Golang Basic 2 - Basic Data Types && Variable

Basic Data Types

• int, eg. 0, 1, 2, 3.
• float32, float64, eg. 3.14159.
• string, eg. "Hello World".
• bool, eg. true, false.
• rune, eg. 'a', 'b'. (char, saved as int)

Variable

Declear variable

var VariableName DataType

Set value

VariableName = Value

Sample

usr@host:go/ # cat l2s1.go
package main
import (
    "fmt"
)
func main(){
    // declear variables
    var int_val int         // declear an int variable
    var float_val float64   // declear a float variable
    var string_val string   // declear a string variable
    var bool_val bool       // declear a bool variable
    var rune_val rune       // declear a rune variable
    // set value for variables
    int_val = 3
    float_val = 1.234
    string_val = "Hello"
    bool_val = true
    rune_val = 'A'
    // print them
    fmt.Println(int_val)
    fmt.Println(float_val)
    fmt.Println(string_val)
    fmt.Println(bool_val)
    fmt.Println(rune_val)
}
usr@host:go/ # go build l2s1.go
usr@host:go/ # ./l2s1
3
1.234
Hello
true
65

Declear && Set value at the same time

    var VariableName DataType = Value

Sample

usr@host:go/ # cat l2s2.go
package main
import (
    "fmt"
)
func main(){
    // declear and set variables
    var int_val int = 3
    var float_val float64 = 1.234
    var string_val string = "Hello"
    var bool_val bool = true
    var rune_val rune = 'A'
    // print them
    fmt.Println(int_val)
    fmt.Println(float_val)
    fmt.Println(string_val)
    fmt.Println(bool_val)
    fmt.Println(rune_val)
}
usr@host:go/ # go build l2s2.go
usr@host:go/ # ./l2s2
3
1.234
Hello
true
65

Change values in variable

usr@host:go/ # cat l2s3.go
package main
import (
    "fmt"
)
func main(){
    // declear and set variable
    var int_val int = 3
    // print them
    fmt.Println(int_val)
    // set new value for variable
    int_val = 5
    // print them
    fmt.Println(int_val)
}
usr@host:go/ # go build l2s3.go
usr@host:go/ # ./l2s3
3
5

Some errors

usr@host:go/ # cat l2s4.go
package main
import (
    "fmt"
)
func main(){
    // declear and set variable
    var int_val int = 3
    // print them
    fmt.Println(int_val)
    // set new value for variable
    int_val = "abc"
    // print them
    fmt.Println(int_val)
}
usr@host:go/ # go build l2s4.go
# command-line-arguments
./l2s4.go:15:15: cannot use "abc" (type string) as type int in assignment

• The values we set for the variable must match the data type.