void

问题 I have this simple "interface" for some plugins I want to develop, it looks like: class TestPluginBase : public QObject { Q_OBJECT public: TestPluginBase(); qint64 returnType(){return PluginType;} protected: qint64 PluginType; }; And some other classes which implement the "interface" like: class TestPluginONE : public TestPluginBase { public: TestPluginONE() {this->PluginType =1;} qint64 returnType() {return this->PluginType;} }; Then I have another function which suppose to load different

问题 Consider the following code: template<typename F> struct S; template<typename Ret, typename... Args> struct S<Ret(Args...)> { }; template<typename... Args> using Alias = S<void(Args...)>; int main() { S<void(int)> s; Alias<int> alias; } It works fine, as expected and both the line involving S and the one involving Alias define under the hood the same type S<void(int)> . Now, consider the following changes: int main() { S<void(void)> s; // this line compiles Alias<void> alias; // this line

问题 For a list of reasons that I do not control, I need to create an array of strings that needs to be referenced from a void* pointer. The idea is to follow the following pattern in C++: void* TP = malloc(sizeof (double) * SS); for (int i = 0; i < SS; i++) { ((double*) TP)[i] = IStringToDouble(Token[i]); } Where Token is a vector and SS an int. Now, using that template, I though starting with something like: void* TP = malloc(sizeof (string) * SS); for (int i = 0; i < SS; i++) { ((string*) TP)[i

问题 i wrote this double linked list with void pointers typedef struct list_el { void *data; struct list_el *prev; struct list_el *next; } list_el; typedef struct linked_list { int n_el; /*number of elements*/ list_el * head; /*pointer to the head*/ list_el * tail; /*pointer to the head*/ } linked_list; and i wrote those functions to handle with it. /*for list_el allocation*/ list_el * new_el ( void ) { return (list_el *) malloc(sizeof(list_el)); } /*list initialization*/ void init_list(linked

问题 Void variable has nothing to do and also void pointer can only be pointed with casting. So void pointer is used when we actually don't know where and of which data type we want to point. But what is of void variable? Any practical example? 回答1: In C void can't be considered a data type, it is a keyword used as a placeholder in place of a data type to show that actually there is no data. For example consider the function void f(void); . Here the keyword void is used to mean the absence of any

问题 This question already has answers here : How do you pass a function as a parameter in C? (7 answers) Closed last year . I get this error when trying to compile: `error: invalid use of void expression I get this error at the penultimate line: queueDump(f, q, printToken(f, e)); and I don't understand why. I'm trying to code the function printToken that prints the token pointed by e void queueDump(FILE *f, Queue *q, void(*dumpfunction)(FILE *f, void *e)) { fprintf(f, "(%d) -- ", q->size); for

问题 I need to set the temperature class, and need to alter the degrees in a void method. How do I access these variables in a void method, and ensure that the void method alters the parameters into the variables that I need? I need the degrees to be converted, and I don't know how to access the degree variable not in the set class? Temperature (double enteredtemp,char scale ){ degrees=Temperature.set(); } public void set (double enteredtemp, char scale){ if (scale=='r'||scale=='R'){ degrees=

问题 Previously, I'd just dealt with these types of __out function parameters using malloc, but I'm trying to change my ways. As a specific example, in a class to manage Raw Input, GetRawInputDeviceInfo() is prototyped as such: UINT GetRawInputDeviceInfo(HANDLE, UINT, LPVOID, PUINT) LPVOID is a pointer to a buffer containing the information I need. PUINT is a pointer to a UINT containing the size of data contained in the buffer pointed to by LPVOID. Normally, I would (once I have populated the

问题 I tried running the following scheme code: (define affiche-gagnant (lambda (j1 j2 g1 g2) (begin (display "Le gagnant est : ") (display (cond ((> g1 g2) j1) ((< g1 g2) j2) (else (begin (display "personne. ") (display j1) (display " et ") (display j2) (display " sont exaequos. ")))))))) But I get the following output: Le gagnant est : personne. Alper et Ezgi sont exaequos. #<void> Where did the #void come from? How do I get rid of it? 回答1: Oops, wrong answer. You have an extra display: (define

问题 I need to void a payment made in netsuite by using NetSuite webservice. Is it possible? I have tried by adding Journal entry for the payment which i need to void. But it doesn't work for me. Any help on this is appreciated. 回答1: If you're using suite scripts you can use nlapiVoidTransaction(transactionType, recordId); This API is supported in the following script types: Client User Event Scheduled Suitelet RESTlet Workflow Action The Governance on this API is 10. 回答2: The general rule in