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  • Why doesn't C have rotate left/right operators?

    - by icepack
    A bit of a philosophical question, I suppose. Hope it belongs here. C language has the standard set of bit-wise operations, including OR, AND, XOR, SHIFT LEFT/RIGHT, NOT. Anyone has an idea why rotate left/rotate right isn't included in the language? These operators are of the same complexity as other bit-wise operators and normally require a single assembly instruction, like the others. Besides, I can think of a lot of uses for rotate operator, probably not less than, say, xor operator - so it sounds a bit strange to me that they aren't included in C along with the rest. Edit: Please stop suggesting implementations of rotation operators. I know how to do that and it's not what the question about.

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  • Iterator for second to last element in a list

    - by BSchlinker
    I currently have the following for loop: for(list<string>::iterator jt=it->begin(); jt!=it->end()-1; jt++) I have a list of strings which is in a larger list (list<list<string> >). I want to loop through the contents of the innerlist until I get to the 2nd to last element. This is because I have already processed the contents of the final element, and have no reason to process them again. However, using it->end()-1 is invalid -- I cannot use the - operator here. While I could use the -- operator, this would decrement this final iterator on each cycle. I believe a STL list is a doubly linked list, so from my perspective, it should be possible to do this. Advice? Thanks in advance

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  • Copying a Polymorphic object in C++

    - by doron
    I have base-class Base from which is derived Derived1, Derived2 and Derived3. I have constructed an instance for one of the the derived classes which I store as Base* a. I now need to make a deep copy of the object which I will store as Base* b. As far as I know, the normal way of copying a class is to use copy constructors and to overload operator=. However since I don't know whether a is of type Derived1, Derived2 or Derived3, I cannot think of a way of using either the copy constructor or operator=. The only way I can think of to cleanly make this work is to implement something like: class Base { public: virtual Base* Clone() = 0; }; and the implement Clone in in the derived class as in: class Derivedn : public Base { public: Base* Clone() { Derived1* ret = new Derived1; copy all the data members } }; Java tends to use Clone quite a bit is there more of a C++ way of doing this?

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  • Aquamacs and IDLWAVE

    - by nicolavianello
    I've just installed the new Aquamacs 2.0 in my Mac Os X 10.6.3 and I'm an happy user of IDLWAVE on Aquamacs for programming in IDL. Unfortunately I run into a problem which I can't understand. I used in my configuration file to put the following (setq idlwave-surround-by-blank t) for the beautiful space around operator. This used to work till Aquamacs 2.0 preview b3 (third beta release) from that on, it stops to work and every time I type an operator (the same for '=' '<' '' etc) I got the following message Debugger entered--Lisp error: (void-variable idlwave-expand-equal) (lambda nil (interactive) (self-insert-command 1) idlwave-expand- equal -1 -1)() call-interactively((lambda nil (interactive) (self-insert-command 1) idlwave-expand-equal -1 -1) nil nil) Any help is welcommed

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  • R: How can I use apply on rows of a data.frame and get out $column_name?

    - by John
    I'm trying to access $a using the following example: df<-data.frame(a=c("x","x","y","y"),b=c(1,2,3,4)) > df a b 1 x 1 2 x 2 3 y 3 4 y 4 test_fun <- function (data.frame_in) { print (data.frame_in[1]) } I can now access $a if I use an index for the first column: apply(df, 1, test_fun) a "x" a "x" a "y" a "y" [1] "x" "x" "y" "y" But I cannot access column $a with the $ notation: error: "$ operator is invalid for atomic vectors" test_fun_2 <- function (data.frame_in) { print (data.frame_in$a) } >apply(df, 1, test_fun_2) Error in data.frame_in$a : $ operator is invalid for atomic vectors Is this not possible?

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  • converting string to int in C++

    - by xbonez
    I am trying to convert a string I read in from a file to an int value so I can store it in an integer variable. This is what my code looks like: ifstream sin; sin.open("movie_output.txt"); string line; getline(sin,line); myMovie.setYear(atoi(line)); Over here, setYear is a mutator in the Movie class (myMovie is an object of Movie class) that looks like this: void Movie::setYear(unsigned int year) { year_ = year; } When I run the code, I get the following error: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

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  • Silencing GCC warnings when using an "Uncopyable" class

    - by Kazade
    I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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  • Help translating Reflector deconstruction into compilable code

    - by code poet
    So I am Reflector-ing some framework 2.0 code and end up with the following deconstruction fixed (void* voidRef3 = ((void*) &_someMember)) { ... } This won't compile due to 'The right hand side of a fixed statement assignment may not be a cast expression' I understand that Reflector can only approximate and generally I can see a clear path but this is a bit outside my experience. Question: what is Reflector trying to describe to me? Update: Am also seeing the following fixed (IntPtr* ptrRef3 = ((IntPtr*) &this._someMember)) Update: So, as Mitch says, it is not a bitwise operator, but an addressOf operator. Question is now: fixed (IntPtr* ptrRef3 = &_someMember) fails with an 'Cannot implicitly convert type 'xxx*' to 'System.IntPtr*'. An explicit conversion exists (are you missing a cast?)' compilation error. So I seemed to be damned if I do and damned if I dont. Any ideas?

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  • Which style is preferable when writing this boolean expression?

    - by Jeppe Stig Nielsen
    I know this question is to some degree a matter of taste. I admit this is not something I don't understand, it's just something I want to hear others' opinion about. I need to write a method that takes two arguments, a boolean and a string. The boolean is in a sense (which will be obvious shortly) redundant, but it is part of a specification that the method must take in both arguments, and must raise an exception with a specific message text if the boolean has the "wrong" value. The bool must be true if and only if the string is not null or empty. So here are some different styles to write (hopefully!) the same thing. Which one do you find is the most readable, and compliant with good coding practice? // option A: Use two if, repeat throw statement and duplication of message string public void SomeMethod(bool useName, string name) { if (useName && string.IsNullOrEmpty(name)) throw new SomeException("..."); if (!useName && !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option B: Long expression but using only && and || public void SomeMethod(bool useName, string name) { if (useName && string.IsNullOrEmpty(name) || !useName && !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option C: With == operator between booleans public void SomeMethod(bool useName, string name) { if (useName == string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } // option D1: With XOR operator public void SomeMethod(bool useName, string name) { if (!(useName ^ string.IsNullOrEmpty(name))) throw new SomeException("..."); // rest of method } // option D2: With XOR operator public void SomeMethod(bool useName, string name) { if (useName ^ !string.IsNullOrEmpty(name)) throw new SomeException("..."); // rest of method } Of course you're welcome to suggest other possibilities too. Message text "..." would be something like "If 'useName' is true a name must be given, and if 'useName' is false no name is allowed".

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  • Checking for uppercase/lowercase/numbers with Jquery

    - by user1725794
    Either I'm being really retarded here or its just the lack of sleep but why doesn't this work? If I use the "or" operator it works for each separate test but as soon as it change it to the "and" operator it stops working. I'm trying to test the password input of a form to see if its contains lowercase, uppercase and at least 1 number of symbol. I'm having a lot of trouble with this so help would be lovely, here is the code I have. var upperCase= new RegExp('[^A-Z]'); var lowerCase= new RegExp('[^a-z]'); var numbers = new RegExp('[^0-9]'); if(!$(this).val().match(upperCase) && !$(this).val().match(lowerCase) && !$(this).val().match(numbers)) { $("#passwordErrorMsg").html("Your password must be between 6 and 20 characters. It must contain a mixture of upper and lower case letters, and at least one number or symbol."); } else { $("#passwordErrorMsg").html("OK") }

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  • NHibernate - define where condition

    - by t.kehl
    Hi. In my application the user can defines search-conditions. He can choose a column, set an operator (equals, like, greater than, less or equal than, etc.) and give in the value. After the user clicks on a button and the application should do a search on the database with the condition. I use NHibernate and ask me now, what is the efficientest way to do this with NHibernate. Should I create a query with it like (Column=Name, Operator=Like, Value=%John%) var a = session.CreateCriteria<Customer>(); a.Add(Restrictions.Like("Name", "%John%")); return a.List<Customer>(); Or should I do this with HQL: var q = session.CreateQuery("from Customer where " + where); return q.List<Customer >(); Or is there a more bether solution? Thanks for your help. Best Regards, Thomas

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  • Python scope problems only when _assigning_ to a variable

    - by wallacoloo
    So I'm having a very strange error right now. I found where it happens, and here's the simplest code that can reproduce it. def parse_ops(str_in): c_type = "operator" def c_dat_check_type(t): print c_type #c_type = t c_dat_check_type("number") >>> parse_ops("12+a*2.5") If you run it as-is, it prints "operator". But if you uncomment that line, it gives an error: Traceback (most recent call last): File "<pyshell#212>", line 1, in <module> parse_ops("12+a*2.5") File "<pyshell#211>", line 7, in parse_ops c_dat_check_type("number") File "<pyshell#211>", line 4, in c_dat_check_type print c_type UnboundLocalError: local variable 'c_type' referenced before assignment Notice the error occurs on the line that worked just fine before. Any ideas what causes this and how I can fix this? I'm using Python 2.6.1.

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  • help in compare validate in c#

    - by scatman
    i have 2 textboxes that i am filling with StartDate, and Endate. i want to use the compareValidator to make sure that the StartDate is less that the EndDate. i used this: <asp:CompareValidator ID="Comp" ControlToValidate="txtStartDate" ControlToCompare="txtEndDate" Operator="LessThan" Type="Date" runat="server" Display="dynamic" Text="Failed!" /> the validator is always giving me Failed no matter what the dates are. if startdateendate or vise versa, Failed appears. i am using (MM/dd/yyyy) format in the textboxes. EDIT: ok i solved the problem. if anyone interested here is the new comparevalidator: <asp:CompareValidator ID="Comp" ControlToValidate="txtEndDate" ControlToCompare="txtStartDate" Operator="GreaterThan" Type="Date" runat="server" Display="dynamic" Text="Failed!" />

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  • How to get this to compile?

    - by ShaChris23
    I have this code which compiles and works as expected: class Right {}; class Left { public: Left& operator = (Right const&) { //... Do something ... return *this; } }; int main() { Right right; Left left; // Assign individual object -- this works left = right; } But now, this one surprises me, I thought the template would work itself out since I already provided the = operator() to the Left class. int main() { ... std::list<Right> rightLst; std::list<Left> leftLst; // Assign a list of objects -- this doesn't compile leftLst = rightLst; } What can I do so that I could convert the rightLst to leftLst conversion in a single line?

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  • Maps with a nested vector

    - by wawiti
    For some reason the compiler won't let me retrieve the vector of integers from the map that I've created, I want to be able to overwrite this vector with a new vector. The error the compiler gives me is ridiculous. Thanks for your help!! The compiler didn't like this part of my code: line_num = miss_words[word_1]; Error: [Wawiti@localhost Lab2]$ g++ -g -Wall *.cpp -o lab2 main.cpp: In function ‘int main(int, char**)’: main.cpp:156:49: error: no match for ‘operator=’ in ‘miss_words.std::map<_Key, _Tp, _Compare, _Alloc>::operator[]<std::basic_string<char>, std::vector<int>, std::less<std::basic_string<char> >, std::allocator<std::pair<const std::basic_string<char>, std::vector<int> > > >((*(const key_type*)(& word_1))) = line_num.std::vector<_Tp, _Alloc>::push_back<int, std::allocator<int> >((*(const value_type*)(& line)))’ main.cpp:156:49: note: candidate is: In file included from /usr/lib/gcc/x86_64-redhat->linux/4.7.2/../../../../include/c++/4.7.2vector:70:0, from header.h:19, from main.cpp:15: /usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/bits/vector.tcc:161:5: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(const std::vector<_Tp, _Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>] /usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/bits/vector.tcc:161:5: note: no known conversion for argument 1 from ‘void’ to ‘const std::vector<int>&’ CODE: map<string, vector<int> > miss_words; // Creates a map for misspelled words string word_1; // String for word; string sentence; // To store each line; vector<int> line_num; // To store line numbers ifstream file; // Opens file to be spell checked file.open(argv[2]); int line = 1; while(getline(file, sentence)) // Reads in file sentence by sentence { sentence=remove_punct(sentence); // Removes punctuation from sentence stringstream pars_sentence; // Creates stringstream pars_sentence << sentence; // Places sentence in a stringstream while(pars_sentence >> word_1) // Picks apart sentence word by word { if(dictionary.find(word_1)==dictionary.end()) { line_num = miss_words[word_1]; //Compiler doesn't like this miss_words[word_1] = line_num.push_back(line); } } line++; // Increments line marker }

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  • C++ enumeration

    - by asli
    Hi,my question is about enumeration,my codes are : #include<iostream> using namespace std; int main() { enum bolumler {programcilik,donanim,muhasebe,motor,buro} bolum; bolum = donanim; cout << bolum << endl; bolum += 2; // bolum=motor cout << bolum; return 0; } The output should be 1 3 but according to these codes the error is: error C2676: binary '+=' : 'enum main::bolumler' does not define this operator or a conversion to a type acceptable to the predefined operator Error executing cl.exe. 111.obj - 1 error(s), 0 warning(s) Can you help me ?The other question is what can I do if I want to see the output like that "muhasebe"?

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  • Would this constructor be acceptable practice?

    - by Robb
    Let's assume I have a c++ class that have properly implemented a copy constructor and an overloaded = operator. By properly implemented I mean they are working and perform a deep copy: Class1::Class1(const Class1 &class1) { // Perform copy } Class1& Class1::operator=(const Class1 *class1) { // perform copy return *this; } Now lets say I have this constructor as well: Class1::Class1(Class1 *class1) { *this = *class1; } My question is would the above constructor be acceptable practice? This is code that i've inherited and maintaining.

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  • distinguishing a string with flex

    - by haluk
    Hi, I need to tokenize some strings which will be splitted of according to operators like = and !=. I was successful using regex until the string has != operator. In my case, string was seperated into two parts, which is expected but ! mark is in the left side even it is part of given operator. Therefore, I believe that regex is not suitable for it and I want to benefit from lex. Since I do not have enough knowledge and experience with lex, I am not sure whether it fits my work or not. Basically, I am trying to do replace the right hand side of the operators with actual values from other data. Do you people think that can it be helpful for my case? Thanks.

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  • UrlRewriteFilter Direct to https

    - by adi
    I am using UrlRewriteFilter to redirect to SSL. I am running Glassfishv2. My rule looks something like this now. It's in my urlrewrite.xml in WEB-INF of my war folder. Is there any other glassfish setting that needs to be set? <rule> <condition name="host" operator="notequal">https://abc.def.com</condition> <condition name="host" operator="notequal">^$</condition> <from>^/(.*)</from> <to type="permanent-redirect" last="true">https://abc.def.com/ghi/$1</to> </rule> But FF keeps saying that the URL redirect rule is in a way that it will never complete. I am not exactly sure whats happening here. any ideas?

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  • C++ Why is the copy constructor implicitly called?

    - by ShaChris23
    Why is the Child class's copy constructor called in the code below? I mean, it automatically converts Base to Child via the Child copy constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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  • typeof === "undefined" vs. != null

    - by Thor Thurn
    I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. It's needed because 'undefined' could be renamed, though. My question is: How is that code any better than this approach: if (input != null) { // do stuff } As far as I know, you can't redefine null, so it's not going to break unexpectedly. And, because of the type-coercion of the != operator, this checks for both undefined and null... which is often exactly what you want (e.g. for optional function parameters). Yet this form does not seem widespread, and it even causes JSLint to yell at you for using the evil != operator. Why is this considered bad style?

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