In c++--what does it mean?

The -- operator in C is a unary subtraction operator, used to subtract 1 from the value of a variable or expression. It has two forms: pre-decrement and post-decrement: pre-decrement (--): decrement by 1 first, and then use the value of the variable. Post-decrement (--): Use the value of the variable first, then decrement it by 1.

The -- operator in C

In the C programming language, the -- operator is a unary subtraction operator, used to reduce the value of a variable or expression by 1.

Usage:

<code class="cpp">--variable; // 前置递减
variable--; // 后置递减</code>

• Preceding decrement (--): Decrement the value of the variable by 1 before using it .
• Post-decrement (--): Use the value of the variable first, then decrement it by 1.

Difference:

• # Preceding decrement: Since 1 is decremented first, the returned value is decremented by 1 value.
• Post-decrement: Since the value is decremented by 1, the value returned is the value before decrementing by 1.

Example:

<code class="cpp">int x = 5;

// 前置递减
--x; // 减 1 并赋值给 x，此时 x 的值变为 4
cout << x << endl; // 输出：4

// 后置递减
x--; // 先使用 x 的值（5），再减 1，此时 x 的值变为 4
cout << x << endl; // 输出：4</code>

Priority:

-- Operators have higher priority than arithmetic operations symbols (e.g., -, *, /), but lower than brackets and unary signs (and -).

Note:

• -- Operators can only be applied to variables or modifiable expressions.
• When using leading decrement, make sure that the value of the variable does not become negative or exceed the range allowed by its data type.

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