浅析Go语言编程当中映射和方法的基本使用

/* declare a variable, by default map will be nil*/
var map_variable map[key_data_type]value_data_type

/* define the map as nil map can not be assigned any value*/
map_variable = make(map[key_data_type]value_data_type)

package main

import "fmt"

func main {
   var coutryCapitalMap map[string]string
   /* create a map*/
   coutryCapitalMap = make(map[string]string)
  
   /* insert key-value pairs in the map*/
   countryCapitalMap["France"] = "Paris"
   countryCapitalMap["Italy"] = "Rome"
   countryCapitalMap["Japan"] = "Tokyo"
   countryCapitalMap["India"] = "New Delhi"
  
   /* print map using keys*/
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
  
   /* test if entry is present in the map or not*/
   captial, ok := countryCapitalMap["United States"]
   /* if ok is true, entry is present otherwise entry is absent*/
   if(ok){
      fmt.Println("Capital of United States is", capital) 
   }else {
      fmt.Println("Capital of United States is not present")
   }
}

package main

import "fmt"

func main {  
   /* create a map*/
   coutryCapitalMap := map[string] string {"France":"Paris","Italy":"Rome","Japan":"Tokyo","India":"New Delhi"}
  
   fmt.Println("Original map")  
  
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
  
   /* delete an entry */
   delete(countryCapitalMap,"France");
   fmt.Println("Entry for France is deleted") 
  
   fmt.Println("Updated map")  
  
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
}

import (
   "fmt"
   "math"
)

/* define a circle */
type Circle strut {
   x,y,radius float64
}

/* define a method for circle */
func(circle Circle) area() float64 {
   return math.Pi * circle.radius * circle.radius
}

func main(){
   circle := Circle(x:0, y:0, radius:5)
   fmt.Printf("Circle area: %f", circle.area())
}