assignment-operator

问题 We have equivalent assignment operators for all Logical operators, Shift operators, Additive operators and all Multiplicative operators. Why did the logical operators get left out? Is there a good technical reason why it is hard? 回答1: Why did the logical operators get left out? Is there a good technical reason why it is hard? They didn't . You can do &= or |= or ^= if you want. bool b1 = false; bool b2 = true; b1 |= b2; // means b1 = b1 | b2 The || and && operators do not have a compound form

问题 Here is an extract from item 56 of the book "C++ Gotchas": It's not uncommon to see a simple initialization of a Y object written any of three different ways, as if they were equivalent. Y a( 1066 ); Y b = Y(1066); Y c = 1066; In point of fact, all three of these initializations will probably result in the same object code being generated, but they're not equivalent. The initialization of a is known as a direct initialization, and it does precisely what one might expect. The initialization is

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Assignment operators in R: '=' and '<-' I'm using R 2.8.1 and it is possible to use both = and <- as variable assignment operators. What's the difference between them? Which one should I use? 回答1: From here: The operators <- and = assign into the environment in which they are evaluated. The operator <- can be used anywhere, whereas the operator = is only allowed at the top level (e.g., in the complete expression

问题 I have extended std::string to fulfil my needs of having to write custom function build into string class called CustomString I have defined constructors: class CustomString : public std::string { public: explicit CustomString(void); explicit CustomString(const std::string& str); explicit CustomString(const CustomString& customString); //assignment operator CustomString& operator=(const CustomString& customString); ... }; In the third constructor (copy constructor) and assignment operator,

问题 I am just starting C++. I am a bit confused about the return type of assignment and dereference operator. I am following the book C++ Primer. At various occasions, the author says that the return type of assignment operator is reference to the type of left hand operand but later on, he says that the return type is the type of the left hand operand. I have referred C++11 Standard Sec. 5.17, where the return type is described as "lvalue referring to left hand operand". Similarly, I can't figure

问题 So for binary operators on booleans, Java has & , | , ^ , && and || . Let's summarize what they do briefly here: JLS 15.22.2 Boolean Logical Operators &, ^, and | JLS 15.23 Conditional-And Operator && JLS 15.24 Conditional-Or Operator || For & , the result value is true if both operand values are true ; otherwise, the result is false . For | , the result value is false if both operand values are false ; otherwise, the result is true . For ^ , the result value is true if the operand values are

问题 There are lots of operations in std::ops, but there is nothing for a simple assignment. I'm coming from a C++ background, where there are copy constructor and assignment operator overloading that do the work for you. I need something like that in Rust. 回答1: You cannot overload assignment. Moving a variable from one location to another is a core component of Rust's ownership semantics and is not overridable. Another answer suggests that you custom-implement the Copy trait. This makes no sense,

问题 I am trying to copy a 2d array into another like so: reg [11:0] input_matrix [0:array_width - 1] [0:array_height - 1]; reg [11:0] output_matrix [0:array_width - 1] [0:array_height - 1]; always @(posedge clk) begin if(<some condition>) output_matrix <= input_matrix; end So, we have two 2D arrays of 12-bit values. I'd like to copy one into the other. This doesn't seem to be possible. Does anyone know the correct way to do this? Or, if not, explain why it's not possible? I can't see any reason

问题 I'm having trouble wrapping my head around the concept of an assignment operator, or at least creating them successfully. Copy Constructors aren't an issue for me; here is mine that its working: //copy constructor Set::Set(const Set &rhs){ _head = rhs._head; _tail = rhs._tail; //null, basically this object is 0 if(rhs._head == NULL){ _head = NULL; _tail = NULL; _size = 0; }else{ _head = new Elem(*rhs._head); _tail = new Elem(*rhs._tail); _size = rhs._size; Elem *prev = NULL; Elem *curr =

问题 I want to know the difference between these: my $a = 1; and my $a == 1; and my $a eq 1; 回答1: == is used when comparing numeric values. eq is used in comparing string values. = is the assignment operator, not a comparison operator. 回答2: eq is for testing string equality, == is the same thing but for numerical equality. For More Click Here 回答3: The last two statements do nothing, it's a good practice to use the directives: use warnings; use strict; for example: #!/usr/bin/perl use warnings; use