go语言中有一些比较常用的内建函数，在这篇文章中将会进行简单的介绍。
内建函数
| 函数名 |
说明 |
备注 |
| close |
关闭channel |
仅用于channel通讯 |
| delete |
从map中删除实例 |
map操作 |
| len |
返回字符串，slice和数组的长度 |
可用于不同的类型 |
| cap |
返回容量 |
可用于不同的类型 |
| new |
内存分配 |
用于各种类型 |
| make |
内存分配 |
仅用于chan/slice/map |
| copy |
复制slice |
slice操作 |
| append |
追加slice |
slice操作 |
| panic |
报告运行时问题 |
异常处理机制 |
| recover |
处理运行时问题 |
异常处理机制 |
| print |
内建打印函数 |
主要用于不引入fmt的时候的调试，实际使用时建议使用标准库fmt |
| println |
内建打印函数 |
主要用于不引入fmt的时候的调试，实际使用时建议使用标准库fmt |
| complex |
构造复数类型 |
复数操作 |
| real |
抽出复数的实部 |
复数操作 |
| imag |
抽出复数的虚部 |
复数操作 |
len & cap
| 对象 |
len返回值 |
cap返回值 |
| 数组 |
数组元素个数 |
数组元素个数 |
| 指向数组的指针 |
数组元素个数 |
数组元素个数 |
| slice |
元素个数 |
slice的最大size >=len(slice) |
map操作：delete
例子代码
[root@liumiaocn goprj]# cat basic-buildin1.go
package main
import "fmt"
func main() {
m1 := make(map[string]int)
m1["Mon"] = 1
m1["Tue"] = 2
m1["Wed"] = 3
fmt.Println("before delete : m1=", m1, "len(m1)=", len(m1))
println("delete element by using key Tue")
delete(m1, "Tue")
fmt.Println("after delete : m1=", m1, "len(m1)=", len(m1))
}
[root@liumiaocn goprj]#
执行结果
[root@liumiaocn goprj]
before delete : m1= map[Mon:1 Tue:2 Wed:3] len(m1)= 3
delete element by using key Tue
after delete : m1= map[Mon:1 Wed:3] len(m1)= 2
[root@liumiaocn goprj]
slice操作
例子代码
[root@liumiaocn goprj]# cat basic-buildin2.go
package main
import "fmt"
func main() {
a1 := new([10]int)
a1[4] = 5
a1[7] = 8
fmt.Println("a1= ", a1, "len(a1)=", len(a1), " cap(a1)=", cap(a1))
s1 := make([]int, 5, 10)
s1[0] = 5
s1[4] = 2
s2 := make([]int, 5, 10)
s2[0] = 1
s2[4] = 3
fmt.Println("before copy :s1= ", s1, "len(s1)=", len(s1), " cap(s1)=", cap(s1))
fmt.Println("before copy :s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
println("copy(s2,s1)")
copy(s2, s1)
fmt.Println("after copy :s1= ", s1, "len(s1)=", len(s1), " cap(s1)=", cap(s1))
fmt.Println("after copy :s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
println("reset")
s2[0] = 1
s2[4] = 3
fmt.Println("after reset:s1= ", s1, "len(s1)=", len(s1), " cap(s1)=", cap(s1))
fmt.Println("after reset :s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
println("append(s2,20)")
s2 = append(s2, 6)
fmt.Println("after append:s1= ", s1, "len(s1)=", len(s1), " cap(s1)=", cap(s1))
fmt.Println("after append:s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
s2 = append(s2, 7)
s2 = append(s2, 8)
s2 = append(s2, 9)
s2 = append(s2, 10)
fmt.Println("after append:s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
s2 = append(s2, 11)
fmt.Println("after append:s2= ", s2, "len(s2)=", len(s2), " cap(s2)=", cap(s2))
}
[root@liumiaocn goprj]#
执行结果
[root@liumiaocn goprj]# go run basic-buildin2.go
a1= &[0 0 0 0 5 0 0 8 0 0] len(a1)= 10 cap(a1)= 10
before copy :s1= [5 0 0 0 2] len(s1)= 5 cap(s1)= 10
before copy :s2= [1 0 0 0 3] len(s2)= 5 cap(s2)= 10
copy(s2,s1)
after copy :s1= [5 0 0 0 2] len(s1)= 5 cap(s1)= 10
after copy :s2= [5 0 0 0 2] len(s2)= 5 cap(s2)= 10
reset
after reset:s1= [5 0 0 0 2] len(s1)= 5 cap(s1)= 10
after reset :s2= [1 0 0 0 3] len(s2)= 5 cap(s2)= 10
append(s2,20)
after append:s1= [5 0 0 0 2] len(s1)= 5 cap(s1)= 10
after append:s2= [1 0 0 0 3 6] len(s2)= 6 cap(s2)= 10
after append:s2= [1 0 0 0 3 6 7 8 9 10] len(s2)= 10 cap(s2)= 10
after append:s2= [1 0 0 0 3 6 7 8 9 10 11] len(s2)= 11 cap(s2)= 20
[root@liumiaocn goprj]#
复数操作
例子代码
[root@liumiaocn goprj]# cat basic-buildin3.go
package main
import "fmt"
func main() {
var c1 = complex(1.1, 2)
var r1 = real(c1)
var i1 = imag(c1)
println("c1=", c1, " r1=", r1, " i1=", i1)
fmt.Println("c1=", c1, " r1=", r1, " i1=", i1)
}
[root@liumiaocn goprj]#
执行结果
[root@liumiaocn goprj]
c1= (+1.100000e+000+2.000000e+000i) r1= +1.100000e+000 i1= +2.000000e+000
c1= (1.1+2i) r1= 1.1 i1= 2
[root@liumiaocn goprj]
