C language operators and expressions

Catalog

Preface

Assignment operator 、 Assignment expression

1. Assignment operator

2. Assignment expression

3. Assignment statement

4. usage

Cast cast character

1. Automatic conversion

2. Coercive transformation

Arithmetic operator 、 Arithmetic expressions

1. Arithmetic operator

2. Arithmetic expressions

Auto increment and auto decrement operator

sizeof Operator

Compound assignment operator

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Preface

Operators are used to process data . Using operators to connect variables and constants conforms to C Expressions of linguistic grammar rules are called expressions . Single constant 、 A variable or function is a simple expression .

It is divided according to the number of operands carried by the operator ,C There are three categories of operators in languages ：

Monocular operator ： An operator with only one operand . Such as ：++ Operator .

Binocular operator ： Operator with two operands . Such as ：+、-、*、/、% Operator .

Ternary operator ： Operator with three operands . Such as ：？ Operator .

Assignment operator 、 Assignment expression

1. Assignment operator

Symbol : =

function ： Assign the value of the expression on the right to the variable on the left . The left and right sides here are not interchangeable .

Binocular operator ： There are operands on both sides .

for example ：

int a,b,c;
a=1314;//a=1314
b=a;//b=1314
c=a+b;//c=2628

2. Assignment expression

Let's look at an example ：

a=520

Be careful ： Expressions have values , The value of the assignment expression is the value of the assigned variable . The above example a=520 The value of this assignment expression is a Value 520.

3. Assignment statement

C Language policy , Any expression with a semicolon at the end becomes a statement .

So assignment expression plus semicolon is assignment statement .

Look at the example again ：

a=365;

4. usage

Continuous assignment ： Right binding , That is, to operate from right to left .

Look at examples ：

a=b=c=d=666;

Cast cast character

1. Automatic conversion

When = When the data types on both sides are different ,C Language will make = The data type of the expression value on the right becomes = The data type of the variable on the left .

Look at examples ：

int a=3.65;//a=3

2. Coercive transformation

Change if you want to ：

float a=1.79,b=2.1;

that (int)a The value is 1, Yes , It's rounding down ,(int)(a+b) Then it is a+b The result turns into int type , Its value is 3.

Arithmetic operator 、 Arithmetic expressions

1. Arithmetic operator

Symbol : +  -  *  /  %

function ： I believe you can add （+）、 reduce （-）、 ride （*）、 except （/） You can understand , Remainder （%） What is it? ？

According to my habit , Let's take a look at the examples first ：

int a=10%3;//a=1
int b=9%3;//b=0

It is often used in the follow-up study , There is another thing called mold taking , These two mean the same , Is the remainder of the division of two numbers . The remainder is very easy to use , It's a skill job .

Be careful ：C Language policy , The quotient of the division of two integers is still an integer , Rounding down .

for example ：5/2 The result is 2, If you want to get 2.5, Should be written as 5.0/2 or 5/2.0.

Be careful ：% It can only be used for integer operations .

2. Arithmetic expressions

An expression whose operators are all arithmetic operators is called an arithmetic expression . I believe everyone can understand .

Auto increment and auto decrement operator

Symbol : ++  - -

seeing the name of a thing one thinks of its function , Look at the example , Feel for yourself ：

int i=j=k=l=6;
i++;//i=7
j--;//j=5
++k;//k=7
--l;//l=5

Okay , I believe you should have doubts in your mind . Here's an explanation ：

Prepositive operations ：++i、--i： Increase or decrease before operation .

Post operation ：i++、i--： Calculate first and then increase or decrease .

Look at examples ：

int i=j=k=l=6,look;
look=i++;//look=6,i=7
look=j--;//look=6,j=5
look=++k;//look=7,k=7
look=--l;//look=5,l=5

Be careful ：++ and -- Operators can only be used with variables , Cannot be used for constants and expressions .

            Two + And two - There is no space between .

            Auto increment and auto decrement are often used in loop statements .

            You cannot use... On a variable consecutively , Such as ++i++ It's illegal. .

sizeof Operator

Symbol ：sizeof

function ： Get the memory occupied by variables and data types （ Number of bytes ）.

Be careful ：sizeof in size and of There is no space between .

Compound assignment operator

Symbol ：+=、-=、*=、/=、%=、&=、|=、^=、<<=、>>=

function ： See the following example ：

a+=1 Equivalent to a=a+1

a*=2 Equivalent to a=a*2