struct

问题 I am attempting to understand; and resolve, why the following happens: $ python >>> import struct >>> list(struct.pack('hh', *(50,50))) ['2', '\x00', '2', '\x00'] >>> exit() $ python3 >>> import struct >>> list(struct.pack('hh', *(50, 50))) [50, 0, 50, 0] I understand that hh stands for 2 shorts. I understand that struct.pack is converting the two integers (shorts) to a c style struct . But why does the output in 2.7 differ so much from 3.5? Unfortunately I am stuck with python 2.7 for right

问题 I am attempting to understand; and resolve, why the following happens: $ python >>> import struct >>> list(struct.pack('hh', *(50,50))) ['2', '\x00', '2', '\x00'] >>> exit() $ python3 >>> import struct >>> list(struct.pack('hh', *(50, 50))) [50, 0, 50, 0] I understand that hh stands for 2 shorts. I understand that struct.pack is converting the two integers (shorts) to a c style struct . But why does the output in 2.7 differ so much from 3.5? Unfortunately I am stuck with python 2.7 for right

问题 After doing a ton of testing and writing this answer (note: the downvote on it was BEFORE my total rewrite of it), I can't understand why = {0} doesn't set all members of the struct to zero! If you do this: struct data_t { int num1 = 100; int num2 = -100; int num3; int num4 = 150; }; data_t d3 = {0}; printf("d3.num1 = %i\nd3.num2 = %i\nd3.num3 = %i\nd3.num4 = %i\n\n", d3.num1, d3.num2, d3.num3, d3.num4); ...the output is: d3.num1 = 0 d3.num2 = -100 d3.num3 = 0 d3.num4 = 150 ...although I

问题 The MSDN clearly states For all other types, including structs, the sizeof operator can only be used in unsafe code blocks. The C# Language Specification is even more precise : The order in which members are packed into a struct is unspecified. For alignment purposes, there may be unnamed padding at the beginning of a struct, within a struct, and at the end of the struct. The contents of the bits used as padding are indeterminate. When applied to an operand that has struct type, the result is

问题 Here is a related C answer that doesn't work (as a zero initializer for a struct) on C++: Initializing a struct to 0. One of the solutions presented is this: myStruct _m1 = {0}; This works fine in C, but it doesn't work in C++. :( : error: cannot initialize a member subobject of type 'myScope::MyStruct' with an rvalue of type 'int'`. How do you zero-initialize a struct in C++? Related: Initializing a struct to 0 in C: Initializing a struct to 0 Update: (an adjacent, but NOT duplicate question

问题 I've seen two pieces of Go code using this pattern: type SomeType struct{ Field1 string Field2 bool _ struct{} // <-- what is this? } Can anyone explain what this code accomplishes? 回答1: This technique enforces keyed fields when declaring a struct. For example, the struct: type SomeType struct { Field1 string Field2 bool _ struct{} } can only be declared with keyed fields: // ALLOWED: bar := SomeType{Field1: "hello", Field2: "true"} // COMPILE ERROR: foo := SomeType{"hello", true} One reason

问题 I implemented an interface Fruit and two implementations of it: Apple and Banana . Into objects of the two implementations I want to load data from a yaml file: capacity: 4 Apple: - name: "apple1" number: 1 - name: "apple2" number: 1 Banana: - name: "banana1" number: 2 I implemented the UnmarshalYaml interface to load data into my objects: package main import ( "errors" "gopkg.in/yaml.v3" "log" "fmt" ) type FruitBasket struct { Capacity int `yaml:"capacity"` Fruits []Fruit } func

问题 I have this struct below struct foo { char *name; int (*validate)(u8_t *data, size_t size); u8_t value; u8_t changed; foo_id id; }; typedef struct foo foo_t; I wish I to create an array of foo_t in compiling time through defines, like this: int my_validate(u8_t *data, size_t size) {...} FOO_CREATE(my_name, my_validate, 0, 0); FOO_CREATE(my_name2, NULL, 0, 0); and in compiling time the result be: enum { MY_NAME_FOO = 0, MY_NAME2_FOO, FOO_COUNT } foo_id; static foo_t foo[FOO_COUNT] = { { .name

问题 I want to know the actual use of struct tag_name in C programming. Without using the tag_name also i was getting output as with use of tag_name. I want the exact reason behind this process. For ex: //With tag_name st1 struct st1 { int x; char c;}x={100,'a'},y={70,'e'}; //Without any tag_name struct { int x; char c;}x={100,'a'},y={70,'e'}; printf("x.x= %d \t x.c= %c \n",x.x,x.c); //Output: x.x=100 x.c=a printf("y.x= %d \t y.c= %c \n",y.x,y.c); //Output: y.x=70 y.c=e 回答1: In the first case :

问题 This question already has answers here : How do I do a literal *int64 in Go? (2 answers) Closed 3 years ago . Go Newbie question: I am trying to init the following struct, with a default value. I know that it works if "Uri" is a string and not pointer to a string (*string). But i need this pointer for comparing two instances of the struct, where Uri would be nil if not set, e.g. when i demarshal content from a json file. But how can I initialize such a struct properly as a "static default"?