[C language - zero basis _ study _ review _ lesson 5] operational properties of basic operators

The operational properties of basic operators

Ask every day ： The following illegal constants are

A ‘a’    B .5   C 1.2E2.0   D ‘\025’

Catalog

Basic arithmetic operators ：

Seeking remainder % Operator

Assignment expression ：

Compound assignment operator

Self addition and self subtraction and comma operators

The comma operator ：

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Basic arithmetic operators ：

+、-、*（ Equivalent to the multiplication sign in Mathematics x）、\( Equivalent to division in Mathematics )、%（ Mod ）

division /

1.0/2.0=0.5
1.0/2=0.5
1/2.0=0.5
1/2=0

Summary ：a And b One of them is real , The result is real . if a And b Is an integer , The result is an integer .

Seeking remainder % Operator

The object of the remainder operation must be an integer

5%2=1
5%-2=-1
2%5=2

Summary ： The operation to find the remainder must be an integer

There are negative numbers , The sign of the remainder is consistent with the divisor .（ And % The numbers on the left are the same ）

Precedence and associativity of operators ,

priority : （）  >   + ( Correct )   - ( Take the negative )  > *、/ 、%  >  +、-

associativity :

（）*、/ 、% 、+、- From left to right

+ ( Correct )   - ( Take the negative ) From right to left 1

Data type conversion ： Automatic conversion from low precision to high progress （ Last class cited the example of buying vegetables in the supermarket ）

1.0/2=0.5000000

Cast ： High precision to low precision cast

analysis ： If you go to the supermarket to buy vegetables , I bought a lot of vegetables and put them in a big bag. Later, I thought about it and put it together for environmental protection , Change a small bag. Because there are many dishes, you force the dishes into the small bag , But there are too many dishes to avoid being sent out of the bag .

form ：（ Type name ） expression

（int）5.2 // be equal to 5

Assignment expression ：

form ： Variable name = expression

int a=10;

The assignment is similar to filling a bottle with water .

priority ： Only higher than the comma operator （ Second from the bottom ）

associativity ： From right to left

explain ： According to the value of the priority expression , Let's assign it to the variable

Compound assignment operator

+=、-=、*=、/=、%=

priority ： Only higher than the comma operator （ Second from the bottom ）

associativity ： From right to left

a+=3;//a=a+3
a*=2;//a=a*2
a%=1;//a=a%1

Self addition and self subtraction and comma operators

form :++ Variable 、-- Variable 、 Variable ++、 Variable —

Pre value usage ++i --i

explain ： First, add the variable i The value of the add 1 Or minus 1, Then use variables i Value .

Post value usage i++、i—

explain ： First, we will use the variable i Value , Then add... To the value of the variable 1 Or minus 1

int i=1,j=1;
printf("%d,%d",++i,j++);// Input is 2,1

int i=1,j=1;
printf("%d,%d",--i,j--);// Input is 0,1

The comma operator ：

form ： Expression 1 、 Expression two 、… expression n

explain ： Evaluate from left to right , Expression n As the value of the entire comma expression

priority ： The minimum

associativity ： From left to right

int a=(1,2,3,4,5);//a=5;

C Language priority table

priority	Operator	Name or meaning	Use form	Combination direction	explain
1	[]	The array subscript	Array name [ Constant expression ]	Left to right	--
	()	parentheses	( expression ）/ Function name ( Formal parameter table )		--
	.	Member selection （ object ）	object . Member name		--
	->	Member selection （ The pointer ）	Object pointer -> Member name		--
2	-	Negative operator	- expression	Right to left	Monocular operator
	~	Bitwise negation operator	~ expression
	++	Self - increment operator	++ Variable name / Variable name ++
	--	Self - subtracting operator	-- Variable name / Variable name --
	*	Value operators	* Pointer to the variable
	&	Fetch address operator	& Variable name
	!	Logical nonoperator	! expression
	( type )	Cast	( data type ) expression		--
	sizeof	Length operator	sizeof( expression )		--
3	/	except	expression / expression	Left to right	Binocular operator
	*	ride	expression * expression
	%	remainder （ modulus ）	Integer expression % Integer expression
4	+	Add	expression + expression	Left to right	Binocular operator
	-	reduce	expression - expression
5	<<	Move left	Variable << expression	Left to right	Binocular operator
	>>	Move right	Variable >> expression
6	>	Greater than	expression > expression	Left to right	Binocular operator
	>=	Greater than or equal to	expression >= expression
	<	Less than	expression < expression
	<=	Less than or equal to	expression <= expression
7	==	be equal to	expression == expression	Left to right	Binocular operator
	！=	It's not equal to	expression != expression
8	&	Bitwise AND	expression & expression	Left to right	Binocular operator
9	^	Bitwise XOR	expression ^ expression	Left to right	Binocular operator
10	|	Press bit or	expression | expression	Left to right	Binocular operator
11	&&	Logic and	expression && expression	Left to right	Binocular operator
12	||	Logic or	expression || expression	Left to right	Binocular operator
13	?:	Conditional operator	expression 1? expression 2: expression 3	Right to left	Ternary operator
14	=	Assignment operator	Variable = expression	Right to left	--
	/=	Assign value after division	Variable /= expression		--
	*=	Multiply and assign	Variable *= expression		--
	%=	Assign a value after taking the module	Variable %= expression		--
	+=	Add and assign	Variable += expression		--
	-=	Value after subtraction	Variable -= expression		--
	<<=	Left shift assignment	Variable <<= expression		--
	>>=	Right shift after assignment	Variable >>= expression		--
	&=	Bitwise and post assignment	Variable &= expression		--
	^=	Assign a value after bitwise XOR	Variable ^= expression		--
	|=	Assign value by bit or after	Variable |= expression		--
15	,	The comma operator	expression , expression ,…	Left to right	--

If there are mistakes , Welcome to correct ！