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The third level of C language punch in
2022-07-06 02:16:00 【HTTPS 443୧⍤⃝】
One 、 Cast expression
form :( Type name ) expression
function : Converts the value of an expression to the specified data type
(double) 1/2 The value of is 0.5 ( As mentioned in the last section 1/2 It's two integers Should the 0 Because there is a double, The value is decimal 0.5, amount to (double)1/2 Equivalent to 1.0/2)
The level of cast takes precedence over division
This table describes the transformation rules more vividly
Two 、 Assignment expression
form : Variable name = expression
On the left is a variable name , Get the value of an expression on the right , Assign the value of the expression to a variable , Its combination is
From right to left , Its priority is only higher than comma operator . The value of the assignment expression is the new value obtained by the leftmost variable .
Simply put, it's the left A variable , On the right is an equation . such as :a=2+7/3
(1) Compound assignment expression
such as n+=1 Equivalent to n=n+1
n*=m+3 Equivalent to n=n*(m+3)
Yes : = += -= /= %= &= ^= wait associativity : From right to left
(2) Type conversion in assignment operation
int x; x=6.5; //x Integers 6, Here is a transformation , Convert to be consistent with the type of variable double y; y=6; //y by 6.0, Here is a transformation , Convert to be consistent with the type of variable
3、 ... and 、 Auto increment and auto decrement operator
Self adding 、 The subtraction operator is ++ and --. Self adding ( reduce ) Operator in front , First increase ( reduce ) After use ; Self adding ( reduce ) Operator after , Use first and then increase ( reduce ). The combination direction of operators is from right to left ,-k++ Equivalent to -(k--).
Self adding ( reduce ) There are often two operations in the operation : Calculate the value of the expression and the value of the variable .
set up k=3, Calculate the value of the following assignment expression and calculate the value of the variable
expression x Value k Value The value of the assignment expression x=k++ 3 4 3 x=++k 4 4 4 x=k-- 3 2 3 x=--k 2 2 2 As can be seen from the table :++ Must make k increase 1,-- Must make k reduce 1, Because it is an assignment expression , therefore x The value of is interlinked with the value of the expression
Four 、 Comma operators and comma expressions
form : expression 1, expression 2,....., expression n
Combination direction : From left to right
Operational rules : So let's evaluate the expression 1 Value , And then evaluate the expression 2 Value , And then calculate the expression 3 Value ,..... Finally, calculate the expression n Value , expression n The value of is the value of the entire comma expression
The comma expression has the lowest priority , Lower than assignment
int x=8,y=12,z=14 x++,y=z++,z=++x; y=x%z--; // Last x=10 y=0,z=9
answer :
The original x=8 You can see that from the top Yes x++ Add a ,++x Once again, , Total increase 2 Time , Namely 8+2=10
The original y=12 y=X%z-- here x=10 z=10 because z=++x ,z-- Is the suffix with the previous value 10 To participate in the calculation , therefore 10%10=0 ,y Is equal to 0
The original z=14 First, y=z++ ,z=15 also z=++x ,z be equal to 10, Last z-- Say with z=9
Answer of last issue :
#include<stdio.h>
void main()
{
double a,b,c; // Define three real numbers
double sum,aver; //sum Storage and ,aver Store the average
scanf("%lf%lf%lf",&a,&b,&c); // Input 3 A real number
sum=a+b+c; // Calculation 3 Sum of numbers
aver=(a+b+c)/3; // Calculation 3 The average of the numbers
getchar();
getchar();
}
This assignment
1. Enter the of the triangle 3 Strip side length , Find the area of three triangles ( Query the formula on the Internet , I will use the square function sqrt, File header is required math.h)
2. Input 2 Number , In exchange for 2 The value of the number
for example : x=2 ,y=3 After exchanging x=3,y=2
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