This is a new pattern matching feature which was introduced in C# 8.0 and is called property pattern. In this particular case it is used to check that object is not null, example from the linked article: static string Display(object o) => o switch { Point { X: 0, Y: 0 } p => “origin”, … Read more
It’s the “null coalescing operator”, added in php 7.0. The definition of how it works is: It returns its first operand if it exists and is not NULL; otherwise it returns its second operand. So it’s actually just isset() in a handy operator. Those two are equivalent1: $foo = $bar ?? ‘something’; $foo = isset($bar) … Read more
The compiler can evaluate the function printcbase() as this: void printcbase(cbase* b ){ int a = b->FooA(); // line 1 int b = b->FooB(); // line 2 std::cout << a; // line 3 std::cout << b; // line 4 stc::cout << std::endl; } or some of many permutatins of lines marked as 1 – 4. … Read more
Yes and No. It depends on which version of C++, you’re using. C++98 and C++03 do not support explicit type conversion operators But C++11 does. Example, struct A { //implicit conversion to int operator int() { return 100; } //explicit conversion to std::string explicit operator std::string() { return “explicit”; } }; int main() { A … Read more
Yes. Any operators classified as comparisons can be chained. From the language reference: Formally, if a, b, c, …, y, z are expressions and op1, op2, …, opN are comparison operators, then a op1 b op2 c … y opN z is equivalent to a op1 b and b op2 c and … y opN … Read more
Ternary expressions, like any expression, have a type that is determined by the compiler. If the two sides of the ternary expression have what looks like different types, then the compiler will try and find a common base type using the least ambiguous of the two options. In your case, the -1 is least ambiguous, … Read more
You cannot overload operator [][], but the common idiom here is using a proxy class, i.e. overload operator [] to return an instance of different class which has operator [] overloaded. For example: class CMatrix { public: class CRow { friend class CMatrix; public: int& operator[](int col) { return parent.arr[row][col]; } private: CRow(CMatrix &parent_, int … Read more
Implement the operator overloading outside of the class: class Num { public: Num(int i) { this->i = i; } int i; }; int operator+(int i, const Num& n) { return i + n.i; }
the answer to my question is not to use let (or shift, or…) but to use i=$((i+1)) when trying to check a bash script by setting ‘exit on non-zero status code‘ with set -e The bash manual states that set -e has the effect of ‘Exit immediately if a simple command exits with a non-zero … Read more
The behaviour is specified in JLS – Conditional Operator: If one of the second and third operands is of primitive type T, and the type of the other is the result of applying boxing conversion (ยง5.1.7) to T, then the type of the conditional expression is T. Emphasis mine. So, in the 2nd case: Float … Read more