struct

问题 I have the following struct: typedef struct _chess { int **array; int size; struct _chess *parent; } chess; and I have: typedef struct _chess *Chess; Now, I want to create an array of dynamic length to store pointers to the chess struct so I do the following: Chess array [] = malloc(size * sizeof(Chess)); This gives me an error: invalid initializer. And if I drop the [] and do this: Chess array = malloc(size * sizeof(Chess)); it compiles without error but when I try to set an element of this

问题 I'm doing a raytracer hobby project, and originally I was using structs for my Vector and Ray objects, and I thought a raytracer was the perfect situation to use them: you create millions of them, they don't live longer than a single method, they're lightweight. However, by simply changing 'struct' to 'class' on Vector and Ray, I got a very significant performance gain. What gives? They're both small (3 floats for Vector, 2 Vectors for a Ray), don't get copied around excessively. I do pass

问题 The C# compiler is a bit ... old fashioned ... and won't do static analysis. So it breaks on seemingly correct code like this: MyStruct s; bool inited = false; foreach( Something foo in ACollection ) { if( foo.Test() ) continue; if( inited ) s.DoSomething(); else { s = foo.GetMeAnS(); inited = true; } } Note: the unusual problem is that "s" is a struct. If it were a class, I'd simply init it to null. This struct has no meaningful "uninited" state, and I don't want to pay the performance cost

问题 There are 2 kinds of variables that I have. Check for the Go playground, and I don't understand why this is happening. The problem: what I get from the Models it should be a struct to use it for GORM First() function. The code: package main import ( "fmt" ) type Test struct { Test string } var Models = map[string]interface{}{ "test": newTest(), } func main() { test1 := Test{} fmt.Println("Test 1: ") fmt.Printf("%v", test1) fmt.Println() fmt.Println("Test 1 as pointer: ") fmt.Printf("%v",

问题 on Swift String is a struct and you could just initialize it using var someString:String = "Hello" how would I make another Struct initializable like String? for example struct StringV2 { init() } class SomeClass { let someStringV2:StringV2 = "Hello" } Since that's how String 's code looks like. 回答1: This is (in my opinion) neat part of the language. Yes, this is possible, thanks to the ExpressibleByStringLiteral protocol. Unfortunately, there is some complexity to it.

问题 This question already has answers here : How can you make a safe static singleton in Rust? (2 answers) How do I create a global, mutable singleton? (1 answer) Closed last year . How do I declare an instance of one of my own structs as static? This sample doesn't compile: static SERVER: Server<'static> = Server::new(); fn main() { SERVER.start("127.0.0.1", 23); } 回答1: You can’t call any non- const functions inside a global. Often you will be able to do something like struct literals, though

问题 This question already has answers here : What are some efficient ways to combine two structures in MATLAB? (5 answers) Closed 5 years ago . I'm wondering if there is a convenient way to update a struct with the values of another struct in Matlab. Here is the code, with the use of fieldnames , numel and a for loop, fn = fieldnames(new_values); for fi=1:numel(fn) old_struct.(fn{fi}) = new_values.(fn{fi}); end Of course, I don't want to loose the fields in old_struct that are not in new_values ,

问题 This question already has answers here : What are some efficient ways to combine two structures in MATLAB? (5 answers) Closed 5 years ago . I'm wondering if there is a convenient way to update a struct with the values of another struct in Matlab. Here is the code, with the use of fieldnames , numel and a for loop, fn = fieldnames(new_values); for fi=1:numel(fn) old_struct.(fn{fi}) = new_values.(fn{fi}); end Of course, I don't want to loose the fields in old_struct that are not in new_values ,

问题 I'm trying to figure out how exactly to use stat() to capture information about a file. What I need is to be able to print several fields of information about a file. So.. #include <iostream> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> using namespace std; int main() { struct stat buf; stat("file",&buf); ... cout << st_dev << endl; cout << st_ino << endl; cout << st_mode << endl; cout << st_nlink << endl; cout << st_uid << endl; cout << st_gid << endl; cout << st_rdev <<

问题 How does a function return value is clear to me, just to kick start: int f() { int a = 2; return a; } Now a gets the memory in stack and its life-span is within the f() in order to return the value it copies the value to a special register which is read by the caller as it knows that the callee have placed the value for him. (Since the size of return-value-holder special register size is limited that's why we cant return large objects therefore In case of advance languages when we want to