[go language question brushing chapter] go conclusion chapter | introduction to functions, structures, interfaces, and errors

Preface

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Q1： function - Factorial of numbers

Problem description ： The factorial of a positive integer （factorial） Is the product of all positive integers less than or equal to the number , also 0 The factorial of is 1. Natural number n The factorial writing of n!.

Related knowledge ：
1、 recursive , It is to call itself in the process of running . A function calls itself , It's called a recursive function . The conditions that constitute recursion ： The sub problem must be the same thing as the original problem , And it's simpler . You can't call itself unlimited , There must be an exit , Reduction to non recursive state processing .

Instance input ：2
Instance output ：2

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param i int integer   Numbers  * @return int integer  */
func factorial( i int ) int {
    
	// write code here
	if i == 0{
    
		return 1
	}
	return i * factorial(i-1)
}

Q2： function - The absolute value

Problem description ： Define a function , The function of the function is to give a number , Returns the absolute value of the number .

Related knowledge ：
1、 Definition of function ： The function declaration contains a function name , parameter list , Return value list and function body . If the function does not return a value , The returned list can be omitted . The function starts with the first statement , Until the execution of return Statement or the last statement that executes a function . Functions can have no arguments or accept multiple arguments . Note that the type is after the variable name . When two or more consecutive function named arguments are of the same type , Except for the last type , Anything else can be omitted . Function can return any number of return values . Use keywords func Defined function , The left brace still cannot start another line .

func function_name( [parameter list] ) [return_types] {
    
    The body of the function 
}

2、 Function call ： When creating a function , You define what the function needs to do , Perform the specified task by calling this function . Call function , Pass arguments to the function , And the return value
3、Go Function can return multiple values ,"_" identifier , Used to ignore a return value of a function Go The return value of can be named , And it's just like a function at the beginning of a variable . The name of the return value should have some meaning , Can be used as a document . Without parameters return Statement returns the current value of each return variable .

Instance input ：-1
Instance output ：1

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param x int integer  * @return int integer  */
func absfunc(x int) int {
    
	// write code here
	if x < 0 {
    
		return -x
	}
	return x
}

Q3： function - Add, subtract, multiply and divide

Problem description ： Define a function , Implement input a,b Two Numbers , Returns the sum of two numbers , Bad , The product of , merchant , remainder . Then it is stored in slices in turn , Finally back to .

Related knowledge ：
1、Go Functions in support of multiple return values , But when a function has multiple return values , If one or more of the return values do not want to be used , You can underline _ To discard these return values . For example, the following f1 The function returns two values , When the function is called , The second return value is discarded b, Only the first return value is retained a Assigned to a variable a.

Instance input ：2,2
Instance output ：[4,0,4,1,0]

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param a int integer  * @param b int integer  * @return int Integer one-dimensional array  */
func operate( a int ,  b int ) []int {
    
	// write code here
	var ans []int
	ans = append(ans, a+b)
	ans = append(ans, a-b)
	ans = append(ans, a*b)
	ans = append(ans, a/b)
    ans = append(ans, a % b)
	return ans
}

Q4： Structure - Student information 1

Problem description ： Each student has the following information ： full name name, Gender sex, Age age, fraction score, Define a structure Student, To express Xiao Ming's information , Xiao Ming's information is as follows ： full name ： Xiao Ming , Gender ：true, Age ：23, fraction ：88

Related knowledge ：
1、Go The basic data types in language can represent the basic properties of some things , But when we want to express all or part of the attributes of a thing , At this time, a single basic data type is obviously unable to meet the demand ,Go The language provides a custom data type , It can encapsulate multiple basic data types , This type of data is called a structure , English name struct. That is, we can go through struct To define your own type .
2、 A structure consists of a series of named elements , These elements are also called fields , Each field has a name and a type .
3、 The purpose of a structure is to aggregate data , In order to be able to operate these data more easily .
4、 Definition of structure ： Structure definition needs to use type and struct sentence .struct Statement to define a new data type , A structure has one or more members .type Statement sets the name of the structure . The format of the structure is as follows ：
type Type name struct {
Field name Field type
Field name Field type
…
}
Type name ： Identifies the name of the custom structure , Cannot repeat in the same package .
Field name ： Represents the structure field name . Field names in structures must be unique .
Field type ： Represents the specific type of structure field .
5、 Access members of the structure ： If you want to access structure members , You need to use a dot . The operator .

Sample input ： nothing
Sample output ：

 Xiao Ming 
true
23
88

Case code ：

import "fmt"
type stu struct {
    
	name  string
	sex   bool
	age   int
	score int
}
func main() {
    
	a := stu{
    
		name:  " Xiao Ming ",
		age:   23,
		sex:   true,
		score: 88,
	}
	fmt.Println(a.name)
	fmt.Println(a.sex)
	fmt.Println(a.age)
	fmt.Println(a.score)
}

Q5： Structure - Student information 2

Problem description ： Each student has the following information ： full name name, Gender sex, Age age, fraction score, Address information address, among address The address information also includes the city city, Province province Etc , Define a structure Student, To express Xiao Ming's information , Xiao Ming's information is as follows ： full name ： Xiao Ming , Gender ：true, Age ：23, fraction ：88,province： Hunan province ,city： Changsha City .
Output and print Xiaoming information in turn

Related knowledge ：
1、 One structure can be nested with another structure or structure pointer .

Sample input ：
Sample output ：

 Xiao Ming 
true
23
88
 Hunan province 
 Changsha City 

Case code ：

import (
	"fmt"
)
type address struct {
    
	city     string
	prov***ring
}
type stu struct {
    
	name  string
	sex   bool
	age   int
	score int
	add   address
}
func main() {
    
	a := stu{
    
		name:  " Xiao Ming ",
		age:   23,
		sex:   true,
		score: 88,
		add: address{
    
			city:     " Changsha City ",
			province: " Hunan province ",
		},
	}
	fmt.Println(a.name)
	fmt.Println(a.sex)
	fmt.Println(a.age)
	fmt.Println(a.score)
	fmt.Println(a.add.province)
	fmt.Println(a.add.city)
}

Q6： Interface - Animals and tigers

Problem description ： Define an animal interface , This interface has sleep,eat Method , Define the tiger to implement the animal interface , Tiger sleep Method output "tiger sleep",eat Method output "tiger eat", Finally, call tiger's sleep,eat Method .

Related knowledge ：
1、 stay Go Interface in language （interface） It's a type of , An abstract type .interface It's a group. method Set , yes duck-type programming A manifestation of . Interfaces do things like defining a protocol （ The rules ）, As long as a machine has the function of washing and drying , I call it a washing machine . Don't care about attributes （ data ）, Only care about behavior （ Method ）.
2、 Interface （interface） Defines the behavior of an object , Only define the specification, not implement , Specification details are implemented by specific objects . Interface oriented programming
3、 An interface is a collection of one or more method signatures .
4、 Any type of method set as long as it has the interface ’ All corresponding methods ’ Signature . It means it's “ Realization ” The interface , There is no need to explicitly declare which interface is implemented on the type . This is called Structural Typing. The so-called correspondence method , Means having the same name 、 parameter list ( Parameter names are not included ) And the return value . Of course , This type can also have other methods .
5、 Interface has only method declarations , It didn't come true , No data fields . Interfaces can be embedded anonymously into other interfaces , Or embedded in the structure .
6、type Interface type name interface{
Method name 1( parameter list 1 ) Return value list 1
Method name 2( parameter list 2 ) Return value list 2
…
}

Sample input ： nothing
Sample output ：

sleep
eat

Case code ：

import "fmt"
type animal interface {
    
	sleep()
	eat()
}
type tiger struct {
    
}

func (t tiger) sleep() {
    
	fmt.Println("sleep")
}
func (t tiger) eat() {
    
	fmt.Println("eat")
}
func main() {
    
	var t animal = tiger{
    }
	t.sleep()
	t.eat()
}

Q7： error - Network delay

Problem description ： Realization erro Interface , Customize an error , This error is thrown " Network delay " error . Enter the delay number of the network , If the delay is greater than 100 Network delay , And back to

Related knowledge ：
1、 error ：Go The language provides a very simple error handling mechanism through a built-in error interface .

 type error interface {
    
        Error() string
        }

2、 Realization error Interface type to generate error messages , Function usually returns error information in the last return value . Use errors.New Can return an error message

Sample input ：150
Sample output ：“ Network delay ”

Case code ：

import "errors"
type error interface {
    
	Error() string
}
func Error() string {
    
	return " Network delay "
}
func defineerr(ping int) string {
    
	// write code here
	if ping > 100 {
    
		errors.New(" Network delay ")
		return " Network delay "
	}
	return ""
}

Q8： error - Abnormal body temperature

Problem description ： Implement a function , The function of this function is Given a float The type variable represents a person's body temperature , If someone's temperature is greater than 37.5, Throw out " Abnormal body temperature ", And the output .

Related knowledge ：
1、Go You can throw a panic It's abnormal , And then in defer Pass through recover Catch this exception , And then deal with it normally .

Sample input ：38.000000
Sample output ：“ Abnormal body temperature ”

Case code ：

//import "fmt"
/** *  The class name in the code 、 Method name 、 The parameter name has been specified , Do not modify , Return the value specified by the method directly  * @param t double floating-point   Temperature  * @return string character string  */
func temperature(t float64) (ans string) {
    
	// write code here
	ans = ""
	defer func() {
    
		err := recover()
		if err != nil {
    
			ans = " Abnormal body temperature "
		}
	}()
	if t > 37.5 {
    
		panic(" Abnormal body temperature   Pop up warning ！")
	}
	return ans
}

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