reference

问题 Why ternary operator doesn't work with assignment by reference? $obj = new stdClass(); // Object to add $result = true; // Op result $success = array(); // Destination array for success $errors = array(); // Destination array for errors // Working $target = &$success; if(!$result) $target = &errors; array_push($target, $obj); // Not working $target = $result ? &$success : &$errors; array_push($target, $obj); 回答1: Here you go $target = ($result ? &$success : &$errors); Also your example has

问题 In my Java project, I have a vector of various types of Traders. These different types of traders are subclasses of the Trader class. Right now, I have a method that takes a Trader as an argument and stores it 50 or so times in the vector. I am having problems because storing the same object 50 times is just storing 50 references of the same object. I need to store 50 copies of the object. I've researched about implementing Clone, but I don't want the programmers defining a type of Trader to

问题 When I run the code, I get an error "failed adding to JNI local ref table has 512 entries" This is my code: jstring pJNIData = pJNIEnv->NewStringUTF ( variables[0].GetStringValue() ); pJNIEnv->CallStaticVoidMethod ( pJNIActivityClass, pJNIMethodIDStartTime, pJNIData ) ; pJNIEnv->DeleteLocalRef(pJNIData); I have read several suggestions, but none of them work! In spite of the DeleteLocalRef , it fails to works. The function is used in a profiler that literally calls all the functions... 回答1: I

问题 I'm currently reading about C++ , and I read that when using return by reference I should make sure that I'm not returning a reference to a variable that will go out of scope when the function returns. So why in the Add function the object cen is returned by reference and the code works correctly?! Here is the code: #include <iostream> using namespace std; class Cents { private: int m_nCents; public: Cents(int nCents) { m_nCents = nCents; } int GetCents() { return m_nCents; } }; Cents& Add

问题 I was playing around with Rust closures when I hit this interesting scenario: fn main() { let mut y = 10; let f = || &mut y; f(); } This gives an error: error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements --> src/main.rs:4:16 | 4 | let f = || &mut y; | ^^^^^^ | note: first, the lifetime cannot outlive the lifetime as defined on the body at 4:13... --> src/main.rs:4:13 | 4 | let f = || &mut y; | ^^^^^^^^^ note: ...so that closure can access

问题 I was playing around with Rust closures when I hit this interesting scenario: fn main() { let mut y = 10; let f = || &mut y; f(); } This gives an error: error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements --> src/main.rs:4:16 | 4 | let f = || &mut y; | ^^^^^^ | note: first, the lifetime cannot outlive the lifetime as defined on the body at 4:13... --> src/main.rs:4:13 | 4 | let f = || &mut y; | ^^^^^^^^^ note: ...so that closure can access

问题 I'll illustrate my question with code: #include <iostream> void PrintInt(const unsigned char*& ptr) { int data = 0; ::memcpy(&data, ptr, sizeof(data)); // advance the pointer reference. ptr += sizeof(data); std::cout << std::hex << data << " " << std::endl; } int main(int, char**) { unsigned char buffer[] = { 0x11, 0x11, 0x11, 0x11, 0x22, 0x22, 0x22, 0x22, }; /* const */ unsigned char* ptr = buffer; PrintInt(ptr); // error C2664: ... PrintInt(ptr); // error C2664: ... return 0; } When I run

问题 I'll illustrate my question with code: #include <iostream> void PrintInt(const unsigned char*& ptr) { int data = 0; ::memcpy(&data, ptr, sizeof(data)); // advance the pointer reference. ptr += sizeof(data); std::cout << std::hex << data << " " << std::endl; } int main(int, char**) { unsigned char buffer[] = { 0x11, 0x11, 0x11, 0x11, 0x22, 0x22, 0x22, 0x22, }; /* const */ unsigned char* ptr = buffer; PrintInt(ptr); // error C2664: ... PrintInt(ptr); // error C2664: ... return 0; } When I run

问题 So I am new to C# and I am having difficulty understanding out . As opposed to just returning something from a function using System; class ReturnTest { static double CalculateArea() { double r=5; double area = r * r * Math.PI; return area; } static void Main() { double output = CalculateArea(); Console.WriteLine("The area is {0:0.00}", output); } } compare to this using System; class ReturnTest { static void CalculateArea(out double r) { r=5; r= r * r * Math.PI; } static void Main() { double

问题 I'm developing a LALG compiler to my college course on Java 1.6. So I did a types class and grammar class. EnumTypes public enum EnumTypes { A("OLA"), B("MUNDO"), C("HELLO"), D("WORLD"), /** * The order below is reversed on purpose. * Revert it and will you get a NULL list of types furder. */ I(EnumGrammar.THREE), H(EnumGrammar.TWO), F(EnumGrammar.ONE), E(EnumGrammar.ZERO); private String strValue; private EnumGrammar enumGrammarValue; private EnumTypes(String strValue) { this.strValue =