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  • are C functions declared in <c____> headers guaranteed to be in the global namespace as well as std?

    - by Evan Teran
    So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); } EDIT: The closest I've found is this (17.4.1.2p4): Except as noted in clauses 18 through 27, the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C (Clause 7), or ISO/IEC:1990 Programming Languages—C AMENDMENT 1: C Integrity, (Clause 7), as appropriate, as if by inclusion. In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std. which to be honest I could interpret either way. "the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C" tells me that they may be required in the global namespace, but "In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std." says they are in std (but doesn't specify any other scoped they are in).

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  • How to flatten list of options using higher order functions?

    - by Synesso
    Using Scala 2.7.7: If I have a list of Options, I can flatten them using a for-comprehension: val listOfOptions = List(None, Some("hi"), None) listOfOptions: List[Option[java.lang.String]] = List(None, Some(hi), None) scala> for (opt <- listOfOptions; string <- opt) yield string res0: List[java.lang.String] = List(hi) I don't like this style, and would rather use a HOF. This attempt is too verbose to be acceptable: scala> listOfOptions.flatMap(opt => if (opt.isDefined) Some(opt.get) else None) res1: List[java.lang.String] = List(hi) Intuitively I would have expected the following to work, but it doesn't: scala> List.flatten(listOfOptions) <console>:6: error: type mismatch; found : List[Option[java.lang.String]] required: List[List[?]] List.flatten(listOfOptions) Even the following seems like it should work, but doesn't: scala> listOfOptions.flatMap(_: Option[String]) <console>:6: error: type mismatch; found : Option[String] required: (Option[java.lang.String]) => Iterable[?] listOfOptions.flatMap(_: Option[String]) ^ The best I can come up with is: scala> listOfOptions.flatMap(_.toList) res2: List[java.lang.String] = List(hi) ... but I would much rather not have to convert the option to a list. That seems clunky. Any advice?

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  • Should every code for the Wordpress plgins be included in the functions and hooked with the Wordpres

    - by Chetan sharma
    I just started the Plugin development for the Wordpress, but finding it little difficult to understand. Looks like everything should be hooked with the wordpess to get it run and moreover are there all the global variables that i need to use. I am making a video plugin and designed some of the forms and display page, but didn't went through the templates, is it compulsory to follow the template structure or we can design our on layout. I am pretty much confused about all this. Can someone explain a little. Thanks.

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  • Is there a website to lookup already common code functions?

    - by pinnacler
    I'm sitting here writing a function that I'm positive has been written before, somewhere on earth. It's just too common to have not been attempted, and I'm wondering why I can't just go to a website and search for a function that I can then copy and paste into my project in 2 seconds, instead of wasting my day reinventing the wheel. Sure there are certain libraries you can use, but where do you find these libraries and when they are absent, is there a site like I'm describing?

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  • How to unit tests functions which return results asyncronously in XCode?

    - by DevDevDev
    I have something like - (void)getData:(SomeParameter*)param { // Remotely call out for data returned asynchronously // returns data via a delegate method } - (void)handleDataDelegateMethod:(NSData*)data { // Handle returned data } I want to write a unit test for this, how can I do something better than NSData* returnedData = nil; - (void)handleDataDelegateMethod:(NSData*)data { returnedData = data; } - (void)test { [obj getData:param]; while (!returnedData) { [NSThread sleep:1]; } // Make tests on returnedData }

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  • How do I read from a file consists of city names and coordinates/Populations and create functions to get the coordinates and population?

    - by Braybray
    I'm using Python, and I have a file which has city names and information such as names, coordinates of the city and population of the city: Youngstown, OH[4110,8065]115436 Yankton, SD[4288,9739]12011 966 Yakima, WA[4660,12051]49826 1513 2410 Worcester, MA[4227,7180]161799 2964 1520 604 Wisconsin Dells, WI[4363,8977]2521 1149 1817 481 595 How can I create a function to take the city name and return a list containing the latitude and longitude of the given city? fin = open ("miles.dat","r") def getCoordinates cities = [] for line in fin: cities.append(line.rstrip()) for word in line: print line.split() That's what I tried now; how could I get the coordinates of the city by calling the names of the city and how can I return the word of each line but not letters? Any help will be much appreciated, thanks all.

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  • What is the best practice when coding math class/functions ?

    - by Isaac Clarke
    Introductory note : I voluntarily chose a wide subject. You know that quote about learning a cat to fish, that's it. I don't need an answer to my question, I need an explanation and advice. I know you guys are good at this ;) Hi guys, I'm currently implementing some algorithms into an existing program. Long story short, I created a new class, "Adder". An Adder is a member of another class representing the physical object actually doing the calculus , which calls adder.calc() with its parameters (merely a list of objects to do the maths on). To do these maths, I need some parameters, which do not exist outside of the class (but can be set, see below). They're neither config parameters nor members of other classes. These parameters are D1 and D2, distances, and three arrays of fixed size : alpha, beta, delta. I know some of you are more comfortable reading code than reading text so here you go : class Adder { public: Adder(); virtual Adder::~Adder(); void set( float d1, float d2 ); void set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ); // Snipped prototypes float calc( List& ... ); // ... inline float get_d1() { return d1_ ;}; inline float get_d2() { return d2_ ;}; private: float d1_; float d2_; int alpha_[N_MAX]; // A #define N_MAX is done elsewhere int beta_[N_MAX]; int delta_[N_MAX]; }; Since this object is used as a member of another class, it is declared in a *.h : private: Adder adder_; By doing that, I couldn't initialize the arrays (alpha/beta/delta) directly in the constructor ( int T[3] = { 1, 2, 3 }; ), without having to iterate throughout the three arrays. I thought of putting them in static const, but I don't think that's the proper way of solving such problems. My second guess was to use the constructor to initialize the arrays Adder::Adder() { int alpha[N_MAX] = { 0, -60, -120, 180, 120, 60 }; int beta[N_MAX] = { 0, 0, 0, 0, 0, 0 }; int delta[N_MAX] = { 0, 0, 180, 180, 180, 0 }; set( 2.5, 0, alpha, beta, delta ); } void Adder::set( float d1, float d2 ) { if (d1 > 0) d1_ = d1; if (d2 > 0) d2_ = d2; } void Adder::set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ) { set( d1, d2 ); for (int i = 0; i < N_MAX; ++i) { alpha_[i] = alpha[i]; beta_[i] = beta[i]; delta_[i] = delta[i]; } } My question is : Would it be better to use another function - init() - which would initialize arrays ? Or is there a better way of doing that ? My bonus question is : Did you see some mistakes or bad practice along the way ?

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  • C++ and C#, "Casting" Functions to Delegates, What's the scoop?

    - by Jacob G
    In C# 2.0, I can do the following: public class MyClass { delegate void MyDelegate(int myParam); public MyClass(OtherObject obj) { //THIS IS THE IMPORTANT PART obj.SomeCollection.Add((MyDelegate)MyFunction); } private void MyFunction(int myParam); { //... } } Trying to implement the same thing in C++, it appears I have to do: MyDelegate del = gcnew MyDelegate(this, MyFunction); obj-SomeCollection-Add(del); Obviously I can create a new instance of the delegate in C# as well instead of what's going on up there. Is there some kind of magic going on in the C# world that doesn't exist in C++ that allows that cast to work? Some kind of magic anonymous delegate? Thanks.

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  • question about c++ template functions taking any type as long that type meets at least one of the re

    - by smerlin
    Since i cant explain this very well, i will start with a small example right away: template <class T> void Print(const T& t){t.print1();} template <class T> void Print(const T& t){t.print2();} This does not compile: error C2995: 'void Print(const T &)' : function template has already been defined So, how can i create a template function which takes any type T as long as that type has a print1 memberfunction OR a print2 memberfunction (no polymorphism) ?

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  • Is this considered as using private functions in iPhone dev, and thus illegal?

    - by user153231
    I'm trying to disable scrolling for a UIWebView and the only way i found is using this way: #import <objc/runtime.h> id scroller = [[Webview subviews] lastObject]; int count; Method *method = class_copyMethodList([scroller class], &count); int i; for (i=0; i<count; i++) { if (strcmp(method_getName(method[i]), "setScrollingEnabled:") == 0) break; } IMP test = method_getImplementation(method[i]); test(scroller, @selector(setScrollingEnabled:), NO); Is this considered to be an illegal way of using the iPhone SDK? Can this cause my application to be rejected for the App store?

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  • Python: how to run several scripts (or functions) at the same time under windows 7 multicore processor 64bit

    - by Gianni
    sorry for this question because there are several examples in Stackoverflow. I am writing in order to clarify some of my doubts because I am quite new in Python language. i wrote a function: def clipmyfile(inFile,poly,outFile): ... # doing something with inFile and poly and return outFile Normally I do this: clipmyfile(inFile="File1.txt",poly="poly1.shp",outFile="res1.txt") clipmyfile(inFile="File2.txt",poly="poly2.shp",outFile="res2.txt") clipmyfile(inFile="File3.txt",poly="poly3.shp",outFile="res3.txt") ...... clipmyfile(inFile="File21.txt",poly="poly21.shp",outFile="res21.txt") I had read in this example Run several python programs at the same time and i can use (but probably i wrong) from multiprocessing import Pool p = Pool(21) # like in your example, running 21 separate processes to run the function in the same time and speed my analysis I am really honest to say that I didn't understand the next step. Thanks in advance for help and suggestion Gianni

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  • In Python, are there builtin functions for elementwise boolean operators over boolean lists?

    - by bshanks
    For example, if you have n lists of bools of the same length, then elementwise boolean AND should return another list of that length that has True in those positions where all the input lists have True, and False everywhere else. It's pretty easy to write, i just would prefer to use a builtin if one exists (for the sake of standardization/readability). Here's an implementation of elementwise AND: def eAnd(*args): return [all(tuple) for tuple in zip(*args)] example usage: >>> eAnd([True, False, True, False, True], [True, True, False, False, True], [True, True, False, False, True]) [True, False, False, False, True] thx

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  • Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

    - by Markus
    I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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  • JPA and aggregate functions. How do I use the result of the query?

    - by Bogdan
    Hey guys, I'm new to ORM stuff and I need some help understanding something. Let's assume I have the following standard SQL query: SELECT *, COUNT(test.testId) AS noTests FROM inspection LEFT JOIN test ON inspection.inspId = test.inspId GROUP BY inspection.inspId which I want to use in JPA. I have an Inspection entity with a one-to-many relationship to a Test entity. (an inspection has many tests) I tried writing this in JPQL: Query query = em.createQuery("SELECT insp, COUNT(???what???) FROM Inspection insp LEFT JOIN insp.testList " + "GROUP BY insp.inspId"); 1) How do I write the COUNT clause? I'd have to apply count to elements from the test table but testList is a collection, so I can't do smth like COUNT(insp.testList.testId) 2) Assuming 1 is resolved, what type of object will be returned. It will definitely not be an Inspection object... How do I use the result?

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  • Where should I put common utility functions for Perl .t tests?

    - by zedoo
    I am getting started with Test::More, already have a few .t test scripts. Now I'd like to define a function that will only be used for the tests, but across different .t files. Where's the best place to put such a function? Define another .t without any tests and require it where needed? (As a sidenote I use the module structure created by Module::Starter)

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  • Best way to carry & modify a variable through various instances and functions?

    - by bobsoap
    I'm looking for the "best practice" way to achieve a message / notification system. I'm using an OOP-based approach for the script and would like to do something along the lines of this: if(!$something) $messages->add('Something doesn\'t exist!'); The add() method in the messages class looks somewhat like this: class messages { public function add($new) { $messages = $THIS_IS_WHAT_IM_LOOKING_FOR; //array $messages[] = $new; $THIS_IS_WHAT_IM_LOOKING_FOR = $messages; } } In the end, there is a method in which reads out $messages and returns every message as nicely formatted HTML. So the questions is - what type of variable should I be using for $THIS_IS_WHAT_IM_LOOKING_FOR? I don't want to make this use the database. Querying the db every time just for some messages that occur at runtime and disappear after 5 seconds just seems like overkill. Using global constants for this is apparently worst practice, since constants are not meant to be variables that change over time. I don't even know if it would work. I don't want to always pass in and return the existing $messages array through the method every time I want to add a new message. I even tried using a session var for this, but that is obviously not suited for this purpose at all (it will always be 1 pageload too late). Any suggestions? Thanks!

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  • Real world examples of Ecmascript functions returning a Reference?

    - by Bergi
    Read the EcmaScript specification, section 8.7 The Reference Specification Type: The Reference type is used to explain the behaviour of such operators as delete, typeof, and the assignment operators. […] A Reference is a resolved name binding. Function calls are permitted to return references. This possibility is admitted purely for the sake of host objects. No built-in ECMAScript function defined by this specification returns a reference and there is no provision for a user-defined function to return a reference. Those last two sentences impressed me. With this, you could do things like coolHostFn() = value (valid syntax, btw). So my question is: Are there any EcmaScript implementations that define host function objects which result in Reference values?

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  • C++, generic programming and virtual functions. How do I get what I want?

    - by carleeto
    This is what I would like to do using templates: struct op1 { virtual void Method1() = 0; } ... struct opN { virtual void MethodN() = 0; } struct test : op1, op2, op3, op4 { virtual void Method1(){/*do work1*/}; virtual void Method2(){/*do work2*/}; virtual void Method3(){/*do work3*/}; virtual void Method4(){/*do work4*/}; } I would like to have a class that simply derives from a template class that provides these method declarations while at the same time making them virtual. This is what I've managed to come up with: #include <iostream> template< size_t N > struct ops : ops< N - 1 > { protected: virtual void DoStuff(){ std::cout<<N<<std::endl; }; public: template< size_t i > void Method() { if( i < N ) ops<i>::DoStuff(); } //leaving out compile time asserts for brevity } struct test : ops<6> { }; int main( int argc, char ** argv ) { test obj; obj.Method<3>(); //prints 3 return 0; } However, as you've probably guessed, I am unable to override any of the 6 methods I have inherited. I'm obviously missing something here. What is my error? No, this isn't homework. This is curiosity.

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  • Some stupid warnings

    - by thetna
    I have a number of C source files(both .c and .h files). header files contains a number of functions. Out of those functions, only partially are used in a source .C file.Suppose a.h,b.h are header files and a.c and b.c are .c files. a.h is included in a.c. But only a number of functions those are in a. h are used and rest are not used. After compilation I find following warnings: function XXXX defined but not used. But those XXXX functions which are not used in a.c are used in b.c. So, i can't completely remove those functions too. So , i decided to make a separate file containing only those XXXX functions and included it wherever it is used.Doing this is creating multiple number of header files. Can anybody please suggest me to some effective way to solve this problem.

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