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  • += Overloading in C++ problem.

    - by user69514
    I am trying to overload the += operator for my rational number class, but I don't believe that it's working because I always end up with the same result: RationalNumber RationalNumber::operator+=(const RationalNumber &rhs){ int den = denominator * rhs.denominator; int a = numerator * rhs.denominator; int b = rhs.numerator * denominator; int num = a+b; RationalNumber ratNum(num, den); return ratNum; } Inside main //create two rational numbers RationalNumber a(1, 3); a.print(); RationalNumber b(6, 7); b.print(); //test += operator a+=(b); a.print(); After calling a+=(b), a is still 1/3, it should be 25/21. Any ideas what I am doing wrong?

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  • Is return an operator or a function?

    - by eSKay
    This is too basic I think, but how do both of these work? return true; // 1 and return (true); // 2 Similar: sizeof, exit My guess: If return was a function, 1 would be erroneous. So, return should be a unary operator that can also take in brackets... pretty much like unary minus: -5 and -(5), both are okay. Is that what it is - a unary operator?

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  • Problem with variable argument function in C++

    - by Freezerburn
    I'm trying to create a variable length function (obviously, heh) in C++, and what I have right now works, but only for the first argument. If someone could please let me know how to get this working with all the arguments that are passed, I would really appreciate it. Code: void udStaticObject::accept( udObjectVisitor *visitor, ... ) { va_list marker; udObjectVisitor *i = visitor; va_start( marker, visitor ); while( 1 ) { i->visit_staticObject( this ); //the if here will always go to the break immediately, allowing only //one argument to be used if( ( i = va_arg( marker, udObjectVisitor* ) ) ) break; } va_end( marker ); } Based on my past posts, and any help posts I make in general, there is probably some information that I did not provide that you will need to know to help. I apologize in advance if I forgot anything, and please let me know what you need to know so I can provide the information.

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  • Behavior of virtual function in C++

    - by Summer_More_More_Tea
    Hi everyone: I have a question, here are two class below: class Base{ public: virtual void toString(); // generic implementation } class Derive : public Base{ public: ( virtual ) void toString(); // specific implementation } The question is: If I wanna subclass of class Derive perform polymophism using a pointer of type Base, is keyword virtual in the bracket necessary? If the answer is no, what's the difference between member function toString of class Derive with and without virtual?

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  • How can I take any function as input for my Scala wrapper method?

    - by pr1001
    Let's say I want to make a little wrapper along the lines of: def wrapper(f: (Any) => Any): Any = { println("Executing now") val res = f println("Execution finished") res } wrapper { println("2") } Does this make sense? My wrapper method is obviously wrong, but I think the spirit of what I want to do is possible. Am I right in thinking so? If so, what's the solution? Thanks!

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  • Does "Value Restriction" practically mean that there is no higher order functional programming?

    - by Sadache
    Does "Value Restriction" practically mean that there is no higher order functional programming? I have a problem that each time I try to do a bit of HOP I get caught by a VR error. Example: let simple (s:string)= fun rq->1 let oops= simple "" type 'a SimpleType= F of (int ->'a-> 'a) let get a = F(fun req -> id) let oops2= get "" and I would like to know whether it is a problem of a prticular implementation of VR or it is a general problem that has no solution in a mutable type-infered language that doesn't include mutation in the type system.

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  • Assigning function within function object without invoking the function itself.

    - by webzide
    Dear experts, I am trying to assign an function within an function object property without actually invoking then function itself. for instance, I have the following function object class definition function objectOne(name, value, id){ this.name=name; this.value=value; this.id=id; this.methodOne=methodFunction(this); } the last line this.methodOne=methodFunction(this); I want to pass the current object to the function but at the same time i don't want to execute the function right now. But if I do it this way without the bracket this.methodOne=methodFunction then the argument of this object would not be passed as a parameter to the function. Is there a way to work through this. Thank you in advance

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  • How do you return a string from a function correctly in Dynamic C?

    - by aquanar
    I have a program I am trying to debug, but Dynamic C apparently treats strings differently than normal C does (well, character arrays, anyway). I have a function that I made to make an 8 character long (well, 10 to include the \0 ) string of 0s and 1s to show me the contents of an 8-bit char variable. (IE, I give it the number 13, it returns the string "0001101\0" ) When I use the code below, it prints out !{happy face] 6 times (well, the second one is the happy face alone for some reason), each return comes back as 0xDEAE or "!\x02. I thought it would dereference it and return the appropriate string, but it appears to just be sending the pointer and attempting to parse it. This may seem silly, but my experience was actually in C++ and Java, so going back to C brings up a few issues that were dealt with in later programming languages that I'm not entirely sure how to deal with (like the lack of string variables). How could I fix this code, or how would be a better way to do what I am trying to do (I thought maybe sending in a pointer to a character array and working on it from the function might work, but I thought I should ask to see if maybe I'm just trying to reinvent the wheel). Currently I have it set up like this: this is an excerpt from the main() display[0] = '\0'; for(i=0;i<6;i++) { sprintf(s, "%s ", *char_to_bits(buffer[i])); strcat(display, s); } DispStr(8,5, display); and this is the offending function: char *char_to_bits(char x) { char bits[16]; strcpy(bits,"00000000\0"); if (x & 0x01) bits[7]='1'; if (x & 0x02) bits[6]='1'; if (x & 0x04) bits[5]='1'; if (x & 0x08) bits[4]='1'; if (x & 0x10) bits[3]='1'; if (x & 0x20) bits[2]='1'; if (x & 0x40) bits[1]='1'; if (x & 0x80) bits[0]='1'; return bits; } and just for the sake of completion, the other function is used to output to the stdio window at a specific location: void DispStr(int x, int y, char *s) { x += 0x20; y += 0x20; printf ("\x1B=%c%c%s", x, y, s); }

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  • C ++ virtual function

    - by user2950788
    masters of C++. I am trying to implement polymorphism in C++. I want to write a base class with a virtual function and then redefine that function in the child class. then demonstrate dynamic binding in my driver program. But I just couldn't get it to work. I know how to do it in C#, so I figured that I might have made some syntactical mistakes where I had used C#'s syntax in my C++ code, but these mistakes are not obvious to me at all. So I'd greatly appreciate it if you would correct my mistakes. class polyTest { public: polyTest(); virtual void type(); virtual ~polyTest(); }; void polyTest::type() { cout << "first gen"; } class polyChild: public polyTest { public: void type(); }; void polyChild::type() { cout << "second gen"; } int main() { polyChild * ptr1; polyChild * ptr2; ptr1 = new polyTest(); ptr2 = new polyChild(); ptr1 -> type(); ptr2 -> type(); }

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  • Javascript function programming — receiving elaborate parameters

    - by Barney
    I'm writing a Javascript function that would manipulate an array written on-the-fly and sent as a parameter. The function is written as follows: function returnJourney(animation,clean){ var properties = {}; // loads of other inane stuff for(i in animation[0]) properties[animation[0][i]] = animation[0].i; // heaps more inane stuff } The animation in question is a set of parameters for a jQuery animation. Typically it takes the format of ({key:value,key:value},speedAsInteger,modifierAsString). So to kick off initial debugging I call it with: returnJouney(({'foo':'bar'},3000),1); And straight off the bat things are way off. As far as I see it this would have returnJourney acknowledge clean === 1, and animation being an array with an object as its first child and the number 3000 as its second. Firebug tells me animation evaluates as the number 3000. What am I doing wrong?

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  • c++ Array passing dilemma

    - by Thomas
    Hi, I am writing a function that takes a string, string pointer and an int. The function splits the string based on a set of rules and puts each token into an array. I need to return the array out of the function with the number of elements in the int variable etc. I am stuck as to how I return the array as I can not use auto other wise it is destroyed and I am reluctant to use new as I feel this is patchy. I have other ideas on how to go about this but would like to see how other people go about this first. I could also be wrong and it could be possible to pass an auto out of an array. I can also not use vectors so there goes a copy constructor.

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • include() Why should I not use it?

    - by aliov
    I am working through an older php mysql book written in 2003. The author uses the include() function to construct html pages by including header.inc, footer.inc, main.inc files, etc. Now I find out that this is not allowed in the default ini settings, (allow_url_include is set to Off) after I got many warnings from the server. I noticed also that you can use include without the parenthesis. I tried this and it works and I get no error messages or warnings. Are the two different? That is, is include() different from include ?

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  • What are parts of a PHP function named?

    - by MikeG
    I am having trouble figuring out a problem and it is because I don't know the correct terms to be searching for. Could someone please name all the parts of a PHP function and if I'm missing something please add it. function my_function( non_variable $variable_one, $variable_two = "", $variable_three ) { /* inside stuff (Statement?) */ } The answer I'm looking for would look something like this function: declaration my_function: name non_variable: Please Answer $variable_one: variable filled with non_variable The one I really need to know about are non_variable and $variable_one, Thanks! EDIT: more detail about the function function my_function(custom_name $company) { $website = $company->company_website; /* Additional stuff */ }

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  • Toggle Image Overlays in Google Maps API v3

    - by Douglas
    Hey guys. I've been building a small library for myself for a job I have at the moment building a map for a university. I've gotten pretty well everything I need in some basic form, but one thing has simply not been working, and is simply not giving me results. The university itself is sort of in a partnership with the neighboring college. It's been decided that both campuses should be included. I need to be able to toggle on/off the overlays of the campuses individually. i.e. Start with all campuses ON. User then turns OFF college campus, university overlay stays up. User can then turn it back on to display the college once more, or turn off the university as well, leaving no overlays. Here's a work in progress I'm doing at the moment: http://bgsweb.ca/maps/generator.html Basically, we need to take the one overlay, split it into multiple overlays, and enable the toggling of each individual overlay. Any assistance much appreciated!

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  • Is it possible to have a variadic function in C with no non-variadic parameter?

    - by Tim
    I have the following function: void doStuff(int unusedParameter, ...) { va_list params; va_start(params, unusedParameter); /* ... */ va_end(params); } As part of a refactor, I'd like to remove the unused parameter without otherwise changing the implementation of the function. As far as I can tell, it's impossible to use va_start when you don't have a last non-variadic parameter to refer to. Is there any way around this? Background: It is in fact a C++ program, so I could use some operator-overloading magic as suggested here, but I was hoping not to have to change the interface at this point. The existing function does its work by requiring that the variable argument list be null-terminated, and scanning for the NULL, therefore it doesn't need a leading argument to tell it how many arguments it has.

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  • Making a function for selecting from MySQL, how is mine?

    - by Doug
    This is my first time. I will appreciate any thoughts, tips, and what not. How can I improve this? Ultimately, I don't want so many selects in my script. function mysqlSelectCodes($table, $where, $order, $limit) { $sql = "SELECT * FROM $table WHERE $where ORDER BY $order LIMIT $limit" or die(mysql_error()); }

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  • Dynamic creation of a pointer function in c++

    - by Liberalkid
    I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?

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  • PHP Array Not Working in Function

    - by lemonpole
    Hello all. I'm currently experimenting with arrays in PHP, and I created a fake environment where a team's information will be displayed. $t1 = array ( "basicInfo" => array ( "The Sineps", "December 25, 2010", "lemonpole" ), "overallRecord" => array (0, 0, 0, 0), "overallSeasons" => array ( 1 => array (14, 0, 0), 2 => array (9, 5, 2), 3 => array (12, 4, 0), 4 => array (3, 11, 2) ), "games" => array ( "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />", "<img src=\"images/cs.gif\" alt=\"Counter-Strike\" />" ), "seasonHistory" => array ( "Season I", "Season II", "Season III", "Season IV" ), "divisions" => array ( "Open", "Main", "Main", "Invite" ) ); // Displays the seasons the team has been in along // with the record of each season. function seasonHistory() { // Make array variable local-scope. global $t1; // Count the number of seasons. $numrows = count($t1["seasonHistory"]); // Loop through all the variables until // it reaches the last entry made and display // each item seperately. for($v = 0; $v <= $numrows; $v++) { // Echo each season. echo "<tr><td>{$t1["games"][$v]}</td>"; echo "<td>{$t1["seasonHistory"][$v]}</td>"; echo "<td>{$t1["divisions"][$v]}</td></tr>"; } } I have tested several possible problems out and after narrowing them down I have come down to one conclusion and that is my function is not connecting to the array for some reason. I don't know what else to do because I thought making the array global would fix that problem. What works: I can echo $t1["games"][0] on the page I need it to display and it gives me the content. I tried echo $t1["games"][0] INSIDE the function and then calling the function and it doesn't display anything.

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  • How with lambda function in MVC3

    - by doogdeb
    I have a model which contains view models for each view. This model is held in session and is initialised when application starts. I need to be able to populate a field from one view model with the value from another so have used a lambda function. Below is my model. I am using a lambda so that when I get Test2.MyProperty it will use the FunctionTestProperty to retrieve the value from Test1.TestProperty. public class Model { public Model() { Test1 = new Test1() Test2 = new Test2(FunctionTestProperty () => Test1.TestProperty) } } public class Test1 { public string TestProperty { get; set; } } public class Test2 { public Test2() : this (() => string.Empty) {} public Test2(Func<string> functionTestProperty) { FunctionTestProperty = functionTestProperty; } public Func<string> FunctionTestProperty { get; set; } public string MyProperty { get{ return FunctionTestProperty() ?? string.Empty; } } } This works perfectly when I first run the application and navigate from Test1 to Test2; I can see that when I get the value for MyProperty it calls back to Model constructor and retrieves the Test1.TestProperty value. However when I then submit the form (Test2) it calls the default constructor which sets it to string.Empty. So if I go back to Test1 and back to Test2 again it always then calls the Test2 default constructor. Does anyone know why this works when first running the application but not after the view is submitted, or if I have made an obvious mistake?

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