struct

问题 I'm creating a simple matrix struct in Rust and I'm trying to implement some basic operator methods: use std::ops::Mul; struct Matrix { cols: i32, rows: i32, data: Vec<f32>, } impl Matrix { fn new(cols: i32, rows: i32, data: Vec<f32>) -> Matrix { Matrix { cols: cols, rows: rows, data: data, } } } impl Mul<f32> for Matrix { type Output = Matrix; fn mul(&self, m: f32) -> Matrix { let mut new_data = Vec::with_capacity(self.cols * self.rows); for i in 0..self.cols * self.rows { new_data[i] = self

问题 Is there any effective difference between these two styles of allocating memory? 1. typedef struct { uint8_t *buffer; } Container; Container* init() { Container* container = calloc(sizeof(Container), 1); container->buffer = calloc(4, 1); return container; } 2. typedef struct { uint8_t buffer[4]; } Container; Container* init() { Container* container = calloc(sizeof(Container), 1); return container; } As far as I understand, the whole Container struct will be heap allocated and buffer will

问题 Couple of issues with python struct. Please let me know what is correct. Document mentions length of l/L as 4 but when checked with calcsize it gives 8. >>> struct.calcsize('l') 8 struct module calcsize is giving wrong size. If individual element size is calculated, it's sum is 90 but when calculated together with calcsize it gives 92. >>> struct.calcsize('8s2sIII30s32s6s') 92 >>> struct.calcsize('8s') 8 >>> struct.calcsize('2s') 2 >>> struct.calcsize('III') 12 >>> struct.calcsize('30s') 30 >

问题 I know that in C, the first member of a struct is guaranteed to have no padding before it. Thus &mystruct == &mystruct.firstmember is always true. This allows the "struct inheritance" technique, as described in this question: typedef struct { // base members } Base; typedef struct { Base base; // derived members } Derived; // ... later Base* object = (Base*) malloc(sizeof()); // This is legal However, I'd like to make sure that this actually works safely with unlimited layers of "inheritance"

问题 Let's say I define a struct in C. If I declare an instance of that struct, it's necessary that I include the 'struct' keyword in front of it. // Define struct struct Book { char title[50]; char author[50]; char subject[100]; int book_id; }; // Instantiate struct int main() { struct Book myBook; } My question: why is it necessary for the struct keyword to precede any instantiation of the struct? It seems like the compiler would have plenty of information to deduct that 'Book' is a struct. I

问题 Let's say I define a struct in C. If I declare an instance of that struct, it's necessary that I include the 'struct' keyword in front of it. // Define struct struct Book { char title[50]; char author[50]; char subject[100]; int book_id; }; // Instantiate struct int main() { struct Book myBook; } My question: why is it necessary for the struct keyword to precede any instantiation of the struct? It seems like the compiler would have plenty of information to deduct that 'Book' is a struct. I

问题 Analyzing some part of software written by someone else, I found the following line of code: typedef const struct rpc_method *(*super_t)(RPC*); Ok, i know, typedef rpc_method *(*super_t)(RPC*); declares a type super_t which is a function pointer... I also know what typedef struct means, but the combination of the two?? Is it a struct with a single entry??? And what means const in this context?? Could it be that const and struct are exchanged??? Nevertheless seems to compile with my gcc eabi.

问题 Analyzing some part of software written by someone else, I found the following line of code: typedef const struct rpc_method *(*super_t)(RPC*); Ok, i know, typedef rpc_method *(*super_t)(RPC*); declares a type super_t which is a function pointer... I also know what typedef struct means, but the combination of the two?? Is it a struct with a single entry??? And what means const in this context?? Could it be that const and struct are exchanged??? Nevertheless seems to compile with my gcc eabi.

问题 Analyzing some part of software written by someone else, I found the following line of code: typedef const struct rpc_method *(*super_t)(RPC*); Ok, i know, typedef rpc_method *(*super_t)(RPC*); declares a type super_t which is a function pointer... I also know what typedef struct means, but the combination of the two?? Is it a struct with a single entry??? And what means const in this context?? Could it be that const and struct are exchanged??? Nevertheless seems to compile with my gcc eabi.

问题 I’m using SwfitUI in my project and I have a NavigationView and List. I’m clicking cell after open the detail view and click navigation back button. I want to remove view (it’s struct, in SwiftUI) after click navigation back button. Because if I click the same cell or button again, it isn’t initialize new view, it’s shows old view. I want to do refresh this view. How do I do? My FirstView Struct is: struct FirstView: View { @ObservedObject var viewModel: FirstViewModel var body: some View {