struct

问题 I am trying to move some functions to separate file in c project. I made util.h file with #ifndef _UTIL_H #define _UTIL_H #include <signal.h> #include <termios.h> #include <time.h> ... extern struct timeval tv1, tv2, dtv; void time_start(); long time_stop(); and I made util.c file with #include "util.h" ... struct timeval tv1, tv2, dtv; void time_start() { gettimeofday(&tv1, &timezone); } long time_stop() { gettimeofday(&tv2, &timezone); dtv.tv_sec = tv2.tv_sec - tv1.tv_sec; ... in cmake I

问题 When you define a struct globally, why can't you define the structure members globally as well (outside of using the initializer syntax)? The error I'm getting from clang is that system_1 has an "unknown type name". If you define the struct within a function, such as main() , then you don't run into any issues. typedef struct Light_System { int redLightPin; int yellowLightPin; int blueLightPin; } Light_System; Light_System system_1; # "Light_System system_1 = {4, 0, 0}" works system_1

问题 I want to create a function (for a library) which will output a struct for any CSV which contains all the columns and their data. This means that the column names (unless explicitly provided by the user) will not be known until runtime. Is it possible to create a struct definition at runtime or mutate an existing struct? If so, how? For example, how can I mutate the following struct structure: struct Point { x: String, y: String, } To the following (in memory only): struct Point { x: String,

问题 I have a very basic struct that has an enum and a union. typedef struct { enum v{a,b,c}v; union w{ int a; bool b; std::string c; }w; }Data_Set2; int main() { Data_Set2 val; // Shows errror that the default constructor cannot be referenced return 0; } On using such a struct I get the Error Code C2280 that the default constructor cannot be referenced. When I declare the struct in a slightly different way as following typedef struct { enum v{a,b,c}v; union w{ int a; bool b; std::string c; }; //

问题 class CRectangle { int x, y; public: void set_values (int,int); int area (void); } rect; In this example, what does 'rect' after the closing brace and between the semi-colon mean in this class definition? I'm having trouble finding a clear explanation. Also: Whatever it is, can you do it for structs too? 回答1: rect is the name of a variable (an object in this case). It is exactly as if it had said: int rect; except instead of int there is a definition of a new type, called a CRectangle .

问题 I understand that Swift's tuples serve, for example, as a simple way for a function to return multiple values. However, beyond this "simplicity aspect", I don't see very well any necessity of using tuples instead of structs. Therefore, my question: in terms of design, is there any scenario where tuples are clearly a better choice than structs? 回答1: This question of a slightly "discussion" nature, but I'll add two points in favour of sometimes preferring tuples over structures. Native

问题 I am working on a Coupon form in which I have some optional fields. Introduction: All the form field values are received as JSON and mapped into a Golang structure. In the structure, I have added an "omitempty" flag with every field. So only those form values are mapped which have some appropriate value, rest of the values like 0, " ", false are ignored by the structure. Here is the Golang structure type Coupon struct { Id int `json:"id,omitempty" bson:"_id,omitempty"` Name string `json:"name

问题 I don't know why the below happens, and I can't find source code relative. Can anybody explain to me? var s, ss struct{} // two empty structs arr1 := [6]*struct{}{&s} // array with empty struct pointer arr2 := [6]*struct{}{&ss} // array with empty struct pointer fmt.Println(&s == &ss, arr1 == arr2) // false, true var l, ll struct{A int}{} arr3 := [6]*struct{A int}{&l} // array with empty struct pointer arr4 := [6]*struct{A int}{&ll} // array with empty struct pointer fmt.Println(&l == &ll,

问题 I don't know why the below happens, and I can't find source code relative. Can anybody explain to me? var s, ss struct{} // two empty structs arr1 := [6]*struct{}{&s} // array with empty struct pointer arr2 := [6]*struct{}{&ss} // array with empty struct pointer fmt.Println(&s == &ss, arr1 == arr2) // false, true var l, ll struct{A int}{} arr3 := [6]*struct{A int}{&l} // array with empty struct pointer arr4 := [6]*struct{A int}{&ll} // array with empty struct pointer fmt.Println(&l == &ll,

问题 I don't know why the below happens, and I can't find source code relative. Can anybody explain to me? var s, ss struct{} // two empty structs arr1 := [6]*struct{}{&s} // array with empty struct pointer arr2 := [6]*struct{}{&ss} // array with empty struct pointer fmt.Println(&s == &ss, arr1 == arr2) // false, true var l, ll struct{A int}{} arr3 := [6]*struct{A int}{&l} // array with empty struct pointer arr4 := [6]*struct{A int}{&ll} // array with empty struct pointer fmt.Println(&l == &ll,