pass-by-reference

来源： https://stackoverflow.com/questions/63476678/pointer-to-pointer-in-linked-list

来源： https://stackoverflow.com/questions/2610972/why-can-i-change-structs-int-property-from-method-without-specifying-ref

问题 Motivated by this question, I compared two different versions of an implementation of a binary operator+ in terms of operator+= . Consider we are inside the definition of class X . Version 1 friend X operator+(X lhs, const X& rhs) { lhs += rhs; return lhs; } Version 2 friend X operator+(const X& lhs, const X& rhs) { X temp(lhs); temp += rhs; return temp; } friend X operator+(X&& lhs, const X& rhs) { lhs += rhs; return std::move(lhs); } Where, in both cases, operator+= is defined as follows: X

问题 As per a suggestion in the comments from here, I am starting a thread to learn the reference technique for passing values and variables from form to form, also discussed here and here. As a side note, to the best of my knowledge, it's not the technique referred to here and here. Those previous questions demonstrated that the following code in the called form, sets up this technique. Dim prevForm As Form Private Sub Form_Load() Set prevForm = Screen.ActiveForm End Sub For an Access beginner

问题 int main() { // Complete the program string a,b; getline(cin,a); getline(cin,b); cout<<a.size()<<" "; cout<<b.size(); string c=a+b; cout<<endl<<c; swap(a[0],b[0]); cout<<endl<<a<<" "<<b; return 0; } void swap(string s1,string s2){ string temp=s1; s1=s2; s2=temp; } Well the target is to swap the first element of both strings, but I created a general function for that and even got it right. But, unexpectedly, I didn't use pass by reference or pointer! Even then, the changes are permanent when I

问题 Working with Futures in Dart, I've come across an interesting issue. import 'dart:async'; class Egg { String style; Egg(this.style); } Future cookEggs(List<Egg> list) => new Future(() => ['omelette','over easy'].forEach((_) => list.add(new Egg(_))) ); Future cookOne(Egg egg) => new Future(() => egg = new Egg('scrambled')); void main() { List<Egg> eggList = new List(); Egg single; cookEggs(eggList).whenComplete(() => eggList.forEach((_) => print(_.style)); cookOne(single).whenComplete(() =>

问题 I just read this: In C++ (and C99), we can pass by reference, which offers the same performance as a pointer-pass. So I tried this simple code: #include <stdio.h> void blabla(int& x){ x = 5; } int main(){ int y = 3; printf("y = %d\n", y); blabla(y); printf("y = %d\n", y); } The output was: gcc test.c -o test -std=c99 test.c:3:16: error: expected ';', ',' or ')' before '&' token test.c: In function 'main': test.c:10:2: warning: implicit declaration of function 'blabla' Now I'm confused. Is

问题 I decided to see if assigning a reference to a member would make a member a reference. I wrote the following snippet to test it. There's a simple class Wrapper with an std::string as a member variable. I take take a const string& in the constructor and assign it to the public member variable. Later in the main() method I modify the member variable but the string I passed to the constructor remains unchanged, how come? I think in Java the variable would have changed, why not in this code

问题 I don't understand the results of the following linqpad query in C#. The comments should explain where I am confused. void Main() { Dictionary<string, testClass> test = new Dictionary<string, testClass>(); string key = "key"; testClass val = null; test.Add(key, val); val = new testClass(); test[key].Dump(); //returns null. WHAT? I just set it!!! test[key] = val; val.Text = "something"; // returns val object, with Text set to "Something". // If the above didn't work, why does this work? test

问题 I'm looking for a way to use a function as an argument to another function in GLSL. In regular C, it can be simulated by passing a function pointer as a function argument. It also seems that other languages (like HLSL) now provide ways to deal with high-level constructs like higher-order functions, or can simulate them with clever use of HLSL structures. unfortunately I'm stuck with GLSL for now, and I can't find any way to simulate higher-order functions. Is it really impossible in current