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  • Prevent Erroneous Property Assignment

    - by Gordon
    Porting android applications to iphone applications always gives me the following pattern that I accidentally create: - (void) myFunc:(id)prop { self.property = property; } Which instead should be: - (void) myFunc:(id)prop { self.property = prop; } This always causes my program to quietly break because property gets reset to its existing value rather than being set to the new value, 'prop'. I cannot name the parameter 'prop' to 'property' since the compile complains that the parameter masks the instance variables visibility. Is there a good way to avoid this situation? There are no compiler warnings. Is there a way to make xcode prevent this? I cannot see very many situations where you would set a property to the value of its underlying instance variable (maybe to trigger a KVO binding?), but I don't see myself doing that in majority of cases. I understand the above code is synthetic and should be done with @synthesize, but I am just using it as a simplified example to illustrate my point.

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  • javascript var assignment conversion to target type

    - by pbhd
    searching for a function, which converts rhs to the type of lhs. e.g. var x=false // x is boolean now; x=assign (x, "true"); //should convert "true" to boolean and return that x=assign (x, 1); // dto, convert 1 to true x=0 // x is number x=assign (x, "123"); // should convert "123" to 123; so such a function can be written, thats not the question. But: Is there somewhere a somehow complete implementation of such a thing? I started with something like that: function assign (v, x) { if (typeof v==typeof x) { return x; } switch (typeof v) { case 'boolean' : { return x=='true'?true:false; } case 'number' : { return parseFloat(x); } } return "xxx"; } var v=true; var x='true'; var r1=assign (v, x); console.log (typeof r1+ " "+r1); v=10; x="123"; var r1=assign (v, x); console.log (typeof r1+ " "+r1); which of course is not complete, but maybe shows what I'm goig for.

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  • Any method to denote object assignment?

    - by Droogans
    I've been studying magic methods in Python, and have been wondering if there's a way to outline the specific action of: a = MyClass(*params).method() versus: MyClass(*params).method() In the sense that, perhaps, I may want to return a list that has been split on the '\n' character, versus dumping the raw list into the variable a that keeps the '\n' intact. Is there a way to ask Python if its next action is about to return a value to a variable, and change action, if that's the case? I was thinking: class MyClass(object): def __init__(*params): self.end = self.method(*params) def __asgn__(self): return self.method(*params).split('\n') def __str__(self): """this is the fallback if __asgn__ is not called""" return self.method(*params)

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  • cant figure out pointer assignment in c

    - by vadiklk
    int add(char *var1, char *var2, char **var3) { int num1, num2, length1 = strlen(var1), length2 = strlen(var2), length = max(length1, length2) + 1; char *result = (char*) calloc(length, sizeof(char)); ... free(*var3); *var3 = result; return 0; } out side of the function i get its still nothing(var3); more detail: int addSubCommand(char **vars, int isAdd) { ... return add(vars[index1], var2, &(vars[index3])); } that's where i call add. the char** vars goes from every function to the other.

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  • Subtyping and assignment in Java

    - by Danrex
    Arghh I just know people are going to hate me for asking this... I was just playing around with inheritance and I noticed you can instantiate a subclass object in one of two ways when you write code. So then I wondered if there is any functional difference between these two methods. So in the code below, does this produce the exact same result...a MountainBike object, or is there some difference I should know about? Bicycle is the superclass for this example. If I do Bicycle bike or MountainBike bike I am effectively making a MountainBike due to new MountainBike()? So basically the difference is just semantics at this point? Bicycle bike = new MountainBike(); MountainBike bike = new MountainBike();

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  • Saving a select count(*) value to an integer (SQL Server)

    - by larryq
    Hi everyone, I'm having some trouble with this statement, owing no doubt to my ignorance of what is returned from this select statement: declare @myInt as INT set @myInt = (select COUNT(*) from myTable as count) if(@myInt <> 0) begin print 'there's something in the table' end There are records in myTable, but when I run the code above the print statement is never run. Further checks show that myInt is in fact zero after the assignment above. I'm sure I'm missing something, but I assumed that a select count would return a scalar that I could use above?

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  • Problem with assigning elements of a class array to individual variables in MATLAB

    - by Marc
    This is a bit of a duplicate of this question, this question, and this question, however those solutions don't work, so I'm asking mine. I've got an array of locally defined classes and I'd like to assign it to multiple, individual variables. This pattern doesn't work: %a is 2x1 of MyClass temp = mat2cell(a); [x,y] = temp{:}; %throws: ??? Insufficient number of outputs from right hand side of equal sign to satisfy assignment. Because temp is a single cell, with my 2x1 array in one cell, rather than a 2x1 cell array with one element of each of my original array in one cell. Any ideas?

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  • Should uni provide "correct answer" after programming assignment is due?

    - by Michael Mao
    Hi all: This is my very first subjective question. And I think it is programming related - the assignment is to be written in a programming language. I am not for "getting the full marks out of a subject". I am actually not for a "correct answer", but for a "better solution", so that I can compare, and can improve. I reckon it is good that I practice programming first and check the solution later to pick up the things I've done wrong/bad. Without a "benchmark" to against, this would be much harder. Unfortunately as far as I know, not all programming subjects taught in uni would kindly provide the students with a "correct answer" in the end, after the assignment is due. One bad metaphor for this is like someone asks you a question which they don't have a clear answer themselves and hope to take advantage of your answer as the basis for their answer. Personally, I feel having a assignment solution provided by the academic staff is essential to students. I do appreciate this, and I feel I might not be the only one. I am a very proactive student in uni. I learn more, I practice more, an assignment for me is more like a challenge to achieve "the best solution I can come up with", not something "I have to pass"... The cause of this question is that for the past few days I have crafted 500+ lines of Perl code, for a tiny assignment. I feel pain when I look at my solution(not finished yet) and I feel like I am an idiot doing some crap code. I know there must be a much better solution. And I reckon it is better for the lecturer in this subject to get me one, rather than asking for an answer here, even I would shamelessly add the link to my solution apart from the assignment requirements. I know in SO, there are a lot of tutors/lecturers for programming subjects/courses. I'd like to hear your words on this question.

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  • How can I evaluate variable to another variable before assigning?

    - by HH
    #!/usr/bin/python # # Description: trying to evaluate array -value to variable before assignment # but it overwrites the variable # # How can I evaluate before assigning on the line 16? #Initialization, dummy code? x=0 y=0 variables = [x, y] data = ['2,3,4', '5,5,6'] # variables[0] should be evaluted to `x` here, i.e. x = data[0], how? variables[0] = data[0] if ( variables[0] != x ): print("It does not work, why?"); else: print("It works!");

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  • Who deletes the copied instance in + operator ? (c++)

    - by Dima
    Hello, I searched how to implement + operator properly all over the internet and all the results i found do the following steps : const MyClass MyClass::operator+(const MyClass &other) const { MyClass result = *this; // Make a copy of myself. Same as MyClass result(*this); result += other; // Use += to add other to the copy. return result; // All done! } I have few questions about this "process" : Isn't that stupid to implement + operator this way, it calls the assignment operator(which copies the class) in the first line and then the copy constructor in the return (which also copies the class , due to the fact that the return is by value, so it destroys the first copy and creates a new one.. which is frankly not really smart ... ) When i write a=b+c, the b+c part creates a new copy of the class, then the 'a=' part copies the copy to himself. who deletes the copy that b+c created ? Is there a better way to implement + operator without coping the class twice, and also without any memory issues ? thanks in advance

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  • C++ OOP - Can you 'overload a cast' <- hard to explain in 1 sentence

    - by Brandon Miller
    Well, the WinAPI has a POINT struct, but I am trying to make an alternative class to this so you can set the values of x and y from a constructor. /** * X-Y coordinates */ class Point { public: int X, Y; Point(void) : X(0), Y(0) {} Point(int x, int y) : X(x), Y(y) {} Point(const POINT& pt) : X(pt.x), Y(pt.y) {} Point& operator= (const POINT& other) { X = other.x; Y = other.y; } }; // I have an assignment operator and copy constructor. Point myPtA(3,7); Point myPtB(8,5); POINT pt; pt.x = 9; pt.y = 2; // I can assign a 'POINT' to a 'Point' myPtA = pt; // But I also want to be able to assign a 'Point' to a 'POINT' pt = myPtB; Is it possible to overload operator= in a way so that I can assign a Point to a POINT? Or maybe some other method to achieve this? Thanks in advance.

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  • Assigning a 2D array (of pointers) to a variable in an object for access in C++?

    - by MrMormon
    I'm sorry if I didn't pick a descriptive or concise name. A lot of questions sound similar, but I haven't been able to find what I'm looking for. What I want to do is store a 2D array of pointers somewhere and assign a variable in some object to that array to be able to access it. Here's some example code that has the same compile error I'm getting with a bigger project. #include <iostream> using namespace std; struct X{ float * b[8][8]; X(){ *(b[1][5]) = 1; cout << *(b[1][5]) << endl; } void Set(float * c[8][8]){ b = c; cout << *(b[1][5]) << endl; } }; main(){ float * a[8][8]; *(a[1][5]) = 2; X obj; obj.Set(a); } What I want to happen in this code is that an X object starts with its own 2D array, whose value pointed to by b[1][5] should be printed as "1". Then the main method's 2D array, a, is passed to the object's Set() method and assigned to its array variable. The value pointed to by b[1][5] should then be printed as "2". However, I can't figure out what type the Set() parameter, c, should be. I get error: incompatible types in assignment of ‘float* (*)[8]’ to ‘float* [8][8]’ when I try to compile. As for why I want to do this, I'm trying to use an array of pointers to objects, not floats, but it's the same error.

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  • how a pure functional programming language manage without assignment statements?

    - by Gnijuohz
    When reading the famous SICP,I found the authors seem rather reluctant to introduce the assignment statement to Scheme in Chapter 3.I read the text and kind of understand why they feel so. As Scheme is the first functional programming language I ever know something about,I am kind of surprised that there are some functional programming languages(not Scheme of course) can do without assignments. Let use the example the book offers,the bank account example.If there is no assignment statement,how can this be done?How to change the balance variable?I ask so because I know there are some so-called pure functional languages out there and according to the Turing complete theory,this must can be done too. I learned C,Java,Python and use assignments a lot in every program I wrote.So it's really an eye-opening experience.I really hope someone can briefly explain how assignments are avoided in those functional programming languages and what profound impact(if any) it has on these languages. The example mentioned above is here: (define (make-withdraw balance) (lambda (amount) (if (>= balance amount) (begin (set! balance (- balance amount)) balance) "Insufficient funds"))) This changed the balance by set!.To me it looks a lot like a class method to change the class member balance. As I said,I am not familiar with functional programming languages,so if I said something wrong about them,feel free to point out.

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  • C++ copy-construct construct-and-assign question

    - by Andy
    Blockquote Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is accomplished through a direct invocation of Y::Y(int). The initializations of b and c are more complex. In fact, they're too complex. These are both copy initializations. In the case of the initialization of b, we're requesting the creation of an anonymous temporary of type Y, initialized with the value 1066. We then use this anonymous temporary as a parameter to the copy constructor for class Y to initialize b. Finally, we call the destructor for the anonymous temporary. To test this, I did a simple class with a data member (program attached at the end) and the results were surprising. It seems that for the case of b, the object was constructed by the copy constructor rather than as suggested in the book. Does anybody know if the language standard has changed or is this simply an optimisation feature of the compiler? I was using Visual Studio 2008. Code sample: #include <iostream> class Widget { std::string name; public: // Constructor Widget(std::string n) { name=n; std::cout << "Constructing Widget " << this->name << std::endl; } // Copy constructor Widget (const Widget& rhs) { std::cout << "Copy constructing Widget from " << rhs.name << std::endl; } // Assignment operator Widget& operator=(const Widget& rhs) { std::cout << "Assigning Widget from " << rhs.name << " to " << this->name << std::endl; return *this; } }; int main(void) { // construct Widget a("a"); // copy construct Widget b(a); // construct and assign Widget c("c"); c = a; // copy construct! Widget d = a; // construct! Widget e = "e"; // construct and assign Widget f = Widget("f"); return 0; } Output: Constructing Widget a Copy constructing Widget from a Constructing Widget c Assigning Widget from a to c Copy constructing Widget from a Constructing Widget e Constructing Widget f Copy constructing Widget from f I was most surprised by the results of constructing d and e.

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  • Group Policy dealing with IE zone assignment not sticking!

    - by Brandon
    I have a group policy (which ONLY deals with the zone assignment) -that is continually switching on and off with reboots. I thought it was a conflicting group policy but when I run group policy modeling report it doesn't show any descrepancies that I can see. I thought it may be an issue with one domain controller wasn't replicating my policy change to the other one, but this isn't the case. I checked both domain controllers and they show the same information. The assignment is on a user basis and is in: user configuration > administrative templates > windows components > internet explorer > internet control panel > security and is site to zone assignment.

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  • In C and C++, what methods can prevent accidental use of the assignment(=) where equivalence(==) is needed?

    - by DeveloperDon
    In C and C++, it is very easy to write the following code with a serious error. char responseChar = getchar(); int confirmExit = 'y' == tolower(responseChar); if (confirmExit = 1) { exit(0); } The error is that the if statement should have been: if (confirmExit == 1) As coded, it will exit every time, because the assignment of the confirmExit variable occurs, then confirmExit is used as the result of the expression. Are there good ways to prevent this kind of error?

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  • Python regular expressions matching variables to end of line

    - by None
    When you use variables (is that the correct word?) in python regular expressions like this: "blah (?P\w+)" ("value" would be the variable), how could you make the variable's value be the text after "blah " to the end of the line or to a certain character not paying any attention to the actual content of the variable. For example, this is pseudo-code for what I want: >>> import re >>> p = re.compile("say (?P<value>continue_until_text_after_assignment_is_recognized) endsay") >>> m = p.match("say Hello hi yo endsay") >>> m.group('value') 'Hello hi yo' Note: The title is probably not understandable. That is because I didn't know how to say it. Sorry if I caused any confusion.

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  • why i add more insignificant code but cost less time

    - by user3714382
    i write a method and when i add some insignificant code it works faster, like these : array[1]=array[1]; array[0]=array[0]; array[3]=array[3]; array[2]=array[2]; i use double t=System.currentTimeMillis(); at first to record the time. then call the method and use System.out.println(System.currentTimeMillis()-t); in the end. when i delete the code (array[1]=array[1];...) the cost time is 1035.0 ms,but if i add these code, the cost time become 898.0ms. here is my method and my code. PS:this method is use for the game 2048, exp: {2,2,2,2} trans to {0,0,4,4} static void toRight2(int[] array){ if (array[2]==array[3] ) { array[3]=array[2]*2; if (array[0]==array[1]) { array[2]=array[1]*2; array[0]=0; array[1]=0; }else { array[2]=array[1]; array[1]=array[0]; array[0]=0; } } else{ if (array[0]==array[1]) { array[1]=array[1]*2; array[0]=0; array[3]=array[3]; array[2]=array[2]; }else { array[1]=array[1];//delete this cost more time array[0]=array[0];//delete this cost more time array[3]=array[3];//delete this cost more time array[2]=array[2];//delete this cost more time } } } public static void main(String[] args) { double t=System.currentTimeMillis(); int[] array={1,2,3,3}; for (int j = 2; j <400*1000000; j++) { toRight2(array); } System.out.println(System.currentTimeMillis()-t); }

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  • how to assign an object to smarty templates?

    - by keisimone
    i created a model object in PHP class User { public $title; public function changeTitle($newTitle){ $this->title = $newTitle; } } How do i expose the property of a User object in smarty just by assigning the object? I know i can do this $smarty->assign('title', $user->title); but my object has something like over 20 plus properties. Please advise. EDIT 1 the following didn't work for me. $smarty->assign('user', $user); OR $smarty->register_object('user', $user); then i try to {$user->title} nothing came out. Thank you.

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  • Sorting tasks to assign

    - by Diego
    I've got a problem that I don't know where to start. I'd realy appreciate some help. The problem: I have several T task that must be done in D days by just 1 employee (let's forget using several resources right now). Each task can be done in some times (not all tasks can be done all time). e.g.: If my employee starts working at 8 o'clock and one task is "call a client". Maybe the client office opens at 9 o'clock. Also each task has a duration (really estimated). It is supposed that the D days are enough to do all task. I've to sort the tasks to the employee. e.g.: at monday 8:00 do task 7, then at 9:30 starts with task 2. In the example task 7 duration would be 1 and a half hour. Thanks for the help! Diego PD: If someone has a way to make this and it is not an algorithm never minds, please answer and I'll manage to think the algorithm. I just don't know how to face the problem. Edit Would Project be usefull? Edit 2 Tasks / Jobs dependency is NOT required

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  • How to create a Turing machine that takes a single digit decimal number from 0 - 9 and output the cu

    - by Julian
    I'm working on a project for a Turning machine but having problems conceptualizing the steps. f(x) = x^3, where x is a single digit between 0 - 9 inclusive. Based on my understanding I am to convert the number to binary but how do I find the cube of a number in binary. Also, how do I write the cube on the tape. So far I'm thinking I should create a state diagram that accepts the binary versions of 0-9 but what next?

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  • DFS function, can you guys tell me what is the wrong with this code?

    - by danielDhobbs
    can you guys tell me what is the wrong with this code? it is not working with 1 2 1 3 1 4 2 5 2 6 2 7 2 8 3 8 3 9 4 10 1 - 4 - 10 and stop DFS function void Is_Connected(graphType* g, int v){ //function to define the graph is connected or not int i=0; g_node* w; top = NULL; g -> visited[v] = TRUE; push(v); printf("%d", v); while (top != NULL) { w = g -> adjList[v]; while (w) { if (!g -> visited[w -> vertex]) { push(w -> vertex); g -> visited[w -> vertex] = TRUE; printf("->%d", w->vertex); v = w -> vertex; w = g -> adjList[v]; } else { w = w -> link; } } i++; v = pop(); } if (i == (g -> x)-1){ //number of vertices = number of vertetices pass through puts("\nIs_Connected() result : yes"); } else{ puts("\nIs_Connected() result : no"); } }

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  • plt-scheme : catching mouse click event on canvas

    - by Thura
    I am writing a tic-tac-toe game in plt-scheme as my AI course project. The idea for gui is a grid with 9 boxes, each with a canvas, using panes ... When the user click on a canvas, 'X' or 'O' will be drawn accordingly ... The question is how can I catch mouse click event on canvas? I found out I need to use on-event, but still don't know how? Any clues?

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  • std::map operator[] and automatically created new objects

    - by thomas-gies
    I'm a little bit scared about something like this: std::map<DWORD, DWORD> tmap; tmap[0]+=1; tmap[0]+=1; tmap[0]+=1; Since DWORD's are not automatically initialized, I'm always afraid of tmap[0] being a random number that is incremented. How does the map know hot to initialize a DWORD if the runtime does not know how to do it? Is it guaranteed, that the result is always tmap[0] == 3?

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