Cplusplus 简明教程

C++ decision making statements

决策制定结构要求程序员指定程序要评估或测试的一个或多个条件，以及在确定条件为真时要执行的语句，以及在确定条件为假时要执行的其他语句（可选）。

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

以下是大多数编程语言中常见的典型决策结构的一般形式 −

Following is the general form of a typical decision making structure found in most of the programming languages −

cpp decision making

C++ 编程语言提供以下类型的决策制定语句。

C++ programming language provides following types of decision making statements.

Sr.No

Statement & Description

1

if statementAn ‘if’ statement consists of a boolean expression followed by one or more statements.

2

if…​else statementAn ‘if’ statement can be followed by an optional ‘else’ statement, which executes when the boolean expression is false.

3

switch statementA ‘switch’ statement allows a variable to be tested for equality against a list of values.

4

nested if statementsYou can use one ‘if’ or ‘else if’ statement inside another ‘if’ or ‘else if’ statement(s).

5

nested switch statementsYou can use one ‘switch’ statement inside another ‘switch’ statement(s).

The ? : Operator

我们在上一章中涵盖了 conditional operator “? :” ，可用于替换 if…​else 语句。其一般形式如下所示 −

We have covered conditional operator “? :” in previous chapter which can be used to replace if…​else statements. It has the following general form −

Exp1 ? Exp2 : Exp3;

Exp1、Exp2 和 Exp3 是表达式。注意冒号的使用和位置。

Exp1, Exp2, and Exp3 are expressions. Notice the use and placement of the colon.

“?”表达式的值这样确定：计算 Exp1。如果其为真，则计算 Exp2，其将成为整个“?”表达式的值。如果 Exp1 为假，则计算 Exp3，其值将成为表达式的值。

The value of a ‘?’ expression is determined like this: Exp1 is evaluated. If it is true, then Exp2 is evaluated and becomes the value of the entire ‘?’ expression. If Exp1 is false, then Exp3 is evaluated and its value becomes the value of the expression.