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  • Is Data Science “Science”?

    - by BuckWoody
    I hold the term “science” in very high esteem. I grew up on the Space Coast in Florida, and eventually worked at the Kennedy Space Center, surrounded by very intelligent people who worked in various scientific fields. Recently a new term has entered the computing dialog – “Data Scientist”. Since it’s not a standard term, it has a lot of definitions, and in fact has been disputed as a correct term. After all, the reasoning goes, if there’s no such thing as “Data Science” then how can there be a Data Scientist? This argument has been made before, albeit with a different term – “Computer Science”. In Peter Denning’s excellent article “Is Computer Science Science” (April  2005/Vol. 48, No. 4 COMMUNICATIONS OF THE ACM) there are many points that separate “science” from “engineering” and even “art”.  I won’t repeat the content of that article here (I recommend you read it on your own) but will leverage the points he makes there. Definition of Science To ask the question “is data science ‘science’” then we need to start with a definition of terms. Various references put the definition into the same basic areas: Study of the physical world Systematic and/or disciplined study of a subject area ...and then they include the things studied, the bodies of knowledge and so on. The word itself comes from Latin, and means merely “to know” or “to study to know”. Greek divides knowledge further into “truth” (episteme), and practical use or effects (tekhne). Normally computing falls into the second realm. Definition of Data Science And now a more controversial definition: Data Science. This term is so new and perhaps so niche that the major dictionaries haven’t yet picked it up (my OED reference is older – can’t afford to pop for the online registration at present). Researching the term's general use I created an amalgam of the definitions this way: “Studying and applying mathematical and other techniques to derive information from complex data sets.” Using this definition, data science certainly seems to be science - it's learning about and studying some object or area using systematic methods. But implicit within the definition is the word “application”, which makes the process more akin to engineering or even technology than science. In fact, I find that using these techniques – and data itself – part of science, not science itself. I leave out the concept of studying data patterns or algorithms as part of this discipline. That is actually a domain I see within research, mathematics or computer science. That of course is a type of science, but does not seek for practical applications. As part of the argument against calling it “Data Science”, some point to the scientific method of creating a hypothesis, testing with controls, testing results against the hypothesis, and documenting for repeatability.  These are not steps that we often take in working with data. We normally start with a question, and fit patterns and algorithms to predict outcomes and find correlations. In this way Data Science is more akin to statistics (and in fact makes heavy use of them) in the process rather than starting with an assumption and following on with it. So, is Data Science “Science”? I’m uncertain – and I’m uncertain it matters. Even if we are facing rampant “title inflation” these days (does anyone introduce themselves as a secretary or supervisor anymore?) I can tolerate the term at least from the intent that we use data to study problems across a wide spectrum, rather than restricting it to a single domain. And I also understand those who have worked hard to achieve the very honorable title of “scientist” who have issues with those who borrow the term without asking. What do you think? Science, or not? Does it matter?

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  • Solaris 11.2: Functional Deprecation

    - by alanc
    In Solaris 11.1, I updated the system headers to enable use of several attributes on functions, including noreturn and printf format, to give compilers and static analyzers more information about how they are used to give better warnings when building code. In Solaris 11.2, I've gone back in and added one more attribute to a number of functions in the system headers: __attribute__((__deprecated__)). This is used to warn people building software that they’re using function calls we recommend no longer be used. While in many cases the Solaris Binary Compatibility Guarantee means we won't ever remove these functions from the system libraries, we still want to discourage their use. I made passes through both the POSIX and C standards, and some of the Solaris architecture review cases to come up with an initial list which the Solaris architecture review committee accepted to start with. This set is by no means a complete list of Obsolete function interfaces, but should be a reasonable start at functions that are well documented as deprecated and seem useful to warn developers away from. More functions may be flagged in the future as they get deprecated, or if further passes are made through our existing deprecated functions to flag more of them. Header Interface Deprecated by Alternative Documented in <door.h> door_cred(3C) PSARC/2002/188 door_ucred(3C) door_cred(3C) <kvm.h> kvm_read(3KVM), kvm_write(3KVM) PSARC/1995/186 Functions on kvm_kread(3KVM) man page kvm_read(3KVM) <stdio.h> gets(3C) ISO C99 TC3 (Removed in ISO C11), POSIX:2008/XPG7/Unix08 fgets(3C) gets(3C) man page, and just about every gets(3C) reference online from the past 25 years, since the Morris worm proved bad things happen when it’s used. <unistd.h> vfork(2) PSARC/2004/760, POSIX:2001/XPG6/Unix03 (Removed in POSIX:2008/XPG7/Unix08) posix_spawn(3C) vfork(2) man page. <utmp.h> All functions from getutent(3C) man page PSARC/1999/103 utmpx functions from getutentx(3C) man page getutent(3C) man page <varargs.h> varargs.h version of va_list typedef ANSI/ISO C89 standard <stdarg.h> varargs(3EXT) <volmgt.h> All functions PSARC/2005/672 hal(5) API volmgt_check(3VOLMGT), etc. <sys/nvpair.h> nvlist_add_boolean(3NVPAIR), nvlist_lookup_boolean(3NVPAIR) PSARC/2003/587 nvlist_add_boolean_value, nvlist_lookup_boolean_value nvlist_add_boolean(3NVPAIR) & (9F), nvlist_lookup_boolean(3NVPAIR) & (9F). <sys/processor.h> gethomelgroup(3C) PSARC/2003/034 lgrp_home(3LGRP) gethomelgroup(3C) <sys/stat_impl.h> _fxstat, _xstat, _lxstat, _xmknod PSARC/2009/657 stat(2) old functions are undocumented remains of SVR3/COFF compatibility support If the above table is cut off when viewing in the blog, try viewing this standalone copy of the table. To See or Not To See To see these warnings, you will need to be building with either gcc (versions 3.4, 4.5, 4.7, & 4.8 are available in the 11.2 package repo), or with Oracle Solaris Studio 12.4 or later (which like Solaris 11.2, is currently in beta testing). For instance, take this oversimplified (and obviously buggy) implementation of the cat command: #include <stdio.h> int main(int argc, char **argv) { char buf[80]; while (gets(buf) != NULL) puts(buf); return 0; } Compiling it with the Studio 12.4 beta compiler will produce warnings such as: % cc -V cc: Sun C 5.13 SunOS_i386 Beta 2014/03/11 % cc gets_test.c "gets_test.c", line 6: warning: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 The exact warning given varies by compilers, and the compilers also have a variety of flags to either raise the warnings to errors, or silence them. Of couse, the exact form of the output is Not An Interface that can be relied on for automated parsing, just shown for example. gets(3C) is actually a special case — as noted above, it is no longer part of the C Standard Library in the C11 standard, so when compiling in C11 mode (i.e. when __STDC_VERSION__ >= 201112L), the <stdio.h> header will not provide a prototype for it, causing the compiler to complain it is unknown: % gcc -std=c11 gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: implicit declaration of function ‘gets’ [-Wimplicit-function-declaration] while (gets(buf) != NULL) ^ The gets(3C) function of course is still in libc, so if you ignore the error or provide your own prototype, you can still build code that calls it, you just have to acknowledge you’re taking on the risk of doing so yourself. Solaris Studio 12.4 Beta % cc gets_test.c "gets_test.c", line 6: warning: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 % cc -errwarn=E_DEPRECATED_ATT gets_test.c "gets_test.c", line 6: "gets" is deprecated, declared in : "/usr/include/iso/stdio_iso.h", line 221 cc: acomp failed for gets_test.c This warning is silenced in the 12.4 beta by cc -erroff=E_DEPRECATED_ATT No warning is currently issued by Studio 12.3 & earler releases. gcc 3.4.3 % /usr/sfw/bin/gcc gets_test.c gets_test.c: In function `main': gets_test.c:6: warning: `gets' is deprecated (declared at /usr/include/iso/stdio_iso.h:221) Warning is completely silenced with gcc -Wno-deprecated-declarations gcc 4.7.3 % /usr/gcc/4.7/bin/gcc gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Wdeprecated-declarations] % /usr/gcc/4.7/bin/gcc -Werror=deprecated-declarations gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: error: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Werror=deprecated-declarations] cc1: some warnings being treated as errors Warning is completely silenced with gcc -Wno-deprecated-declarations gcc 4.8.2 % /usr/bin/gcc gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: warning: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Wdeprecated-declarations] while (gets(buf) != NULL) ^ % /usr/bin/gcc -Werror=deprecated-declarations gets_test.c gets_test.c: In function ‘main’: gets_test.c:6:5: error: ‘gets’ is deprecated (declared at /usr/include/iso/stdio_iso.h:221) [-Werror=deprecated-declarations] while (gets(buf) != NULL) ^ cc1: some warnings being treated as errors Warning is completely silenced with gcc -Wno-deprecated-declarations

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  • Application Composer: Exposing Your Customizations in BI Analytics and Reporting

    - by Richard Bingham
    Introduction This article explains in simple terms how to ensure the customizations and extensions you have made to your Fusion Applications are available for use in reporting and analytics. It also includes four embedded demo videos from our YouTube channel (if they don't appear check the browser address bar for a blocking shield icon). If you are new to Business Intelligence consider first reviewing our getting started article, and you can read more about the topic of custom subject areas in the documentation book Extending Sales. There are essentially four sections to this post. First we look at how custom fields added to standard objects are made available for reporting. Secondly we look at creating custom subject areas on the standard objects. Next we consider reporting on custom objects, starting with simple standalone objects, then child custom objects, and finally custom objects with relationships. Finally this article reviews how flexfields are exposed for reporting. Whilst this article applies to both Cloud/SaaS and on-premises deployments, if you are an on-premises developer then you can also use the BI Administration Tool to customize your BI metadata repository (the RPD) and create new subject areas. Whilst this is not covered here you can read more in Chapter 8 of the Extensibility Guide for Developers. Custom Fields on Standard Objects If you add a custom field to your standard object then it's likely you'll want to include it in your reports. This is very simple, since all new fields are instantly available in the "[objectName] Extension" folder in existing subject areas. The following two minute video demonstrates this. Custom Subject Areas for Standard Objects You can create your own subject areas for use in analytics and reporting via Application Composer. An example use-case could be to simplify the seeded subject areas, since they sometimes contain complex data fields and internal values that could confuse business users. One thing to note is that you cannot create subject areas in a sandbox, as it is not supported by BI, so once your custom object is tested and complete you'll need to publish the sandbox before moving forwards. The subject area creation processes is essentially two-fold. Once the request is submitted the ADF artifacts are generated, then secondly the related metadata is sent to the BI presentation server API's to make the updates there. One thing to note is that this second step may take up to ten minutes to complete. Once finished the status of the custom subject area request should show as 'OK' and it is then ready for use. Within the creation processes wizard-like steps there are three concepts worth highlighting: Date Flattening - this feature permits the roll up of reports at various date levels, such as data by week, month, quarter, or year. You simply check the box to enable it for that date field. Measures - these are your own functions that you can build into the custom subject area. They are related to the field data type and include min-max for dates, and sum(), avg(), and count() for  numeric fields. Implicit Facts - used to make the BI metadata join between your object fields and the calculated measure fields. The advice is to choose the most frequently used measure to ensure consistency. This video shows a simple example, where a simplified subject area is created for the customer 'Contact' standard object, picking just a few fields upon which users can then create reports. Custom Objects Custom subject areas support three types of custom objects. First is a simple standalone custom object and for which the same process mentioned above applies. The next is a custom child object created on a standard object parent, and finally a custom object that is related to a parent object - usually through a dynamic choice list. Whilst the steps in each of these last two are mostly the same, there are differences in the way you choose the objects and their fields. This is illustrated in the videos below.The first video shows the process for creating a custom subject area for a simple standalone custom object. This second video demonstrates how to create custom subject areas for custom objects that are of parent:child type, as well as those those with dynamic-choice-list relationships. &lt;span id=&quot;XinhaEditingPostion&quot;&gt;&lt;/span&gt; Flexfields Dynamic and Extensible Flexfields satisfy a similar requirement as custom fields (for Application Composer), with flexfields common across the Fusion Financials, Supply Chain and Procurement, and HCM applications. The basic principle is when you enable and configure your flexfields, in the edit page under each segment region (for both global and context segments) there is a BI Enabled check box. Once this is checked and you've completed your configuration, you run the Scheduled Process job named 'Import Oracle Fusion Data Extensions for Transactional Business Intelligence' to generate and migrate the related BI artifacts and data. This applies for dynamic, key, and extensible flexfields. Of course there is more to consider in terms of how you wish your flexfields to be implemented and exposed in your reports, and details are given in Chapter 4 of the Extending Applications guide.

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  • SSRS Report from Oracle DB - Use stored procedure

    - by Emtucifor
    I am developing a report in Sql Server Reporting Services 2005, connecting to an Oracle 11g database. As you post replies perhaps it will help to know that I'm skilled in MSSQL Server and inexperienced in Oracle. I have multiple nested subreports and need to use summary data in outer reports and the same data but in detail in the inner reports. In order to spare the DB server from multiple executions, I thought to populate some temp tables at the beginning and then query just them the multiple times in the report and the subreports. In SSRS, Datasets are evidently executed in the order they appear in the RDL file. And you can have a dataset that doesn't return a rowset. So I created a stored procedure to populate my four temp tables and made this the first Dataset in my report. This SP works when I run it from SQLDeveloper and I can query the data from the temp tables. However, this didn't appear to work out because SSRS was apparently not reusing the same session, so even though the global temporary tables were created with ON COMMIT PRESERVE ROWS my Datasets were empty. I switched to using "real" tables and am now passing in an additional parameter, a GUID in string form, uniquely generated on each new execution, that is part of the primary key of each table, so I can get back just the rows for this execution. Running this from Sql Developer works fine, example: DECLARE ActivityCode varchar2(15) := '1208-0916 '; ExecutionID varchar2(32) := SYS_GUID(); BEGIN CIPProjectBudget (ActivityCode, ExecutionID); END; Never mind that in this example I don't know the GUID, this simply proves it works because rows are inserted to my four tables. But in the SSRS report, I'm still getting no rows in my Datasets and SQL Developer confirms no rows are being inserted. So I'm thinking along the lines of: Oracle uses implicit transactions and my changes aren't getting committed? Even though I can prove that the non-rowset returning SP is executing (because if I leave out the parameter mapping it complains at report rendering time about not having enough parameters) perhaps it's not really executing. Somehow. Wrong execution order isn't the problem or rows would appear in the tables, and they aren't. I'm interested in any ideas about how to accomplish this (especially the part about not running the main queries multiple times). I'll redesign my whole report. I'll stop using a stored procedure. Suggest anything you like! I just need help getting this working and I am stuck. If you want more details, in my SSRS report I have a List object (it's a container that repeats once for each row in a Dataset) that has some header values and then contains a subreport. Eventually, there will be four total reports: one main report, with three nested subreports. Each subreport will be in a List on the parent report.

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  • Eventlet or gevent or Stackless + Twisted, Pylons, Django and SQL Alchemy

    - by Khorkrak
    We're using Twisted extensively for apps requiring a great deal of asynchronous io. There are some cases where stuff is cpu bound instead and for that we spawn a pool of processes to do the work and have a system for managing these across multiple servers as well - all done in Twisted. Works great. The problem is that it's hard to bring new team members up to speed. Writing asynchronous code in Twisted requires a near vertical learning curve. It's as if humans just don't think that way naturally. We're considering a mixed approach perhaps. Maybe do the xmlrpc server part and process management in Twisted still but the other stuff in code that at least looks synchronous while not being as such. Then again I like explicit over implicit so hmmm. Anyway onto greenlets - how well does that stuff work? So there's Stackless and as you can see from my Gallentean avatar I'm well aware of the tremendous success in it's use for CCP's flagship EVE Online game first hand. What about Eventlet or gevent? Well for now only Eventlet works with Twisted. However gevent claims to be faster since it's not a pure python implementation it instead uses libevent. It also has fewer idiosyncrasies and defects supposedly. The documentation there is minimal in comparison to Eventlet and it's maintained by 1 guy as far as I can tell. This makes me leery but all great projects start this way so... Then there's PyPy - I haven't even finished reading about that one yet - just saw it in this thread: Drawbacks of Stackless. So confusing - I'm wondering what the heck to do - sounds like Eventlet is probably the best bet but is it really stable enough? Anyone out there have any experience with it? Should we go with Stackless instead as it's been around and is proven technology - just like Twisted is as well - and they do work together nicely. But still I hate having to have a separate version of Python to do this. what to do.... This somewhat obnoxious blog entry hit the nail on the head for me though: Asynchronous IO for Grownups We're stuck using MySQL as well - I never knew how great PostgreSQL was until having had to work on a production OLTP system in MySQL instead - but that's another story. But if that monkey patch thing really works then wow. Just wow.

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  • Geb not working with chrome driver

    - by user2346867
    @Grapes([ @Grab("org.gebish:geb-core:0.9.0"), @Grab("org.gebish:geb-spock:0.9.0"), @Grab("org.seleniumhq.selenium:selenium-firefox-driver:2.33.0"), @Grab("org.seleniumhq.selenium:selenium-chrome-driver:2.33.0"), @Grab("org.seleniumhq.selenium:selenium-support:2.26.0"), @Grab( group='org.spockframework', module='spock-core', version='0.3' ), @Grab(group='org.gebish', module='geb-implicit-assertions', version='0.9.0') ]) import geb.Browser import geb.spock.GebReportingSpec import org.openqa.selenium.chrome.* import spock.lang.Specification import geb.navigator.NonEmptyNavigator import geb.navigator.factory.* System.setProperty("webdriver.chrome.driver", "C:\\chromedriver\\chromedriver.exe"); def browser = new Browser(driver: new ChromeDriver()) browser.go "http://www.google.com/" assert browser.title == "Google" browser.$("input", name: "q").value("query") When i try to run the above code i am getting the following error WARNING: Sanitizing stacktrace: java.lang.NoClassDefFoundError: Could not initialize class geb.navigator.NonEmptyNavigator at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:171) at geb.navigator.factory.DefaultInnerNavigatorFactory.class$(DefaultInnerNavigatorFactory.groovy) at geb.navigator.factory.DefaultInnerNavigatorFactory.$get$$class$geb$navigator$NonEmptyNavigator(DefaultInnerNavigatorFactory.groovy) at geb.navigator.factory.DefaultInnerNavigatorFactory.createNavigator(DefaultInnerNavigatorFactory.groovy:40) at geb.navigator.factory.InnerNavigatorFactory$createNavigator.call(Unknown Source) at geb.navigator.factory.AbstractNavigatorFactory.createFromWebElements(AbstractNavigatorFactory.groovy:44) at geb.navigator.factory.NavigatorFactory$createFromWebElements.callCurrent(Unknown Source) at geb.navigator.factory.BrowserBackedNavigatorFactory.getBase(BrowserBackedNavigatorFactory.groovy:33) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:1671) at groovy.lang.MetaClassImpl.getProperty(MetaClassImpl.java:3408) at geb.navigator.factory.AbstractNavigatorFactory.getProperty(AbstractNavigatorFactory.groovy) at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:47) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:227) at geb.content.NavigableSupport.getNavigator(NavigableSupport.groovy:39) at geb.content.NavigableSupport.$(NavigableSupport.groovy:96) at geb.content.NavigableSupport$$.call(Unknown Source) at geb.Page.$(Page.groovy) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1085) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909) at org.codehaus.groovy.runtime.InvokerHelper.invokePogoMethod(InvokerHelper.java:848) at org.codehaus.groovy.runtime.InvokerHelper.invokeMethod(InvokerHelper.java:831) at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodN(ScriptBytecodeAdapter.java:164) at geb.Browser.methodMissing(Browser.groovy:193) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaClassImpl.invokeMissingMethod(MetaClassImpl.java:837) Any idea on this how to resolve it ???

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  • Any significant performance improvement by using bitwise operators instead of plain int sums in C#?

    - by tunnuz
    Hello, I started working with C# a few weeks ago and I'm now in a situation where I need to build up a "bit set" flag to handle different cases in an algorithm. I have thus two options: enum RelativePositioning { LEFT = 0, RIGHT = 1, BOTTOM = 2, TOP = 3, FRONT = 4, BACK = 5 } pos = ((eye.X < minCorner.X ? 1 : 0) << RelativePositioning.LEFT) + ((eye.X > maxCorner.X ? 1 : 0) << RelativePositioning.RIGHT) + ((eye.Y < minCorner.Y ? 1 : 0) << RelativePositioning.BOTTOM) + ((eye.Y > maxCorner.Y ? 1 : 0) << RelativePositioning.TOP) + ((eye.Z < minCorner.Z ? 1 : 0) << RelativePositioning.FRONT) + ((eye.Z > maxCorner.Z ? 1 : 0) << RelativePositioning.BACK); Or: enum RelativePositioning { LEFT = 1, RIGHT = 2, BOTTOM = 4, TOP = 8, FRONT = 16, BACK = 32 } if (eye.X < minCorner.X) { pos += RelativePositioning.LEFT; } if (eye.X > maxCorner.X) { pos += RelativePositioning.RIGHT; } if (eye.Y < minCorner.Y) { pos += RelativePositioning.BOTTOM; } if (eye.Y > maxCorner.Y) { pos += RelativePositioning.TOP; } if (eye.Z > maxCorner.Z) { pos += RelativePositioning.FRONT; } if (eye.Z < minCorner.Z) { pos += RelativePositioning.BACK; } I could have used something as ((eye.X > maxCorner.X) << 1) but C# does not allow implicit casting from bool to int and the ternary operator was similar enough. My question now is: is there any performance improvement in using the first version over the second? Thank you Tommaso

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  • Why default constructor does not appear for value types?

    - by Arun
    The below snippet gives me a list of constructors and methods of a type. static void ReflectOnType(Type type) { Console.WriteLine(type.FullName); Console.WriteLine("------------"); List<ConstructorInfo> constructors = type.GetConstructors(BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic |BindingFlags.Instance | BindingFlags.Default).ToList(); List<MethodInfo> methods = type.GetMethods().ToList(); Type baseType = type.BaseType; while (baseType != null) { constructors.AddRange(baseType.GetConstructors(BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Default)); methods.AddRange(baseType.GetMethods()); baseType = baseType.BaseType; } Console.WriteLine("Reflection on {0} type", type.Name); for (int i = 0; i < constructors.Count; i++) { Console.Write("Constructor: {0}.{1}", constructors[i].DeclaringType.Name, constructors[i].Name); Console.Write("("); ParameterInfo[] parameterInfos = constructors[i].GetParameters(); if (parameterInfos.Length > 0) { for (int j = 0; j < parameterInfos.Length; j++) { if (j > 0) { Console.Write(", "); } Console.Write("{0} {1}", parameterInfos[j].ParameterType, parameterInfos[j].Name); } } Console.Write(")"); if (constructors[i].IsSpecialName) { Console.Write(" has 'SpecialName' attribute"); } Console.WriteLine(); } Console.WriteLine(); for (int i = 0; i < methods.Count; i++) { Console.Write("Method: {0}.{1}", methods[i].DeclaringType.Name, methods[i].Name); // Determine whether or not each field is a special name. if (methods[i].IsSpecialName) { Console.Write(" has 'SpecialName' attribute"); } Console.WriteLine(); } } But when I pass an ‘int’ type to this method, why don’t I see the implicit constructor in the output? Or, how do I modify the above code to list the default constructor as well (in case I’m missing something in my code).

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  • ASP.NET MVC 2 actionlink breaking after migration from MVC version 1

    - by thermal7
    Hi, I am migrating my application from asp.net mvc to mvc version 2 and am having the following issue. I have paging links << < that I include in each page. Like so: <% Html.RenderPartial("PagingControl", Model); %> They exist in an ascx file as follows. <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<BankingDB.Controllers.Utility.IPagedSortedObject>" %> <div class="paging"> <div class="previous-paging"> <!- error!! -><%= Model.HasPreviousPage ? Html.ActionLink("<<", "Index", Model.buildParams(1)) : "<<"%> <%= Model.HasPreviousPage ? Html.ActionLink("<", "Index", Model.buildParams(Model.PreviousPageIndex)) : "<"%> </div> <div class="paging-details"> Showing records <%= Model.BaseRecordIndex %> to <%= Model.MaxRecordIndex %> of <%= Model.TotalRecordCount %> </div> <div class="next-paging"> <%= Model.HasNextPage ? Html.ActionLink(">", "Index", Model.buildParams(Model.NextPageIndex)) : ">"%> <%= Model.HasNextPage ? Html.ActionLink(">>", "Index", Model.buildParams(Model.PageCount)) : ">>"%> </div> </div> When I try to access the page I get the error: CS0173: Type of conditional expression cannot be determined because there is no implicit conversion between 'System.Web.Mvc.MvcHtmlString' and 'string' The error is marked above and appears to be with the action link. Including the controller name doesn't help. Any ideas?

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  • Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

    - by ke3pup
    Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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  • Is the Scala 2.8 collections library a case of "the longest suicide note in history" ?

    - by oxbow_lakes
    First note the inflammatory subject title is a quotation made about the manifesto of a UK political party in the early 1980s. This question is subjective but it is a genuine question, I've made it CW and I'd like some opinions on the matter. Despite whatever my wife and coworkers keep telling me, I don't think I'm an idiot: I have a good degree in mathematics from the University of Oxford and I've been programming commercially for almost 12 years and in Scala for about a year (also commercially). I have just started to look at the Scala collections library re-implementation which is coming in the imminent 2.8 release. Those familiar with the library from 2.7 will notice that the library, from a usage perspective, has changed little. For example... > List("Paris", "London").map(_.length) res0: List[Int] List(5, 6) ...would work in either versions. The library is eminently useable: in fact it's fantastic. However, those previously unfamiliar with Scala and poking around to get a feel for the language now have to make sense of method signatures like: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That For such simple functionality, this is a daunting signature and one which I find myself struggling to understand. Not that I think Scala was ever likely to be the next Java (or /C/C++/C#) - I don't believe its creators were aiming it at that market - but I think it is/was certainly feasible for Scala to become the next Ruby or Python (i.e. to gain a significant commercial user-base) Is this going to put people off coming to Scala? Is this going to give Scala a bad name in the commercial world as an academic plaything that only dedicated PhD students can understand? Are CTOs and heads of software going to get scared off? Was the library re-design a sensible idea? If you're using Scala commercially, are you worried about this? Are you planning to adopt 2.8 immediately or wait to see what happens? Steve Yegge once attacked Scala (mistakenly in my opinion) for what he saw as its overcomplicated type-system. I worry that someone is going to have a field day spreading fud with this API (similarly to how Josh Bloch scared the JCP out of adding closures to Java). Note - I should be clear that, whilst I believe that Josh Bloch was influential in the rejection of the BGGA closures proposal, I don't ascribe this to anything other than his honestly-held beliefs that the proposal represented a mistake.

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  • Corner Cases, Unexpected and Unusual Matlab

    - by Mikhail
    Over the years, reading others code, I encountered and collected some examples of Matlab syntax which can be at first unusual and counterintuitive. Please, feel free to comment or complement this list. I verified it r2006a. set([], 'Background:Color','red') Matlab is very forgiving sometimes. In this case, setting properties to an array of objects works also with nonsense properties, at least when the array is empty. myArray([1,round(end/2)]) This use of end keyword may seem unclean but is sometimes very handy instead of using length(myArray). any([]) ~= all([]) Surprisigly any([]) returns false and all([]) returns true. And I always thought that all is stronger then any. EDIT: with not empty argument all() returns true for a subset of values for which any() returns true (e.g. truth table). This means that any() false implies all() false. This simple rule is being violated by Matlab with [] as argument. Loren also blogged about it. Select(Range(ExcelComObj)) Procedural style COM object method dispatch. Do not wonder that exist('Select') returns zero! [myString, myCell] Matlab makes in this case an implicit cast of string variable myString to cell type {myString}. It works, also if I would not expect it to do so. [double(1.8), uint8(123)] => 2 123 Another cast example. Everybody would probably expect uint8 value being cast to double but Mathworks have another opinion. a = 5; b = a(); It looks silly but you can call a variable with round brackets. Actually it makes sense because this way you can execute a function given its handle. a = {'aa', 'bb' 'cc', 'dd'}; Surprsisingly this code neither returns a vector nor rises an error but defins matrix, using just code layout. It is probably a relict from ancient times. set(hobj, {'BackgroundColor','ForegroundColor'},{'red','blue'}) This code does what you probably expect it to do. That function set accepts a struct as its second argument is a known fact and makes sense, and this sintax is just a cell2struct away. Equvalence rules are sometimes unexpected at first. For example 'A'==65 returns true (although for C-experts it is self-evident). About which further unexpected/unusual Matlab features are you aware?

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  • Parse int to string with stringstream

    - by SoulBeaver
    Well! I feel really stupid for this question, and I wholly don't mind if I get downvoted for this, but I guess I wouldn't be posting this if I had not at least made an earnest attempt at looking for the solution. I'm currently working on Euler Problem 4, finding the largest palindromic number of two three-digit numbers [100..999]. As you might guess, I'm at the part where I have to work with the integer I made. I looked up a few sites and saw a few standards for converting an Int to a String, one of which included stringstream. So my code looked like this: // tempTotal is my int value I want converted. void toString( int tempTotal, string &str ) { ostringstream ss; // C++ Standard compliant method. ss << tempTotal; str = ss.str(); // Overwrite referenced value of given string. } and the function calling it was: else { toString( tempTotal, store ); cout << loop1 << " x " << loop2 << "= " << store << endl; } So far, so good. I can't really see an error in what I've written, but the output gives me the address to something. It stays constant, so I don't really know what the program is doing there. Secondly, I tried .ToString(), string.valueOf( tempTotal ), (string)tempTotal, or simply store = temptotal. All refused to work. When I simply tried doing an implicit cast with store = tempTotal, it didn't give me a value at all. When I tried checking output it literally printed nothing. I don't know if anything was copied into my string that simply isn't a printable character, or if the compiler just ignored it. I really don't know. So even though I feel this is a really, really lame question, I just have to ask: How do I convert that stupid integer to a string with the stringstream? The other tries are more or less irrelevant for me, I just really want to know why my stringstream solution isn't working.

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  • Can anyone explain me the source code of python "import this"?

    - by byterussian
    If you open a Python interpreter, and type "import this", as you know, it prints: The Zen of Python, by Tim Peters Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than *right* now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those! In the python source(Lib/this.py) this text is generated by a curios piece of code: s = """Gur Mra bs Clguba, ol Gvz Crgref Ornhgvshy vf orggre guna htyl. Rkcyvpvg vf orggre guna vzcyvpvg. Fvzcyr vf orggre guna pbzcyrk. Pbzcyrk vf orggre guna pbzcyvpngrq. Syng vf orggre guna arfgrq. Fcnefr vf orggre guna qrafr. Ernqnovyvgl pbhagf. Fcrpvny pnfrf nera'g fcrpvny rabhtu gb oernx gur ehyrf. Nygubhtu cenpgvpnyvgl orngf chevgl. Reebef fubhyq arire cnff fvyragyl. Hayrff rkcyvpvgyl fvyraprq. Va gur snpr bs nzovthvgl, ershfr gur grzcgngvba gb thrff. Gurer fubhyq or bar-- naq cersrenoyl bayl bar --boivbhf jnl gb qb vg. Nygubhtu gung jnl znl abg or boivbhf ng svefg hayrff lbh'er Qhgpu. Abj vf orggre guna arire. Nygubhtu arire vf bsgra orggre guna *evtug* abj. Vs gur vzcyrzragngvba vf uneq gb rkcynva, vg'f n onq vqrn. Vs gur vzcyrzragngvba vf rnfl gb rkcynva, vg znl or n tbbq vqrn. Anzrfcnprf ner bar ubaxvat terng vqrn -- yrg'f qb zber bs gubfr!""" d = {} for c in (65, 97): for i in range(26): d[chr(i+c)] = chr((i+13) % 26 + c) print "".join([d.get(c, c) for c in s])

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  • Cannot figure out how to take in generic parameters for an Enterprise Framework library sql statemen

    - by KallDrexx
    I have written a specialized class to wrap up the enterprise library database functionality for easier usage. The reasoning for using the Enterprise Library is because my applications commonly connect to both oracle and sql server database systems. My wrapper handles both creating connection strings on the fly, connecting, and executing queries allowing my main code to only have to write a few lines of code to do database stuff and deal with error handling. As an example my ExecuteNonQuery method has the following declaration: /// <summary> /// Executes a query that returns no results (e.g. insert or update statements) /// </summary> /// <param name="sqlQuery"></param> /// <param name="parameters">Hashtable containing all the parameters for the query</param> /// <returns>The total number of records modified, -1 if an error occurred </returns> public int ExecuteNonQuery(string sqlQuery, Hashtable parameters) { // Make sure we are connected to the database if (!IsConnected) { ErrorHandler("Attempted to run a query without being connected to a database.", ErrorSeverity.Critical); return -1; } // Form the command DbCommand dbCommand = _database.GetSqlStringCommand(sqlQuery); // Add all the paramters foreach (string key in parameters.Keys) { if (parameters[key] == null) _database.AddInParameter(dbCommand, key, DbType.Object, null); else _database.AddInParameter(dbCommand, key, DbType.Object, parameters[key].ToString()); } return _database.ExecuteNonQuery(dbCommand); } _database is defined as private Database _database;. Hashtable parameters are created via code similar to p.Add("@param", value);. the issue I am having is that it seems that with enterprise library database framework you must declare the dbType of each parameter. This isn't an issue when you are calling the database code directly when forming the paramters but doesn't work for creating a generic abstraction class such as I have. In order to try and get around that I thought I could just use DbType.Object and figure the DB will figure it out based on the columns the sql is working with. Unfortunately, this is not the case as I get the following error: Implicit conversion from data type sql_variant to varchar is not allowed. Use the CONVERT function to run this query Is there any way to use generic parameters in a wrapper class or am I just going to have to move all my DB code into my main classes?

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  • Class template specializations with shared functionality

    - by Thomas
    I'm writing a simple maths library with a template vector type: template<typename T, size_t N> class Vector { public: Vector<T, N> &operator+=(Vector<T, N> const &other); // ... more operators, functions ... }; Now I want some additional functionality specifically for some of these. Let's say I want functions x() and y() on Vector<T, 2> to access particular coordinates. I could create a partial specialization for this: template<typename T> class Vector<T, 3> { public: Vector<T, 3> &operator+=(Vector<T, 3> const &other); // ... and again all the operators and functions ... T x() const; T y() const; }; But now I'm repeating everything that already existed in the generic template. I could also use inheritance. Renaming the generic template to VectorBase, I could do this: template<typename T, size_t N> class Vector : public VectorBase<T, N> { }; template<typename T> class Vector<T, 3> : public VectorBase<T, 3> { public: T x() const; T y() const; }; However, now the problem is that all operators are defined on VectorBase, so they return VectorBase instances. These cannot be assigned to Vector variables: Vector<float, 3> v; Vector<float, 3> w; w = 5 * v; // error: no conversion from VectorBase<float, 3> to Vector<float, 3> I could give Vector an implicit conversion constructor to make this possible: template<typename T, size_t N> class Vector : public VectorBase<T, N> { public: Vector(VectorBase<T, N> const &other); }; However, now I'm converting from Vector to VectorBase and back again. Even though the types are the same in memory, and the compiler might optimize all this away, it feels clunky and I don't really like to have potential run-time overhead for what is essentially a compile-time problem. Is there any other way to solve this?

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  • Go - Using a container/heap to implement a priority queue

    - by Seth Hoenig
    In the big picture, I'm trying to implement Dijkstra's algorithm using a priority queue. According to members of golang-nuts, the idiomatic way to do this in Go is to use the heap interface with a custom underlying data structure. So I have created Node.go and PQueue.go like so: //Node.go package pqueue type Node struct { row int col int myVal int sumVal int } func (n *Node) Init(r, c, mv, sv int) { n.row = r n.col = c n.myVal = mv n.sumVal = sv } func (n *Node) Equals(o *Node) bool { return n.row == o.row && n.col == o.col } And PQueue.go: // PQueue.go package pqueue import "container/vector" import "container/heap" type PQueue struct { data vector.Vector size int } func (pq *PQueue) Init() { heap.Init(pq) } func (pq *PQueue) IsEmpty() bool { return pq.size == 0 } func (pq *PQueue) Push(i interface{}) { heap.Push(pq, i) pq.size++ } func (pq *PQueue) Pop() interface{} { pq.size-- return heap.Pop(pq) } func (pq *PQueue) Len() int { return pq.size } func (pq *PQueue) Less(i, j int) bool { I := pq.data.At(i).(Node) J := pq.data.At(j).(Node) return (I.sumVal + I.myVal) < (J.sumVal + J.myVal) } func (pq *PQueue) Swap(i, j int) { temp := pq.data.At(i).(Node) pq.data.Set(i, pq.data.At(j).(Node)) pq.data.Set(j, temp) } And main.go: (the action is in SolveMatrix) // Euler 81 package main import "fmt" import "io/ioutil" import "strings" import "strconv" import "./pqueue" const MATSIZE = 5 const MATNAME = "matrix_small.txt" func main() { var matrix [MATSIZE][MATSIZE]int contents, err := ioutil.ReadFile(MATNAME) if err != nil { panic("FILE IO ERROR!") } inFileStr := string(contents) byrows := strings.Split(inFileStr, "\n", -1) for row := 0; row < MATSIZE; row++ { byrows[row] = (byrows[row])[0 : len(byrows[row])-1] bycols := strings.Split(byrows[row], ",", -1) for col := 0; col < MATSIZE; col++ { matrix[row][col], _ = strconv.Atoi(bycols[col]) } } PrintMatrix(matrix) sum, len := SolveMatrix(matrix) fmt.Printf("len: %d, sum: %d\n", len, sum) } func PrintMatrix(mat [MATSIZE][MATSIZE]int) { for r := 0; r < MATSIZE; r++ { for c := 0; c < MATSIZE; c++ { fmt.Printf("%d ", mat[r][c]) } fmt.Print("\n") } } func SolveMatrix(mat [MATSIZE][MATSIZE]int) (int, int) { var PQ pqueue.PQueue var firstNode pqueue.Node var endNode pqueue.Node msm1 := MATSIZE - 1 firstNode.Init(0, 0, mat[0][0], 0) endNode.Init(msm1, msm1, mat[msm1][msm1], 0) if PQ.IsEmpty() { // make compiler stfu about unused variable fmt.Print("empty") } PQ.Push(firstNode) // problem return 0, 0 } The problem is, upon compiling i get the error message: [~/Code/Euler/81] $ make 6g -o pqueue.6 Node.go PQueue.go 6g main.go main.go:58: implicit assignment of unexported field 'row' of pqueue.Node in function argument make: *** [all] Error 1 And commenting out the line PQ.Push(firstNode) does satisfy the compiler. But I don't understand why I'm getting the error message in the first place. Push doesn't modify the argument in any way.

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  • Android HelloGoogleMaps to OSMdroid (Open Street Maps)

    - by birgit
    I am trying to reproduce a working HelloGoogleMaps app in Open Street Maps - but I have trouble including the itemized overlay in OSMdroid. I have looked at several resources but I cannot figure out how to fix the error on OsmItemizedOverlay - I guess I am constructing OsmItemizedOverlay wrongly or have a mixup with OsmItemizedOverlay and ItemizedOverlay? But everything I tried to change just raised more errors... "Implicit super constructor ItemizedOverlay() is undefined. Must explicitly invoke another constructor" "Cannot make a static reference to the non-static method setMarker(Drawable) from the type OverlayItem" - I hope someone can help me getting the class definition straight? Thanks so much! package com.example.osmdroiddemomap; import java.util.ArrayList; import android.app.AlertDialog; import android.content.Context; import android.graphics.Point; import android.graphics.drawable.Drawable; import org.osmdroid.api.IMapView; import org.osmdroid.views.*; import org.osmdroid.views.overlay.*; import org.osmdroid.views.overlay.OverlayItem.HotspotPlace; public class OsmItemizedOverlay extends ItemizedOverlay<OverlayItem> { Context mContext; private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); //ERRORS are raised by the following 3 lines: public OsmItemizedOverlay(Drawable defaultMarker, Context context) { OverlayItem.setMarker(defaultMarker); OverlayItem.setMarkerHotspot(HotspotPlace.CENTER); mContext = context; } public void addOverlay(OverlayItem overlay) { mOverlays.add(overlay); populate(); } @Override protected OverlayItem createItem(int i) { return mOverlays.get(i); } @Override public int size() { return mOverlays.size(); } protected boolean onTap(int index) { OverlayItem item = mOverlays.get(index); AlertDialog.Builder dialog = new AlertDialog.Builder(mContext); dialog.setTitle(item.getTitle()); dialog.setMessage(item.getSnippet()); dialog.show(); return true; } @Override public boolean onSnapToItem(int arg0, int arg1, Point arg2, IMapView arg3) { // TODO Auto-generated method stub return false; } }

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  • .NET: Is there a way to finagle a default namespace in an XPath 1.0 query?

    - by Cheeso
    I'm building a tool that performs xpath 1.0 queries on XHTML documents. The requirement to use a namespace prefix in the query is killing me. The query looks like this: html/body/div[@class='contents']/div[@class='body']/ div[@class='pgdbbyauthor']/h2[a[@name][starts-with(.,'Quick')]]/ following-sibling::ul[1]/li/a (all on one line) ...which is bad enough, except because it's xpath 1.0, I need to use an explicit namespace prefix on each QName, so it looks like this: ns1:html/ns1:body/ns1:div[@class='contents']/ns1:div[@class='body']/ ns1:div[@class='pgdbbyauthor']/ns1:h2[ns1:a[@name][starts-with(.,'Quick')]]/ following-sibling::ns1:ul[1]/ns1:li/ns1:a To set up the query, I do something like this: var xpathDoc = new XPathDocument(new StringReader(theText)); var nav = xpathDoc.CreateNavigator(); var xmlns = new XmlNamespaceManager(nav.NameTable); foreach (string prefix in xmlNamespaces.Keys) xmlns.AddNamespace(prefix, xmlNamespaces[prefix]); XPathNodeIterator selection = nav.Select(xpathExpression, xmlns); But what I want is for the xpathExpression to use the implicit default namespace. Is there a way for me to transform the unadorned xpath expression, after it's been written, to inject a namespace prefix for each element name in the query? I'm thinking, anything between two slashes, I could inject a prefix there. Excepting of course axis names like "parent::" and "preceding-sibling::" . And wildcards. That's what I mean by "finagle a default namespace". Is this hack gonna work? Addendum Here's what I mean. suppose I have an xpath expression, and before passing it to nav.Select(), I transform it. Something like this: string FixupWithDefaultNamespace(string expr) { string s = expr; s = Regex.Replace(s, "^(?!::)([^/:]+)(?=/)", "ns1:$1"); // beginning s = Regex.Replace(s, "/([^/:]+)(?=/)", "/ns1:$1"); // stanza s = Regex.Replace(s, "::([A-Za-z][^/:*]*)(?=/)", "::ns1:$1"); // axis specifier s = Regex.Replace(s, "\\[([A-Za-z][^/:*\\(]*)(?=[\\[\\]])", "[ns1:$1"); // predicate s = Regex.Replace(s, "/([A-Za-z][^/:]*)(?!<::)$", "/ns1:$1"); // end s = Regex.Replace(s, "^([A-Za-z][^/:]*)$", "ns1:$1"); // edge case s = Regex.Replace(s, "([-A-Za-z]+)\\(([^/:\\.,\\)]+)(?=[,\\)])", "$1(ns1:$2"); // xpath functions return s; } This actually works for simple cases I tried. To use the example from above - if the input is the first xpath expression, the output I get is the 2nd one, with all the ns1 prefixes. The real question is, is it hopeless to expect this Regex.Replace approach to work, as the xpath expressions get more complicated?

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  • C# Property Access vs Interface Implementation

    - by ehdv
    I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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  • C++ addition overload ambiguity

    - by Nate
    I am coming up against a vexing conundrum in my code base. I can't quite tell why my code generates this error, but (for example) std::string does not. class String { public: String(const char*str); friend String operator+ ( const String& lval, const char *rval ); friend String operator+ ( const char *lval, const String& rval ); String operator+ ( const String& rval ); }; The implementation of these is easy enough to imagine on your own. My driver program contains the following: String result, lval("left side "), rval("of string"); char lv[] = "right side ", rv[] = "of string"; result = lv + rval; printf(result); result = (lval + rv); printf(result); Which generates the following error in gcc 4.1.2: driver.cpp:25: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: String.h:22: note: candidate 1: String operator+(const String&, const char*) String.h:24: note: candidate 2: String String::operator+(const String&) So far so good, right? Sadly, my String(const char *str) constructor is so handy to have as an implicit constructor, that using the explicit keyword to solve this would just cause a different pile of problems. Moreover... std::string doesn't have to resort to this, and I can't figure out why. For example, in basic_string.h, they are declared as follows: template<typename _CharT, typename _Traits, typename _Alloc> basic_string<_CharT, _Traits, _Alloc> operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, const basic_string<_CharT, _Traits, _Alloc>& __rhs) template<typename _CharT, typename _Traits, typename _Alloc> basic_string<_CharT,_Traits,_Alloc> operator+(const _CharT* __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs); and so on. The basic_string constructor is not declared explicit. How does this not cause the same error I'm getting, and how can I achieve the same behavior??

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  • C#/.NET Project - Am I setting things up correctly?

    - by JustLooking
    1st solution located: \Common\Controls\Controls.sln and its project: \Common\Controls\Common.Controls\Common.Controls.csproj Description: This is a library that contains this class: public abstract class OurUserControl : UserControl { // Variables and other getters/setters common to our UserControls } 2nd solution located: \AControl\AControl.sln and its project: \AControl\AControl\AControl.csproj Description: Of the many forms/classes, it will contain this class: using Common.Controls; namespace AControl { public partial class AControl : OurUserControl { // The implementation } } A note about adding references (not sure if this is relevant): When I add references (for projects I create), using the names above: 1. I add Common.Controls.csproj to AControl.sln 2. In AControl.sln I turn off the build of Common.Controls.csproj 3. I add the reference to Common.Controls (by project) to AControl.csproj. This is the (easiest) way I know how to get Debug versions to match Debug References, and Release versions to match Release References. Now, here is where the issue lies (the 3rd solution/project that actually utilizes the UserControl): 3rd solution located: \MainProj\MainProj.sln and its project: \MainProj\MainProj\MainProj.csproj Description: Here's a sample function in one of the classes: private void TestMethod<T>() where T : Common.Controls.OurUserControl, new() { T TheObject = new T(); TheObject.OneOfTheSetters = something; TheObject.AnotherOfTheSetters = something_else; // Do stuff with the object } We might call this function like so: private void AnotherMethod() { TestMethod<AControl.AControl>(); } This builds, runs, and works. No problem. The odd thing is after I close the project/solution and re-open it, I have red squigglies everywhere. I bring up my error list and I see tons of errors (anything that deals with AControl will be noted as an error). I'll see errors such as: The type 'AControl.AControl' cannot be used as type parameter 'T' in the generic type or method 'MainProj.MainClass.TestMethod()'. There is no implicit reference conversion from 'AControl.AControl' to 'Common.Controls.OurUserControl'. or inside the actual method (the properties located in the abstract class): 'AControl.AControl' does not contain a definition for 'OneOfTheSetters' and no extension method 'OneOfTheSetters' accepting a first argument of type 'AControl.AControl' could be found (are you missing a using directive or an assembly reference?) Meanwhile, I can still build and run the project (then the red squigglies go away until I re-open the project, or close/re-open the file). It seems to me that I might be setting up the projects incorrectly. Thoughts?

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  • What to Expect in Rails 4

    - by mikhailov
    Rails 4 is nearly there, we should be ready before it released. Most developers are trying hard to keep their application on the edge. Must see resources: 1) @sikachu talk: What to Expect in Rails 4.0 - YouTube 2) Rails Guides release notes: http://edgeguides.rubyonrails.org/4_0_release_notes.html There is a mix of all major changes down here: ActionMailer changes excerpt: Asynchronously send messages via the Rails Raise an ActionView::MissingTemplate exception when no implicit template could be found ActionPack changes excerpt Added controller-level etag additions that will be part of the action etag computation Add automatic template digests to all CacheHelper#cache calls (originally spiked in the cache_digests plugin) Add Routing Concerns to declare common routes that can be reused inside others resources and routes Added ActionController::Live. Mix it in to your controller and you can stream data to the client live truncate now always returns an escaped HTML-safe string. The option :escape can be used as false to not escape the result Added ActionDispatch::SSL middleware that when included force all the requests to be under HTTPS protocol ActiveModel changes excerpt AM::Validation#validates ability to pass custom exception to :strict option Changed `AM::Serializers::JSON.include_root_in_json' default value to false. Now, AM Serializers and AR objects have the same default behaviour Added ActiveModel::Model, a mixin to make Ruby objects work with AP out of box Trim down Active Model API by removing valid? and errors.full_messages ActiveRecord changes excerpt Use native mysqldump command instead of structure_dump method when dumping the database structure to a sql file. Attribute predicate methods, such as article.title?, will now raise ActiveModel::MissingAttributeError if the attribute being queried for truthiness was not read from the database, instead of just returning false ActiveRecord::SessionStore has been extracted from Active Record as activerecord-session_store gem. Please read the README.md file on the gem for the usage Fix reset_counters when there are multiple belongs_to association with the same foreign key and one of them have a counter cache Raise ArgumentError if list of attributes to change is empty in update_all Add Relation#load. This method explicitly loads the records and then returns self Deprecated most of the 'dynamic finder' methods. All dynamic methods except for find_by_... and find_by_...! are deprecated Added ability to ActiveRecord::Relation#from to accept other ActiveRecord::Relation objects Remove IdentityMap ActiveSupport changes excerpt ERB::Util.html_escape now escapes single quotes ActiveSupport::Callbacks: deprecate monkey patch of object callbacks Replace deprecated memcache-client gem with dalli in ActiveSupport::Cache::MemCacheStore Object#try will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the new Object#try! Object#try can't call private methods Add ActiveSupport::Deprecations.behavior = :silence to completely ignore Rails runtime deprecations What are the most important changes for you?

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  • Why are static classes considered “classes” and “reference types”?

    - by Timwi
    I’ve been pondering about the C# and CIL type system today and I’ve started to wonder why static classes are considered classes. There are many ways in which they are not really classes: A “normal” class can contain non-static members, a static class can’t. In this respect, a class is more similar to a struct than it is to a static class, and yet structs have a separate name. You can have a reference to an instance of a “normal” class, but not a static class (despite it being considered a “reference type”). In this respect, a class is more similar to an interface than it is to a static class, and yet interfaces have a separate name. The name of a static class can never be used in any place where a type name would normally fit: you can’t declare a variable of this type, you can’t use it as a base type, and you can’t use it as a generic type parameter. In this respect, static classes are somewhat more like namespaces. A “normal” class can implement interfaces. Once again, that makes classes more similar to structs than to static classes. A “normal” class can inherit from another class. It is also bizarre that static classes are considered to derive from System.Object. Although this allows them to “inherit” the static methods Equals and ReferenceEquals, the purpose of that inheritance is questionable as you would call those methods on object anyway. C# even allows you to specify that useless inheritance explicitly on static classes, but not on interfaces or structs, where the implicit derivation from object and System.ValueType, respectively, actually has a purpose. Regarding the subset-of-features argument: Static classes have a subset of the features of classes, but they also have a subset of the features of structs. All of the things that make a class distinct from the other kinds of type, do not seem to apply to static classes. Regarding the typeof argument: Making a static class into a new and different kind of type does not preclude it from being used in typeof. Given the sheer oddity of static classes, and the scarcity of similarities between them and “normal” classes, shouldn’t they have been made into a separate kind of type instead of a special kind of class?

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  • Marshalling non-Blittable Structs from C# to C++

    - by Greggo
    I'm in the process of rewriting an overengineered and unmaintainable chunk of my company's library code that interfaces between C# and C++. I've started looking into P/Invoke, but it seems like there's not much in the way of accessible help. We're passing a struct that contains various parameters and settings down to unmanaged codes, so we're defining identical structs. We don't need to change any of those parameters on the C++ side, but we do need to access them after the P/Invoked function has returned. My questions are: What is the best way to pass strings? Some are short (device id's which can be set by us), and some are file paths (which may contain Asian characters) Should I pass an IntPtr to the C# struct or should I just let the Marshaller take care of it by putting the struct type in the function signature? Should I be worried about any non-pointer datatypes like bools or enums (in other, related structs)? We have the treat warnings as errors flag set in C++ so we can't use the Microsoft extension for enums to force a datatype. Is P/Invoke actually the way to go? There was some Microsoft documentation about Implicit P/Invoke that said it was more type-safe and performant. For reference, here is one of the pairs of structs I've written so far: C++ /** Struct used for marshalling Scan parameters from managed to unmanaged code. */ struct ScanParameters { LPSTR deviceID; LPSTR spdClock; LPSTR spdStartTrigger; double spinRpm; double startRadius; double endRadius; double trackSpacing; UINT64 numTracks; UINT32 nominalSampleCount; double gainLimit; double sampleRate; double scanHeight; LPWSTR qmoPath; //includes filename LPWSTR qzpPath; //includes filename }; C# /// <summary> /// Struct used for marshalling scan parameters between managed and unmanaged code. /// </summary> [StructLayout(LayoutKind.Sequential)] public struct ScanParameters { [MarshalAs(UnmanagedType.LPStr)] public string deviceID; [MarshalAs(UnmanagedType.LPStr)] public string spdClock; [MarshalAs(UnmanagedType.LPStr)] public string spdStartTrigger; public Double spinRpm; public Double startRadius; public Double endRadius; public Double trackSpacing; public UInt64 numTracks; public UInt32 nominalSampleCount; public Double gainLimit; public Double sampleRate; public Double scanHeight; [MarshalAs(UnmanagedType.LPWStr)] public string qmoPath; [MarshalAs(UnmanagedType.LPWStr)] public string qzpPath; }

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