file with data at the first row is formatted as follow: time;wave height 1;wave height 2;....... I have column until wave height 19 and rows total 4000 rows. Data in the first column is time in second. From 2nd column onwards, it is wave height elevation which is in meter. At the moment I like to ask matlab to plot a 3d graph with time on the x axis, wave elevation on the y axis, and wave elevation that correspond to wave height number from 1 to 19, i.e. data in column 2 row 10 has a let say 8m which is correspond to wave height 1 and time at the column 1 row 10. I have try the following: clear; filename='abc.daf'; path='C:\D'; a=dlmread([path '\' filename],' ', 2, 1); [nrows,ncols]=size(a); t=a(1:nrows,1);%define t from text file for i=(1:20), j=(2:21); end wi=a(:,j); for k=(2:4000), l=k; end r=a(l,:); But everytime i use try to plot them, the for loop wi works fine, but for r=a(l,:);, the plot only either give me the last time data only but i want all data in the file to be plot. Is there a way i can do that. I am sorry as it is a bit confusing but i will be very thankful if anyone can help me out. Thank you!!!!!!!!!!

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• Can the Singleton be replaced by Factory?

  - by lostiniceland

  Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

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• Grails XOM linkageerror - SAXParserException

  - by Stefan Kendall

  Possibly related: http://stackoverflow.com/questions/2762439/grails-attempting-to-include-htppbuilder-linkage-error I'm trying to include XOM in my grails project. How do I know which dependency library I need to exclude? I'm lost here. dependencies { build('xom:xom:1.1') { excludes "xml-apis" } } Error: java.lang.LinkageError: loader constraint violation: loader (instance of <bootloader>) previously initiated loading for a different type with name "org/xml/sax/SAXParseException" at java.lang.Class.getDeclaredMethods0(Native Method) at java.lang.Class.privateGetDeclaredMethods(Class.java:2427) at java.lang.Class.getDeclaredMethods(Class.java:1791) at java.security.AccessController.doPrivileged(Native Method) at org.codehaus.groovy.util.LazyReference.getLocked(LazyReference.java:33) at org.codehaus.groovy.util.LazyReference.get(LazyReference.java:20) at grails.util.PluginBuildSettings.getPluginInfos(PluginBuildSettings.groovy:124) at grails.util.PluginBuildSettings.getPluginInfos(PluginBuildSettings.groovy) at grails.util.PluginBuildSettings$getPluginInfos.callCurrent(Unknown Source) at grails.util.PluginBuildSettings.getPluginInfo(PluginBuildSettings.groovy:160) at grails.util.PluginBuildSettings$getPluginInfo.callCurrent(Unknown Source) at grails.util.PluginBuildSettings.getPluginInfoForSource(PluginBuildSettings.groovy:195) at org.codehaus.groovy.transform.ASTTransformationVisitor$3.call(ASTTransformationVisitor.java:303) at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:820) at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:513) at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:489) at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:466) at _GrailsEvents_groovy.run(_GrailsEvents_groovy:54) at _GrailsEvents_groovy$run.call(Unknown Source) at _GrailsArgParsing_groovy$run.call(Unknown Source) at _GrailsArgParsing_groovy.run(_GrailsArgParsing_groovy:29) at _GrailsArgParsing_groovy$run.call(Unknown Source) at _GrailsInit_groovy$run.call(Unknown Source) at _GrailsInit_groovy.run(_GrailsInit_groovy:38) at _GrailsInit_groovy$run.call(Unknown Source) at Help_.run(Help_.groovy:27) at Help_$run.call(Unknown Source) at gant.Gant.processTargets(Gant.groovy:494) at gant.Gant.processTargets(Gant.groovy:480)

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• How do I pass parameters between request-scoped beans

  - by smayers81

  This is a question that has been bothering me for sometime. My application uses ICEFaces for our UI framework and Spring 2.5 for Dependency Injection. In addition, Spring actually maintains all of our backing beans, not the ICEFaces framework, so our faces-config is basically empty. Navigation is not even really handled through navigation-rules. We perform manual redirects to new windows using window.open. All of our beans are defined in our appContext file as being request-scoped. I have Page ABC which is backed by BackingBeanABC. Inside that backing bean, I have a parameter say: private Order order; I then have Page XYZ backed by BackingBeanXYZ. When I redirect from page ABC to page XYZ, I want to transfer the 'order' property from ABC to XYZ. The problem is since everything is request-scoped and I'm performing a redirect, I am losing the value of 'description'. There has got to be an easier way to pass objects between beans in request scope during a redirect. Can anyone assist with this issue?

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• Algorithm(s) for rearranging simple symbolic algebraic expressions

  - by Gabe Johnson

  Hi, I would like to know if there is a straightforward algorithm for rearranging simple symbolic algebraic expressions. Ideally I would like to be able to rewrite any such expression with one variable alone on the left hand side. For example, given the input: m = (x + y) / 2 ... I would like to be able to ask about x in terms of m and y, or y in terms of x and m, and get these: x = 2*m - y y = 2*m - x Of course we've all done this algorithm on paper for years. But I was wondering if there was a name for it. It seems simple enough but if somebody has already cataloged the various "gotchas" it would make life easier. For my purposes I won't need it to handle quadratics. (And yes, CAS systems do this, and yes I know I could just use them as a library. I would like to avoid such a dependency in my application. I really would just like to know if there are named algorithms for approaching this problem.)

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• How to identify ideas and concepts in a given text

  - by Nick

  I'm working on a project at the moment where it would be really useful to be able to detect when a certain topic/idea is mentioned in a body of text. For instance, if the text contained: Maybe if you tell me a little more about who Mr Balzac is, that would help. It would also be useful if I could have a description of his appearance, or even better a photograph? It'd be great to be able to detect that the person has asked for a photograph of Mr Balzac. I could take a really naïve approach and just look for the word "photo" or "photograph", but this would obviously be no good if they wrote something like: Please, never send me a photo of Mr Balzac. Does anyone know where to start with this? Is it even possible? I've looked into things like nltk, but I've yet to find an example of someone doing something similar and am still not entirely sure what this kind of analysis is called. Any help that can get me off the ground would be great. Thanks!

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• How does CDI injection work in MDBs and @Scheduled beans?

  - by Nils-Petter Nilsen

  I'm working on a large Java EE 6 application that is deployed on JBoss 6 Final. My current tasks involve using @Inject consistently instead of @EJB, but I'm running into some problems on some types of beans, specifically @MessageDriven beans and beans with @Scheduled methods. What happens is that if I'm unlucky with the timing (for @Schedule) or if there are messages in the MDBs' queues at startup, instantiation of the beans will fail because the injected resources (which are EJBs themselves) are not bound yet. Because I use @Inject, I'm guessing that the EJB container considers my beans to be ready, since the container itself does not care about @Inject; it probably simply assumes that since there are no @EJB injections, the beans are ready for use. The injected CDI proxies will then fail because the resources to inject aren't actually bound yet. Tiny example: @Stateless @LocalBean public class MySupportingBean { public void doSomething() { ... } } @Singleton public class MyScheduledBean { @Inject private MySupportingBean supportingBean; @Schedule(second = "*/1", hour = "*", minute = "*", persistent = false) public void onTimeout() { supportingBean.doSomething(); } } The above example will probably not fail often because there are only two beans, but the project I'm working on binds lots of EJBs, which will amplify the problem. But it might fail because there is no guarantee that MySupportingBean is bound first, and if onTimeout is invoked before MySupportingBean is bound, then instantiation of MyScheduledBean will fail. If I used @EJB instead, MyScheduledBean wouldn't be bound until the dependency to MySupportingBean was satisfied. Note that the example will not fail in onTimeout itself, but when CDI attempts to inject MySupportingBean. I've read a lot of posts on different forums where many people argue that @Inject is always better. Generally, I agree, but how do they handle @Schedule or @MessageDriven combined with @Inject? In my experience, it comes down to dumb luck whether the beans will work or not in those cases, and the beans will fail arbitrarily, depending on which order the EJBs are deployed in, and when @Schedule or onMessage are invoked.

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• Did the Unity Team fix that "generics handling" bug back in 2008?

  - by rasx

  At my level of experience with Unity it might be faster to ask whether the "generics handling" bug acknowledged by ctavares back in 2008 was fixed in a public release. Here was the problem (which might be my problem today): Hi, I get an exception when using .... container.RegisterType(typeof(IDictionary<,), typeof(Dictionary<,)); The exception is... "Resolution of the dependency failed, type = \"IDictionary2\", name = \"\". Exception message is: The current build operation (build key Build Key[System.Collections.Generic.Dictionary2[System.String,System.String], null]) failed: The current build operation (build key Build Key[System.Collections.Generic.Dictionary2[System.String,System.String], null]) failed: The type Dictionary2 has multiple constructors of length 2. Unable to disambiguate. When I attempt... IDictionary myExampleDictionary = container.Resolve(); Here was the moderated response: There are no books that'll help, Unity is a little too new for publishers to have caught up yet. Unfortunately, you've run into a bug in our generics handling. This is currently fixed in our internal version, but it'll be a little while before we can get the bits out. In the meantime, as a workaround you could do something like this instead: public class WorkaroundDictionary : Dictionary { public WorkaroundDictionary() { } } container.RegisterType(typeof(IDictionary<,),typeof(WorkaroundDictionary<,)); The WorkaroundDictionary only has the default constructor so it'll inject no problem. Since the rest of your app is written in terms of IDictionary, when we get the fixed version done you can just replace the registration with the real Dictionary class, throw out the workaround, and everything will still just work. Sorry about the bug, it'll be fixed soon!

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• Why does Hibernate ignore the JPA2 standardized properties in my persistence.xml?

  - by Ophidian

  I have an extremely simple web application running in Tomcat using Spring 3.0.1, Hibernate 3.5.1, JPA 2, and Derby. I am defining all of my database connectivity in persistence.xml and merely using Spring for dependency injection. I am using embedded Derby as my database. Everything works correctly when I define the driver and url properties in persistence.xml in the classic Hibernate manner as thus: <property name="hibernate.connection.driver_class" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="hibernate.connection.url" value="jdbc:derby:webdb;create=true"/> The problems occur when I switch my configuration to the JPA2 standardized properties as thus: <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="javax.persistence.jdbc.url" value="jdbc:derby:webdb;create=true"/> When using the JPA2 property keys, the application bails hard with the following exception: java.lang.UnsupportedOperationException: The user must supply a JDBC connection Does anyone know why this is failing? NOTE: I have copied the javax... property strings straight from the Hibernate reference documentation, so a typo is extremely unlikely.

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• What is a good programming language/environment for Linux database applications?

  - by Dkellygb

  I could use some advice on my move from the Windows world to Linux. For my business, I have used VB6 and Microsoft Access with both Access databases and SQL server in the past. The easy to use forms, report writers and programming language were perfect for CRUD apps and analysis for our small hotel/restaurant business. After using Linux at home for some time I would like to convert our small business. Our server is already a Linux box using Samba. I am happy with the OpenOffice.org applications instead of Microsoft Office. The only thing which is holding me back is a desktop database application where I can develop the forms and reports we require. Base does not seem to be up to the job yet from my experience. I would like something like VB.Net with visual studio (express) but I would like to avoid Mono – I just don’t see the point of it. (You can correct me if I’m wrong.) But a good collection of forms, controls and a good report writer would be ideal. I have looked at web based stuff like Ruby on Rails, but I think a webserver for our 5 pc network is overkill. I don’t mind running a proper database on our Ubuntu 9.10 server. I may have exposed a few prejudices above but my mind is open. Any thoughts?

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• Handling missing/incomplete data in R--is there function to mask but not remove NAs?

  - by doug

  As you would expect from a DSL aimed at data analysis, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs: mean( c(5,6,12,87,9,NA,43,67), na.rm=T) But if you want to deal with NAs before the function call, you need to do something like this: to remove each 'NA' from a vector: vx = vx[!is.na(a)] to remove each 'NA' from a vector and replace it w/ a '0': ifelse(is.na(vx), 0, vx) to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions permanently remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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• Subscribe to the Button's events into a custom control

  - by ThitoO

  Do you know how can I subscribe to an event of the base of my customControl ? I've a custom control with some dependency properties : public class MyCustomControl : Button { static MyCustomControl () { DefaultStyleKeyProperty.OverrideMetadata( typeof( MyCustomControl ), new FrameworkPropertyMetadata( typeof( MyCustomControl ) ) ); } public ICommand KeyDownCommand { get { return (ICommand)GetValue( KeyDownCommandProperty ); } set { SetValue( KeyDownCommandProperty, value ); } } public static readonly DependencyProperty KeyDownCommandProperty = DependencyProperty.Register( "KeyDownCommand", typeof( ICommand ), typeof( MyCustomControl ) ); public ICommand KeyUpCommand { get { return (ICommand)GetValue( KeyUpCommandProperty ); } set { SetValue( KeyUpCommandProperty, value ); } } public static readonly DependencyProperty KeyUpCommandProperty = DependencyProperty.Register( "KeyUpCommand", typeof( ICommand ), typeof( MyCustomControl ) ); public ICommand KeyPressedCommand { get { return (ICommand)GetValue( KeyPressedCommandProperty ); } set { SetValue( KeyPressedCommandProperty, value ); } } public static readonly DependencyProperty KeyPressedCommandProperty = DependencyProperty.Register( "KeyPressedCommand", typeof( ICommand ), typeof( MyCustomControl ) ); } And I whant to subscribe to Button's events (like MouseLeftButtonDown) to run some code in my customControl. Do you know how can I do something like this in the constructor ? static MyCustomControl() { DefaultStyleKeyProperty.OverrideMetadata( typeof( MyCustomControl ), new FrameworkPropertyMetadata( typeof( MyCustomControl ) ) ); MouseLeftButtonDownEvent += (object sender, MouseButtonEventArgs e) => "something"; } Thanks for you help

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• How to manage multiple python versions ?

  - by Gyom

  short version: how can I get rid of the multiple-versions-of-python nightmare ? long version: over the years, I've used several versions of python, and what is worse, several extensions to python (e.g. pygame, pylab, wxPython...). Each time it was on a different setup, with different OSes, sometimes different architectures (like my old PowerPC mac). Nowadays I'm using a mac (OSX 10.6 on x86-64) and it's a dependency nightmare each time I want to revive script older than a few months. Python itself already comes in three different flavours in /usr/bin (2.5, 2.6, 3.1), but I had to install 2.4 from macports for pygame, something else (cannot remember what) forced me to install all three others from macports as well, so at the end of the day I'm the happy owner of seven (!) instances of python on my system. But that's not the problem, the problem is, none of them has the right (i.e. same set of) libraries installed, some of them are 32bits, some 64bits, and now I'm pretty much lost. For example right now I'm trying to run a three-year-old script (not written by me) which used to use matplotlib/numpy to draw a real-time plot within a rectangle of a wxwidgets window. But I'm failing miserably: py26-wxpython from macports won't install, stock python has wxwidgets included but also has some conflict between 32 bits and 64 bits, and it doesn't have numpy... what a mess ! Obviously, I'm doing things the wrong way. How do you usally cope with all that chaos ?e

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• Reconstructing trees from a "fingerprint"

  - by awshepard

  I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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• MySQL table data transformation -- how can I dis-aggreate MySQL time data?

  - by lighthouse65

  We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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• Loading Native library to external Package in Eclipse not working. is it a Bug?

  - by TacB0sS

  I was about to report a but to Eclipse, but I was thinking to give this a chance here first: If I add an external package, the application cannot find the referenced native library, except in the case specified at the below: If my workspace consists of a single project, and I import an external package 'EX_package.jar' from a folder outside of the project folder, I can assign a folder to the native library location via: mouse over package - right click - properties - Native Library - Enter your folder. This does not work. In runtime the application does not load the library, System.mapLibraryName(Path) also does not work. Further more, if I create a User Library, and add the package to it and define a folder for the native library it still does not. If it works for you then I have a major bug since it does not work on my computer I test this in any combination I could think of, including adding the path to the windows PATH parameter, and so many other ways I can't even start to remember, nothing worked, I played with this for hours and had a colleague try to assist me, but we both came up empty. Further more, if I have a main project that is dependent on few other projects in my workspace, and they all need to use the same 'EX_package.jar' I MUST supply a HARD COPY INTO EACH OF THEM, it will ONLY (I can't stress the ONLYNESS, I got freaked out by this) work if I have a hard copy of the package in ALL of the project folders that the main project has a dependency on, and ONLY if I configure the Native path in each of them!! This also didn't do the trick. please tell me there is a solution to this, this drives me nuts... Thanks, Adam Zehavi.

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• Asymptotic runtime of list-to-tree function

  - by Deestan

  I have a merge function which takes time O(log n) to combine two trees into one, and a listToTree function which converts an initial list of elements to singleton trees and repeatedly calls merge on each successive pair of trees until only one tree remains. Function signatures and relevant implementations are as follows: merge :: Tree a -> Tree a -> Tree a --// O(log n) where n is size of input trees singleton :: a -> Tree a --// O(1) empty :: Tree a --// O(1) listToTree :: [a] -> Tree a --// Supposedly O(n) listToTree = listToTreeR . (map singleton) listToTreeR :: [Tree a] -> Tree a listToTreeR [] = empty listToTreeR (x:[]) = x listToTreeR xs = listToTreeR (mergePairs xs) mergePairs :: [Tree a] -> [Tree a] mergePairs [] = [] mergePairs (x:[]) = [x] mergePairs (x:y:xs) = merge x y : mergePairs xs This is a slightly simplified version of exercise 3.3 in Purely Functional Data Structures by Chris Okasaki. According to the exercise, I shall now show that listToTree takes O(n) time. Which I can't. :-( There are trivially ceil(log n) recursive calls to listToTreeR, meaning ceil(log n) calls to mergePairs. The running time of mergePairs is dependent on the length of the list, and the sizes of the trees. The length of the list is 2^h-1, and the sizes of the trees are log(n/(2^h)), where h=log n is the first recursive step, and h=1 is the last recursive step. Each call to mergePairs thus takes time (2^h-1) * log(n/(2^h)) I'm having trouble taking this analysis any further. Can anyone give me a hint in the right direction?

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• Unable to upgrade PEAR from 1.9.2 to 1.9.4

  - by user940768

  I am on a Ubuntu 11.10 and trying to upgrade from 1.9.2 to 1.9.4, but it simply don't work. Here are the commands I am following in sequence $ sudo apt-get install php-pear Reading package lists... Done Building dependency tree Reading state information... Done php-pear is already the newest version. The following packages were automatically installed and are no longer required: linux-headers-3.0.0-14-generic-pae libaccess-bridge-java-jni libaccess-bridge-java Use 'apt-get autoremove' to remove them. 0 upgraded, 0 newly installed, 0 to remove and 6 not upgraded. $ sudo pear channel-update pear.php.net Updating channel "pear.php.net" Channel "pear.php.net" is up to date $ sudo pear upgrade-all Nothing to upgrade-all $ sudo pear install –alldeps pear.phpunit.de/PHPUnit parsePackageName(): invalid package name "–alldeps" in "–alldeps" invalid package name/package file "–alldeps" Did not download optional dependencies: phpunit/PHP_Invoker, use --alldeps to download automatically phpunit/PHPUnit requires PEAR Installer (version >= 1.9.4), installed version is 1.9.2 phpunit/PHPUnit can optionally use package "phpunit/PHP_Invoker" (version >= 1.1.0) phpunit/Text_Template requires PEAR Installer (version >= 1.9.4), installed version is 1.9.2 phpunit/PHP_CodeCoverage requires PEAR Installer (version >= 1.9.4), installed version is 1.9.2 phpunit/PHP_CodeCoverage requires package "phpunit/Text_Template" (version >= 1.1.1) phpunit/PHP_CodeCoverage can optionally use PHP extension "xdebug" (version >= 2.0.5) phpunit/PHPUnit_MockObject requires PEAR Installer (version >= 1.9.4), installed version is 1.9.2 phpunit/PHPUnit_MockObject requires package "phpunit/Text_Template" (version >= 1.1.1) phpunit/PHP_TokenStream requires PEAR Installer (version >= 1.9.4), installed version is 1.9.2 No valid packages found install failed Any thoughts?

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• Injecting Dependencies into Domain Model classes with Nhibernate (ASP.NET MVC + IOC)

  - by Sunday Ironfoot

  I'm building an ASP.NET MVC application that uses a DDD (Domain Driven Design) approach with database access handled by NHibernate. I have domain model class (Administrator) that I want to inject a dependency into via an IOC Container such as Castle Windsor, something like this: public class Administrator { public virtual int Id { get; set; } //.. snip ..// public virtual string HashedPassword { get; protected set; } public void SetPassword(string plainTextPassword) { IHashingService hasher = IocContainer.Resolve<IHashingService>(); this.HashedPassword = hasher.Hash(plainTextPassword); } } I basically want to inject IHashingService for the SetPassword method without calling the IOC Container directly (because this is suppose to be an IOC Anti-pattern). But I'm not sure how to go about doing it. My Administrator object either gets instantiated via new Administrator(); or it gets loaded via NHibernate, so how would I inject the IHashingService into the Administrator class? On second thoughts, am I going about this the right way? I was hoping to avoid having my codebase littered with... currentAdmin.Password = HashUtils.Hash(password, Algorithm.Sha512); ...and instead get the domain model itself to take care of hashing and neatly encapsulate it away. I can envisage another developer accidently choosing the wrong algorithm and having some passwords as Sha512, and some as MD5, some with one salt, and some with a different salt etc. etc. Instead if developers are writing... currentAdmin.SetPassword(password); ...then that would hide those details away and take care of those problems listed above would it not?

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• What is the best way to use Guice and JMock together?

  - by Yishai

  I have started using Guice to do some dependency injection on a project, primarily because I need to inject mocks (using JMock currently) a layer away from the unit test, which makes manual injection very awkward. My question is what is the best approach for introducing a mock? What I currently have is to make a new module in the unit test that satisfies the dependencies and bind them with a provider that looks like this: public class JMockProvider<T> implements Provider<T> { private T mock; public JMockProvider(T mock) { this.mock = mock; } public T get() { return mock; } } Passing the mock in the constructor, so a JMock setup might look like this: final CommunicationQueue queue = context.mock(CommunicationQueue.class); final TransactionRollBack trans = context.mock(TransactionRollBack.class); Injector injector = Guice.createInjector(new AbstractModule() { @Override protected void configure() { bind(CommunicationQueue.class).toProvider(new JMockProvider<QuickBooksCommunicationQueue>(queue)); bind(TransactionRollBack.class).toProvider(new JMockProvider<TransactionRollBack>(trans)); } }); context.checking(new Expectations() {{ oneOf(queue).retrieve(with(any(int.class))); will(returnValue(null)); never(trans); }}); injector.getInstance(RunResponse.class).processResponseImpl(-1); Is there a better way? I know that AtUnit attempts to address this problem, although I'm missing how it auto-magically injects a mock that was created locally like the above, but I'm looking for either a compelling reason why AtUnit is the right answer here (other than its ability to change DI and mocking frameworks around without changing tests) or if there is a better solution to doing it by hand.

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• Generating easy-to-remember random identifiers

  - by Carl Seleborg

  Hi all, As all developers do, we constantly deal with some kind of identifiers as part of our daily work. Most of the time, it's about bugs or support tickets. Our software, upon detecting a bug, creates a package that has a name formatted from a timestamp and a version number, which is a cheap way of creating reasonably unique identifiers to avoid mixing packages up. Example: "Bug Report 20101214 174856 6.4b2". My brain just isn't that good at remembering numbers. What I would love to have is a simple way of generating alpha-numeric identifiers that are easy to remember. Examples would be "azil3", "ulmops", "fel2way", etc. I just made these up, but they are much easier to recognize when you see many of them at once. I know of algorithms that perform trigram analysis on text (say you feed them a whole book in German) and that can generate strings that look and feel like German words. This requires lots of data, though, and makes it slightly less suitable for embedding in an application just for this purpose. Do you know of anything else? Thanks! Carl

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• osx rvm ruby 1.8.7 nokogiri 1.4.1 - ERROR: Failed to build gem native extension.

  - by tommasop

  I'm stuck with this problem. cat ~/.rvm/gems/ruby-1.8.7-p249/gems/nokogiri-1.4.1/ext/nokogiri/mkmf.log Gives this errors (clipped) conftest.c:3: error: 'xmlParseDoc' undeclared (first use in this function) conftest.c:3: error: (Each undeclared identifier is reported only once conftest.c:3: error: for each function it appears in.) For several libraries which are found in the system. If I manually go into ~/.rvm/gems/ruby-1.8.7-p249/gems/nokogiri-1.4.1/ext/nokogiri/ And compile and install everything goes fine ruby extconf.rb make make install mkdir -p /Users/tommasop/.rvm/rubies/ruby-1.8.7-p249/lib/ruby/site_ruby/1.8/i686-darwin9.8.0/nokogiri /usr/bin/install -c -m 0755 nokogiri.bundle /Users/tommasop/.rvm/rubies/ruby-1.8.7-p249/lib/ruby/site_ruby/1.8/i686-darwin9.8.0/nokogiri except that on script/server: ? script/server --debugger => Booting Mongrel => Rails 2.3.5 application starting on http://0.0.0.0:3000 ./script/../config/../vendor/rails/railties/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be removed on or after August 2010. Use #requirement The following gems have native components that need to be built nokogiri You're running: ruby 1.8.7.249 at /Users/tommasop/.rvm/rubies/ruby-1.8.7-p249/bin/ruby rubygems 1.3.6 at /Users/tommasop/.rvm/gems/ruby-1.8.7-p249, /Users/tommasop/.rvm/gems/ruby-1.8.7-p249%global Run `rake gems:build` to build the unbuilt gems. Any help greatly appreciated!

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• Raw types and subtyping

  - by Dmitrii

  We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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