What does += mean in c++

The = operator in C is a compound assignment operator that adds a value to a variable or object, which is equivalent to the variable = value. The syntax is variable = expression, where the variable is the mutable object and the expression is the added value. It supports implicit type conversions and can also be used to update members of a structure or class.

The = operator in C

In C, the = operator is a compound assignment operator. Used to add a value to a variable or object. Its semantics are equivalent to the following operations:

变量 += 值;

Syntax

= The syntax of the operator is:

变量 += 表达式;

where:

• Variable is the variable or object to be updated.
• Expression is the value or expression to be added to the variable.

Examples

Here are some examples of the = operator:

int x = 10;
x += 5; // x 现在等于 15
std::string name = "John";
name += " Doe"; // name 现在包含 "John Doe"

Type conversion

If the variable and expression have different types, the compiler will perform an implicit type conversion to match the variable's type. For example:

double x = 1.5;
x += 1; // x 现在等于 2.5（隐式将整型 1 转换为 double）

Advanced usage

The = operator can also be used to update members of a structure or class:

struct Point {
  int x;
  int y;
};

Point point = {1, 2};
point.x += 3; // point.x 现在等于 4

Notes

The = operator can only be used to update mutable objects, that is, variables or objects that have the assignment (=) operator.

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