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• Fast comparison of char arrays?

  - by StackedCrooked

  I'm currently working in a codebase where IPv4 addresses are represented as pointers to u_int8. The equality operator is implemented like this: bool Ipv4Address::operator==(const u_int8 * inAddress) const { return (*(u_int32*) this->myBytes == *(u_int32*) inAddress); } This is probably the fasted solution, but it causes the GCC compiler warning: ipv4address.cpp:65: warning: dereferencing type-punned pointer will break strict-aliasing rules How can I rewrite the comparison correctly without breaking strict-aliasing rules and without losing performance points? I have considered using either memcmp or this macro: #define IS_EQUAL(a, b) \ (a[0] == b[0] && a[1] == b[1] && a[2] == b[2] && a[3] == b[3]) I'm thinking that the macro is the fastest solution. What do you recommend?

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• PHP file modification time in milliseconds

  - by Steven Rosato

  I there, I am currently writing a unit test which asserts that a file did not get modified. The test code execution takes less than one second and therefore I would like to know if it is possible to retrieve the file modification time in milliseconds. filemtime() function returns the UNIX timestamp in seconds. My current solution is using the sleep(1) function which will assure me that 1 second passed before checking if it was modified or not. I don't like that solution since it slows down the test by a great deal. I cannot assert the content equality via get_file_contents() since the data that can be rewritten would be the same. I am guessing it is impossible, is it?

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• Unicode string handling using Windows API

  - by DeadMG

  I always assumed that Unicode string handling was some dark art. However, I've seen that the Windows API has functions for comparing Unicode strings, for example. Does that mean that it's actually feasible to write a Unicode string class that can perform simple actions like sorting, equality comparison, and extraction from a file? Or are there hidden gotchas in the use of these functions that makes it actually a really bad idea? I'm just looking at libraries like ICU and they seem incredibly over-complicated compared to what a Unicode string class backed by the Windows API could actually look like, which would resemble the Standard string classes quite closely.

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• How to filter/sort/rank object model nodes?

  - by BCS

  I have some kind of object model and I need to filter and sort it's nodes for some kind of property. What kinds of automated systems exist to generate and select properties of the object model that correlate to what I want? (I'm intentionally being abstract and non-specific) I'm thinking of a system that works kind of like spam filters or supervised classification systems in that given an example data set it identifies rules that find nodes of interest. However I'm looking for a more general system in that it shouldn't require any design time information about the object model. It should work equality well as a spam filter on e-mail, a bug finder on a code base, an interest filter in a newsgroup or bot accounts finder on a social networking site. As long as it can explore the object model via reflection and be given a set of "interesting" nodes, it should be able to find rules that will find more nodes like them.

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• When is (true == x) === !!x false?

  - by Paul S.

  JavaScript has different equality comparison operators Equal == Strict equal === It also has a logical NOT ! and I've tended to think of using a double logical NOT, !!x, as basically the same as true == x. However I know this is not always the case, e.g. x = [] because [] is truthy for ! but falsy for ==. So, for which xs would (true == x) === !!x give false? Alternatively, what is falsy by == but not !! (or vice versa)?

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• Why does SQL Server consider N'????' and N'???' to be equal?

  - by Aidan Ryan

  We are testing our application for Unicode compatibility and have been selecting random characters outside the Latin character set for testing. On both Latin and Japanese-collated systems the following equality is true (U+3422): N'????' = N'???' but the following is not (U+30C1): N'????' = N'???' This was discovered when a test case using the first example (using U+3422) violated a unique index. Do we need to be more selective about the characters we use for testing? Obviously we don't know the semantic meaning of the above comparisons. Would this behavior be obvious to a native speaker?

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• Please Stop Voting Against a Candidate

  - by Brian Lanham

  DISCLAIMER:  This is not a post about “Romney” or “Obama”.  This is not a post for whom I am voting.  This is simply a post to address an issue that I cannot ignore any longer.  This two-party system that we have allowed to establish a foothold is killing this country.    More than 2 Options I was recently asked, “If you had to choose Romney or Obama who would you pick?”  I replied “Non sequiter.  The founders of this nation ensured that I never have to pick from only two candidates.”  But somehow that is the way this country’s citizens think.  I told someone last week that there are around 20 candidates for president and she was genuinely surprised.  (There are actually 25 candidates.)  She had no idea there were that many and, even though she knew there are more, she didn’t know any names beyond Romney and Obama.  Well, I am going to try and educate people like her on other options. Vote for a Candidate, not against another Candidate So this post is the first in a series with a little bit of information about each candidate for president.  I implore you…I beg you, please do your civic duty and conduct a little bit of investigation and research on your own to find the right candidate for you.  Hey, if your candidate is Romney or Obama, that’s fine.  As long as it’s an educated decision.  But please…stop voting against a candidate.  Start voting for a candidate. A List of CandidatesAs I mentioned, I am going to write a little something about each candidate and I’m going to go by alphabetical order by PARTY, then by CANDIDATE LAST NAME so as to not show any bias. P.S. – If you want to know the candidate I selected I am happy to tell you.  But that’s not what this series is about.PARTYCANDIDATEAmerica's Party   Tom HoeflingAmerican Third Position PartyMerlin MillerAmericans Elect PartyNo candidates met the requirement to enter into the online caucus.Constitution PartyVirgil GoodeDemocratic Party   Barack ObamaGrassroots Party   Jim CarlsonGreen Party   Jill SteinIndependent American Party   Will ChristensenJustice PartyRocky AndersonLibertarian Party   Gary JohnsonObjectivist PartyTom StevensPeace and Freedom Party   Roseanne BarrReform PartyAndre BarnettRepublican PartyMitt RomneySocialism and Liberation PartyPeta LindsaySocialist Equality PartyJerry WhiteSocialist Party USAStewart AlexanderSocialist Workers PartyJames HarrisIndependent Candidates Jeff BossRichard DuncanJerry Litzel Dean Morstad Jill Reed Randall TerrySheila Tittle Michael Vargo

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• How to perform Cross Join with Linq

  - by berthin

  Cross join consists to perform a Cartesian product of two sets or sequences. The following example shows a simple Cartesian product of the sets A and B: A (a1, a2) B (b1, b2) => C (a1 b1,            a1 b2,            a2 b1,            a2, b2 ) is the Cartesian product's result. Linq to Sql allows using Cross join operations. Cross join is not equijoin, means that no predicate expression of equality in the Join clause of the query. To define a cross join query, you can use multiple from clauses. Note that there's no explicit operator for the cross join. In the following example, the query must join a sequence of Product with a sequence of Pricing Rules: 1: //Fill the data source 2: var products = new List<Product> 3: { 4: new Product{ProductID="P01",ProductName="Amaryl"}, 5: new Product {ProductID="P02", ProductName="acetaminophen"} 6: }; 7:  8: var pricingRules = new List<PricingRule> 9: { 10: new PricingRule {RuleID="R_1", RuleType="Free goods"}, 11: new PricingRule {RuleID="R_2", RuleType="Discount"}, 12: new PricingRule {RuleID="R_3", RuleType="Discount"} 13: }; 14: 15: //cross join query 16: var crossJoin = from p in products 17: from r in pricingRules 18: select new { ProductID = p.ProductID, RuleID = r.RuleID };   Below the definition of the two entities using in the above example.   1: public class Product 2: { 3: public string ProductID { get; set; } 4: public string ProductName { get; set; } 5: } 1: public class PricingRule 2: { 3: public string RuleID { get; set; } 4: public string RuleType { get; set; } 5: }   Doing this: 1: foreach (var result in crossJoin) 2: { 3: Console.WriteLine("({0} , {1})", result.ProductID, result.RuleID); 4: }   The output should be similar on this:   ( P01   -    R_1 )   ( P01   -    R_2 )   ( P01   -    R_3 )   ( P02   -    R_1 )   ( P02   -    R_2 )   ( P02   -    R_3) Conclusion Cross join operation is useful when performing a Cartesian product of two sequences object. However, it can produce very large result sets that may caused a problem of performance. So use with precautions :)

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• Linked List manipulation, issues retrieving data c++

  - by floatfil

  I'm trying to implement some functions to manipulate a linked list. The implementation is a template typename T and the class is 'List' which includes a 'head' pointer and also a struct: struct Node { // the node in a linked list T* data; // pointer to actual data, operations in T Node* next; // pointer to a Node }; Since it is a template, and 'T' can be any data, how do I go about checking the data of a list to see if it matches the data input into the function? The function is called 'retrieve' and takes two parameters, the data and a pointer: bool retrieve(T target, T*& ptr); // This is the prototype we need to use for the project "bool retrieve : similar to remove, but not removed from list. If there are duplicates in the list, the first one encountered is retrieved. Second parameter is unreliable if return value is false. E.g., " Employee target("duck", "donald"); success = company1.retrieve(target, oneEmployee); if (success) { cout << "Found in list: " << *oneEmployee << endl; } And the function is called like this: company4.retrieve(emp3, oneEmployee) So that when you cout *oneEmployee, you'll get the data of that pointer (in this case the data is of type Employee). (Also, this is assuming all data types have the apropriate overloaded operators) I hope this makes sense so far, but my issue is in comparing the data in the parameter and the data while going through the list. (The data types that we use all include overloads for equality operators, so oneData == twoData is valid) This is what I have so far: template <typename T> bool List<T>::retrieve(T target , T*& ptr) { List<T>::Node* dummyPtr = head; // point dummy pointer to what the list's head points to for(;;) { if (*dummyPtr->data == target) { // EDIT: it now compiles, but it breaks here and I get an Access Violation error. ptr = dummyPtr->data; // set the parameter pointer to the dummy pointer return true; // return true } else { dummyPtr = dummyPtr->next; // else, move to the next data node } } return false; } Here is the implementation for the Employee class: //-------------------------- constructor ----------------------------------- Employee::Employee(string last, string first, int id, int sal) { idNumber = (id >= 0 && id <= MAXID? id : -1); salary = (sal >= 0 ? sal : -1); lastName = last; firstName = first; } //-------------------------- destructor ------------------------------------ // Needed so that memory for strings is properly deallocated Employee::~Employee() { } //---------------------- copy constructor ----------------------------------- Employee::Employee(const Employee& E) { lastName = E.lastName; firstName = E.firstName; idNumber = E.idNumber; salary = E.salary; } //-------------------------- operator= --------------------------------------- Employee& Employee::operator=(const Employee& E) { if (&E != this) { idNumber = E.idNumber; salary = E.salary; lastName = E.lastName; firstName = E.firstName; } return *this; } //----------------------------- setData ------------------------------------ // set data from file bool Employee::setData(ifstream& inFile) { inFile >> lastName >> firstName >> idNumber >> salary; return idNumber >= 0 && idNumber <= MAXID && salary >= 0; } //------------------------------- < ---------------------------------------- // < defined by value of name bool Employee::operator<(const Employee& E) const { return lastName < E.lastName || (lastName == E.lastName && firstName < E.firstName); } //------------------------------- <= ---------------------------------------- // < defined by value of inamedNumber bool Employee::operator<=(const Employee& E) const { return *this < E || *this == E; } //------------------------------- > ---------------------------------------- // > defined by value of name bool Employee::operator>(const Employee& E) const { return lastName > E.lastName || (lastName == E.lastName && firstName > E.firstName); } //------------------------------- >= ---------------------------------------- // < defined by value of name bool Employee::operator>=(const Employee& E) const { return *this > E || *this == E; } //----------------- operator == (equality) ---------------- // if name of calling and passed object are equal, // return true, otherwise false // bool Employee::operator==(const Employee& E) const { return lastName == E.lastName && firstName == E.firstName; } //----------------- operator != (inequality) ---------------- // return opposite value of operator== bool Employee::operator!=(const Employee& E) const { return !(*this == E); } //------------------------------- << --------------------------------------- // display Employee object ostream& operator<<(ostream& output, const Employee& E) { output << setw(4) << E.idNumber << setw(7) << E.salary << " " << E.lastName << " " << E.firstName << endl; return output; } I will include a check for NULL pointer but I just want to get this working and will test it on a list that includes the data I am checking. Thanks to whoever can help and as usual, this is for a course so I don't expect or want the answer, but any tips as to what might be going wrong will help immensely!

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• concurrency::accelerator_view

  - by Daniel Moth

  Overview We saw previously that accelerator represents a target for our C++ AMP computation or memory allocation and that there is a notion of a default accelerator. We ended that post by introducing how one can obtain accelerator_view objects from an accelerator object through the accelerator class's default_view property and the create_view method. The accelerator_view objects can be thought of as handles to an accelerator. You can also construct an accelerator_view given another accelerator_view (through the copy constructor or the assignment operator overload). Speaking of operator overloading, you can also compare (for equality and inequality) two accelerator_view objects between them to determine if they refer to the same underlying accelerator. We'll see later that when we use concurrency::array objects, the allocation of data takes place on an accelerator at array construction time, so there is a constructor overload that accepts an accelerator_view object. We'll also see later that a new concurrency::parallel_for_each function overload can take an accelerator_view object, so it knows on what target to execute the computation (represented by a lambda that the parallel_for_each also accepts). Beyond normal usage, accelerator_view is a quality of service concept that offers isolation to multiple "consumers" of an accelerator. If in your code you are accessing the accelerator from multiple threads (or, in general, from different parts of your app), then you'll want to create separate accelerator_view objects for each thread. flush, wait, and queuing_mode When you create an accelerator_view via the create_view method of the accelerator, you pass in an option of immediate or deferred, which are the two members of the queuing_mode enum. At any point you can access this value from the queuing_mode property of the accelerator_view. When the queuing_mode value is immediate (which is the default), any commands sent to the device such as kernel invocations and data transfers (e.g. parallel_for_each and copy, as we'll see in future posts), will get submitted as soon as the runtime sees fit (that is the definition of immediate). When the value of queuing_mode is deferred, the commands will be batched up. To send all buffered commands to the device for execution, there is a non-blocking flush method that you can call. If you wish to block until all the commands have been sent, there is a wait method you can call. Deferring is a more advanced scenario aimed at performance gains when you are submitting many device commands and you want to avoid the tiny overhead of flushing/submitting each command separately. Querying information Just like accelerator, accelerator_view exposes the is_debug and version properties. In fact, you can always access the accelerator object from the accelerator property on the accelerator_view class to access the accelerator interface we looked at previously. Interop with D3D (aka DX) In a later post I'll show an example of an app that uses C++ AMP to compute data that is used in pixel shaders. In those scenarios, you can benefit by integrating C++ AMP into your graphics pipeline and one of the building blocks for that is being able to use the same device context from both the compute kernel and the other shaders. You can do that by going from accelerator_view to device context (and vice versa), through part of our interop API in amp.h: *get_device, create_accelerator_view. More on those in a later post. Comments about this post by Daniel Moth welcome at the original blog.

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• Get to Know a Candidate (8 of 25): Rocky Anderson&ndash;Justice Party

  - by Brian Lanham

  DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Ross Carl “Rocky” Anderson served two terms as the 33rd mayor of Salt Lake City, Utah, between 2000 and 2008.  He is the Executive Director of High Road for Human Rights.  Prior to serving as Mayor, he practiced law for 21 years in Salt Lake City, during which time he was listed in Best Lawyers in America, was rated A-V (highest rating) by Martindale-Hubbell, served as Chair of the Utah State Bar Litigation Section[4] and was Editor-in-Chief of, and a contributor to, Voir Dire legal journal. As mayor, Anderson rose to nationwide prominence as a champion of several national and international causes, including climate protection, immigration reform, restorative criminal justice, LGBT rights, and an end to the "war on drugs". Before and after the invasion by the U.S. of Iraq in 2003, Anderson was a leading opponent of the invasion and occupation of Iraq and related human rights abuses. Anderson was the only mayor of a major U.S. city who advocated for the impeachment of President George W. Bush, which he did in many venues throughout the United States. Anderson's work and advocacy led to local, national, and international recognition in numerous spheres, including being named by Business Week as one of the top twenty activists in the world on climate change,serving on the Newsweek Global Environmental Leadership Advisory Board, and being recognized by the Human Rights Campaign as one of the top ten straight advocates in the United States for LGBT equality. He has also received numerous awards for his work, including the EPA Climate Protection Award, the Sierra Club Distinguished Service Award, the Respect the Earth Planet Defender Award, the National Association of Hispanic Publications Presidential Award, The Drug Policy Alliance Richard J. Dennis Drugpeace Award, the Progressive Democrats of America Spine Award, the League of United Latin American Citizens Profile in Courage Award, the Bill of Rights Defense Committee Patriot Award, the Code Pink (Salt Lake City) Pink Star honor, the Morehouse University Gandhi, King, Ikeda Award, and the World Leadership Award for environmental programs. Formerly a member of the Democratic Party, Anderson expressed his disappointment with that Party in 2011, stating, “The Constitution has been eviscerated while Democrats have stood by with nary a whimper. It is a gutless, unprincipled party, bought and paid for by the same interests that buy and pay for the Republican Party." Anderson announced his intention to run for President in 2012 as a candidate for the newly-formed Justice Party. Although founded by Rocky Anderson of Utah, the Justice Party was first recognized by Mississippi and describes itself as advocating economic justice through measures such as green jobs and a right to organize, environment justice through enforcing employee safeguards in trade agreements, and social and civic justice through universal health care. In its first press release, the Utah Justice Party set forth its goals for justice in the economic, environmental, social and civic realms, along with a call to rid the corrupting influence of big money from government, to reverse the erosion of rights guaranteed by the Constitution, and to stop draining American resources to support illegal wars of aggression. Its press release says its grassroots supporters believe that now is the time for all to "shed their skeptical view that their voices don't matter", that "our 2-party system is a 'duopoly' controlled by the same corporate and military interests", and that the people must act to ensure "that our nation will achieve a brighter, sustainable future.” Anderson has ballot access in CO, CT, FL, ID, LA, MI, MN, MS, NJ, NM, OR, RI, TN, UT, VT, WA (152 electoral votes) and has write-in access in AL, AK, DE, GA, IL, IO, KS, MD, MO, NE, NH, NY, PA, TX Learn more about Rocky Anderson and Justice Party on Wikipedia.

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• SQL Server: Writing CASE expressions properly when NULLs are involved

  - by Mladen Prajdic

  We’ve all written a CASE expression (yes, it’s an expression and not a statement) or two every now and then. But did you know there are actually 2 formats you can write the CASE expression in? This actually bit me when I was trying to add some new functionality to an old stored procedure. In some rare cases the stored procedure just didn’t work correctly. After a quick look it turned out to be a CASE expression problem when dealing with NULLS. In the first format we make simple “equals to” comparisons to a value: SELECT CASE <value> WHEN <equals this value> THEN <return this> WHEN <equals this value> THEN <return this> -- ... more WHEN's here ELSE <return this> END Second format is much more flexible since it allows for complex conditions. USE THIS ONE! SELECT CASE WHEN <value> <compared to> <value> THEN <return this> WHEN <value> <compared to> <value> THEN <return this> -- ... more WHEN's here ELSE <return this> END Now that we know both formats and you know which to use (the second one if that hasn’t been clear enough) here’s an example how the first format WILL make your evaluation logic WRONG. Run the following code for different values of @i. Just comment out any 2 out of 3 “SELECT @i =” statements. DECLARE @i INTSELECT  @i = -1 -- first resultSELECT  @i = 55 -- second resultSELECT  @i = NULL -- third resultSELECT @i AS OriginalValue, -- first CASE format. DON'T USE THIS! CASE @i WHEN -1 THEN '-1' WHEN NULL THEN 'We have a NULL!' ELSE 'We landed in ELSE' END AS DontUseThisCaseFormatValue, -- second CASE format. USE THIS! CASE WHEN @i = -1 THEN '-1' WHEN @i IS NULL THEN 'We have a NULL!' ELSE 'We landed in ELSE' END AS UseThisCaseFormatValue When the value of @i is –1 everything works as expected, since both formats go into the –1 WHEN branch. When the value of @i is 55 everything again works as expected, since both formats go into the ELSE branch. When the value of @i is NULL the problems become evident. The first format doesn’t go into the WHEN NULL branch because it makes an equality comparison between two NULLs. Because a NULL is an unknown value: NULL = NULL is false. That is why the first format goes into the ELSE Branch but the second format correctly handles the proper IS NULL comparison.   Please use the second more explicit format. Your future self will be very grateful to you when he doesn’t have to discover these kinds of bugs.

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• Why is 0 false?

  - by Morwenn

  This question may sound dumb, but why does 0 evaluates to false and any other [integer] value to true is most of programming languages? String comparison Since the question seems a little bit too simple, I will explain myself a little bit more: first of all, it may seem evident to any programmer, but why wouldn't there be a programming language - there may actually be, but not any I used - where 0 evaluates to true and all the other [integer] values to false? That one remark may seem random, but I have a few examples where it may have been a good idea. First of all, let's take the example of strings three-way comparison, I will take C's strcmp as example: any programmer trying C as his first language may be tempted to write the following code: if (strcmp(str1, str2)) { // Do something... } Since strcmp returns 0 which evaluates to false when the strings are equal, what the beginning programmer tried to do fails miserably and he generally does not understand why at first. Had 0 evaluated to true instead, this function could have been used in its most simple expression - the one above - when comparing for equality, and the proper checks for -1 and 1 would have been done only when needed. We would have considered the return type as bool (in our minds I mean) most of the time. Moreover, let's introduce a new type, sign, that just takes values -1, 0 and 1. That can be pretty handy. Imagine there is a spaceship operator in C++ and we want it for std::string (well, there already is the compare function, but spaceship operator is more fun). The declaration would currently be the following one: sign operator<=>(const std::string& lhs, const std::string& rhs); Had 0 been evaluated to true, the spaceship operator wouldn't even exist, and we could have declared operator== that way: sign operator==(const std::string& lhs, const std::string& rhs); This operator== would have handled three-way comparison at once, and could still be used to perform the following check while still being able to check which string is lexicographically superior to the other when needed: if (str1 == str2) { // Do something... } Old errors handling We now have exceptions, so this part only applies to the old languages where no such thing exist (C for example). If we look at C's standard library (and POSIX one too), we can see for sure that maaaaany functions return 0 when successful and any integer otherwise. I have sadly seen some people do this kind of things: #define TRUE 0 // ... if (some_function() == TRUE) { // Here, TRUE would mean success... // Do something } If we think about how we think in programming, we often have the following reasoning pattern: Do something Did it work? Yes -> That's ok, one case to handle No -> Why? Many cases to handle If we think about it again, it would have made sense to put the only neutral value, 0, to yes (and that's how C's functions work), while all the other values can be there to solve the many cases of the no. However, in all the programming languages I know (except maybe some experimental esotheric languages), that yes evaluates to false in an if condition, while all the no cases evaluate to true. There are many situations when "it works" represents one case while "it does not work" represents many probable causes. If we think about it that way, having 0 evaluate to true and the rest to false would have made much more sense. Conclusion My conclusion is essentially my original question: why did we design languages where 0 is false and the other values are true, taking in account my few examples above and maybe some more I did not think of? Follow-up: It's nice to see there are many answers with many ideas and as many possible reasons for it to be like that. I love how passionate you seem to be about it. I originaly asked this question out of boredom, but since you seem so passionate, I decided to go a little further and ask about the rationale behind the Boolean choice for 0 and 1 on Math.SE :)

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• Noob Objective-C/C++ - Linker Problem/Method Signature Problem

  - by Josh

  There is a static class Pipe, defined in C++ header that I'm including. The static method I'm interested in calling (from Objetive-c) is here: static ERC SendUserGet(const UserId &_idUser,const GUID &_idStyle,const ZoneId &_idZone,const char *_pszMsg); I have access to an objetive-c data structure that appears to store a copy of userID, and zoneID -- it looks like: @interface DataBlock : NSObject { GUID userID; GUID zoneID; } Looked up the GUID def, and its a struct with a bunch of overloaded operators for equality. UserId and ZoneId from the first function signature are #typedef GUID Now when I try to call the method, no matter how I cast it (const UserId), (UserId), etc, I get the following linker error: Ld build/Debug/Seeker.app/Contents/MacOS/Seeker normal i386 cd /Users/josh/Development/project/Mac/Seeker setenv MACOSX_DEPLOYMENT_TARGET 10.5 /Developer/usr/bin/g++-4.2 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk -L/Users/josh/Development/TS/Mac/Seeker/build/Debug -L/Users/josh/Development/TS/Mac/Seeker/../../../debug -L/Developer/Platforms/iPhoneOS.platform/Developer/usr/lib/gcc/i686-apple-darwin10/4.2.1 -F/Users/josh/Development/TS/Mac/Seeker/build/Debug -filelist /Users/josh/Development/TS/Mac/Seeker/build/Seeker.build/Debug/Seeker.build/Objects-normal/i386/Seeker.LinkFileList -mmacosx-version-min=10.5 -framework Cocoa -framework WebKit -lSAPI -lSPL -o /Users/josh/Development/TS/Mac/Seeker/build/Debug/Seeker.app/Contents/MacOS/Seeker Undefined symbols: "SocPipe::SendUserGet(_GUID const&, _GUID const&, _GUID const&, char const*)", referenced from: -[PeoplePaneController clickGet:] in PeoplePaneController.o ld: symbol(s) not found collect2: ld returned 1 exit status Is this a type/function signature error, or truly some sort of linker error? I have the headers where all these types and static classes are defined #imported -- I tried #include too, just in case, since I'm already stumbling :P Forgive me, I come from a web tech background, so this c-style memory management and immutability stuff is super hazy. Edit: Added full linker error text. Changed "function" to "method" Thanks, Josh

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• How do I filter out NaN FLOAT values in Teradata SQL?

  - by Paul Hooper

  With the Teradata database, it is possible to load values of NaN, -Inf, and +Inf into FLOAT columns through Java. Unfortunately, once those values get into the tables, they make life difficult when writing SQL that needs to filter them out. There is no IsNaN() function, nor can you "CAST ('NaN' as FLOAT)" and use an equality comparison. What I would like to do is, SELECT SUM(VAL**2) FROM DTM WHERE NOT ABS(VAL) > 1e+21 AND NOT VAL = CAST ('NaN' AS FLOAT) but that fails with error 2620, "The format or data contains a bad character.", specifically on the CAST. I've tried simply "... AND NOT VAL = 'NaN'", which also fails for a similar reason (3535, "A character string failed conversion to a numeric value."). I cannot seem to figure out how to represent NaN within the SQL statement. Even if I could represent NaN successfully in an SQL statement, I would be concerned that the comparison would fail. According to the IEEE 754 spec, NaN = NaN should evaluate to false. What I really seem to need is an IsNaN() function. Yet that function does not seem to exist.

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• Noob Objective-C/C++ - Linker Problem/Function Def Problem

  - by Josh

  There is a static class Pipe, defined in C++ header that I'm including. The function I'm interested in calling (from Objetive-c) is here: static ERC SendUserGet(const UserId &_idUser,const GUID &_idStyle,const ZoneId &_idZone,const char *_pszMsg); I have access to an objetive-c data structure that appears to store a copy of userID, and zoneID -- it looks like: @interface DataBlock : NSObject { GUID userID; GUID zoneID; } Looked up the GUID def, and its a struct with a bunch of overloaded operators for equality. UserId and ZoneId from the first function signature are #typedef GUID Now when I try to call the function, no matter how I cast it (const UserId), (UserId), etc, I get the following linker error: "Pipe::SendUserGet(_GUID const&, _GUID const&, _GUID const&, char const*)", referenced from: -[PeoplePaneController clickGet:] in PeoplePaneController.o Is this a type/function signature error, or truly some sort of linker error? I have the headers where all these types and static classes are defined #imported -- I tried #include too, just in case, since I'm already stumbling :P Forgive me, I come from a web tech background, so this c-style memory management and immutability stuff is super hazy. Thanks, Josh

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• Can't operator == be applied to generic types in C#?

  - by Hosam Aly

  According to the documentation of the == operator in MSDN, For predefined value types, the equality operator (==) returns true if the values of its operands are equal, false otherwise. For reference types other than string, == returns true if its two operands refer to the same object. For the string type, == compares the values of the strings. User-defined value types can overload the == operator (see operator). So can user-defined reference types, although by default == behaves as described above for both predefined and user-defined reference types. So why does this code snippet fail to compile? void Compare<T>(T x, T y) { return x == y; } I get the error Operator '==' cannot be applied to operands of type 'T' and 'T'. I wonder why, since as far as I understand the == operator is predefined for all types? Edit: Thanks everybody. I didn't notice at first that the statement was about reference types only. I also thought that bit-by-bit comparison is provided for all value types, which I now know is not correct. But, in case I'm using a reference type, would the the == operator use the predefined reference comparison, or would it use the overloaded version of the operator if a type defined one? Edit 2: Through trial and error, we learned that the == operator will use the predefined reference comparison when using an unrestricted generic type. Actually, the compiler will use the best method it can find for the restricted type argument, but will look no further. For example, the code below will always print true, even when Test.test<B>(new B(), new B()) is called: class A { public static bool operator==(A x, A y) { return true; } } class B : A { public static bool operator==(B x, B y) { return false; } } class Test { void test<T>(T a, T b) where T : A { Console.WriteLine(a == b); } }

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• Generating equals / hashcode / toString using annotation

  - by Bruno Bieth

  I believe I read somewhere people generating equals / hashcode / toString methods during compile time (using APT) by identifying which fields should be part of the hash / equality test. I couldn't find anything like that on the web (I might have dreamed it ?) ... That could be done like that : public class Person { @Id @GeneratedValue private Integer id; @Identity private String firstName, lastName; @Identity private Date dateOfBirth; //... } For an entity (so we want to exlude some fields, like the id). Or like a scala case class i.e a value object : @ValueObject public class Color { private int red, green, blue; } Not only the file becomes more readable and easier to write, but it also helps ensuring that all the attributes are part of the equals / hashcode (in case you add another attribute later on, without updating the methods accordingly). I heard APT isn't very well supported in IDE but I wouldn't see that as a major issue. After all, tests are mainly run by continuous integration servers. Any idea if this has been done already and if not why ? Thanks

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• How to implement Master-Detail with Multi-Selection in WPF?

  - by gehho

  Hi, I plan to create a typical Master-Detail scenario, i.e. a collection of items displayed in a ListView via DataBinding to an ICollectionView, and details about the selected item in a separate group of controls (TextBoxes, NumUpDowns...). No problem so far, actually I have already implemented a pretty similar scenario in an older project. However, it should be possible to select multiple items in the ListView and get the appropriate shared values displayed in the detail view. This means, if all selected items have the same value for a property, this value should be displayed in the detail view. If they do not share the same value, the corresponding control should provide some visual clue for the user indicating this, and no value should be displayed (or an "undefined" state in a CheckBox for example). Now, if the user edits the value, this change should be applied to all selected items. Further requirements are: MVVM compatibility (i.e. not too much code-behind) Extendability (new properties/types can be added later on) Does anyone have experience with such a scenario? Actually, I think this should be a very common scenario. However, I could not find any details on that topic anywhere. Thanks! gehho. PS: In the older project mentioned above, I had a solution using a subclass of the ViewModel which handles the special case of multi-selection. It checked all selected items for equality and returned the appropriate values. However, this approach had some drawbacks and somehow seemed like a hack because (besides other smelly things) it was necessary to break the synchronization between the ListView and the detail view and handle it manually.

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• Creating Dependencies Only to be able to Unit Test

  - by arin

  I just created a Manager that deals with a SuperClass that is extended all over the code base and registered with some sort of SuperClassManager (SCM). Now I would like to test my Manager that is aware of only the SuperClass. I tried to create a concrete SCM, however, that depends on a third party library and therefore I failed to do that in my jUnit test. Now the option is to mock all instances of this SCM. All is good until now, however, when my Manager deals with the SCM, it returns children of the SuperClass that my Manager does not know or care about. Nevertheless, the identities of these children are vital for my tests (for equality, etc.). Since I cannot use the concrete SCM, I have to mock the results of calls to the appropriate functions of the SCM, however, this means that my tests and therefore my Manager need to know and care about the children of the SuperClass. Checking the code base, there does not seem to be a more appropriate location for my test (that already maintains the appropriate real dependencies). Is it worth it to introduce unnecessary dependencies for the sake of unit testing?

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• How is the 'is' keyword implemented in Python?

  - by Srikanth

  ... the is keyword that can be used for equality in strings. >>> s = 'str' >>> s is 'str' True >>> s is 'st' False I tried both __is__() and __eq__() but they didn't work. >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __is__(self, s): ... return self.s == s ... >>> >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work False >>> >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __eq__(self, s): ... return self.s == s ... >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work, but again failed False >>> Thanks for your help!

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• Resolving Circular References for Objects Implementing ISerializable

  - by Chris

  I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

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• how to refer to the current struct in an overloaded operator?

  - by genesys

  Hi! I have a struct for which i want to define a relative order by defining < , , <= and = operators. actually in my order there won't be any equality, so if one struct is not smaller than another, it's automatically larger. I defined the first operator like this: struct MyStruct{ ... ... bool operator < (const MyStruct &b) const {return (somefancycomputation);} }; now i'd like to define the other operators based on this operator, such that <= will return the same as < and the other two will simply return the oposite. so for example for the operator i'd like to write something like bool operator > (const MyStruct &b) const {return !(self<b);} but i don't know how to refere to this 'self' since i can refere only to the fields inside the current struct. whole is in C++ hope my question was understandable :) thank you for the help!

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• How to tell if you touched a CCLabel? (Cocos2d Question)

  - by RexOnRoids

  How to tell if you touched a CCLabel? The following code obviously does not work well enough because it only tests for point equality. Naturally touch point will not necessarily be equal to the position property of the CCLabel (CCNode). How to I tell if a Touch point has fallen within the "rectangle?" of the CCLabel? - (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { for( UITouch *touch in touches ) { CGPoint location = [touch locationInView: [touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; self.myGraphManager.isSliding = NO; if(CGPointEqualToPoint(location, label1.position)){ NSLog(@"Label 1 Touched"); }else if(CGPointEqualToPoint(location, label2.position)){ NSLog(@"Label 2 Touched"); }else if(CGPointEqualToPoint(location, label3.position)){ NSLog(@"Label 3 Touched"); }else if(CGPointEqualToPoint(location, label4.position)){ NSLog(@"Label 4 Touched"); }else if(CGPointEqualToPoint(location, label5.position)){ NSLog(@"Label 5 Touched"); }else if(CGPointEqualToPoint(location, label6.position)){ NSLog(@"Label 6 Touched"); } NSLog(@"Touch Made!"); } }

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• How can I filter a Perl DBIx recordset with 2 conditions on the same column?

  - by BrianH

  I'm getting my feet wet in DBIx::Class - loving it so far. One problem I am running into is that I want to query records, filtering out records that aren't in a certain date range. It took me a while to find out how to do a "<=" type of match instead of an equality match: my $start_criteria = ">= $start_date"; my $end_criteria = "<= $end_date"; my $result = $schema->resultset('MyTable')->search( { 'status_date' => \$start_criteria, 'status_date' => \$end_criteria, }); The obvious problem with this is that since the filters are in a hash, I am overwriting the value for "status_date", and am only searching where the status_date <= $end_date. The SQL that gets executed is: SELECT me.* from MyTable me where status_date <= '9999-12-31' I've searched CPAN, Google and SO and haven't been able to figure out how to apply 2 conditions to the same column. All documentation I've been able to find shows how to filter on more than 1 column, but not 2 conditions on the same column. I'm sure I'm missing something obvious - hoping someone here can point it out to me? Thanks in advance! Brian

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