区别＆QUOT; INT I = 1,2,3＆QUOT;和＆QUOT; INT I =（1,2,3）＆QUOT; - 逗号分隔符变量声明 [英] Difference between "int i=1,2,3" and "int i=(1,2,3)" - variable declaration with comma operator

问题描述

1. INT I = 1,2,3;




2. INT I =（1,2,3）;




3. INT I; I = 1,2,3;

什么是这些语句之间的区别？我不能让任何特定的理由。

解决方案

 声明1结果：编译错误。
 

=经营者有较高的precedence比，运营商。
逗号充当这里的分隔符。编译器创建一个整型变量'我'和'1'对其进行初始化。
编译器未能创建整数变量'2'为'2'是不是一个有效indentifer

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 声明2结果：I = 3
 

（）经营者具有较高的precedence比=。所以，第一，支架运营商进行评估。从左至右'（）'操作符被操作。但它始终是最后那个被分配的结果。

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 声明3：结果：I = 1
 

=经营者有较高的precedence比，运营商。所以'我'会被'1'初始化。 '2'和'3'只是不断前​​pression。所以没有任何效果。

1. int i=1,2,3;

2. int i=(1,2,3);

3. int i; i=1,2,3;

What is the difference between these statements? I can't get to any particular reason for it.

解决方案

Statement 1 Result : Compile error.

'=' operator has higher precedence than ',' operator. comma act as a separator here. the compiler creates an integer variable 'i' and initializes it with '1'. The compiler fails to create integer variable '2' as '2' is not a valid indentifer.

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Statement 2 Result: i=3

'()' operator has higher precedence than '='. So , firstly, bracket operator is evaluated. '()' operator is operated from left to right. but it is always the result of last that gets assigned.

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Statement 3: Result: i=1

'=' operator has higher precedence than ',' operator. so 'i' gets initialized by '1'. '2' and '3' are just constant expression. so have no effect .

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