Archive for the ‘Go’ Category

EXPORTED NAMES

 

After importing a package, you can refer to the names it exports.

In Go, a name is exported if it begins with a capital letter.

Foo is an exported name, as is FOO. The name foo is not exported.

Run the code. Then rename math.pi to math.Pi and try it again.

Example :

package main

import (
“fmt”
“math”
)

func main() {
fmt.Println(math.pi)
}

output:

prog.go:9: cannot refer to unexported name math.pi
prog.go:9: undefined: math.pi

after renaming math.pi to math.Pi

package main

import (
“fmt”
“math”
)

func main() {
fmt.Println(math.Pi)
}

output:

3.141592653589793
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IMPORTS

 

This code groups the imports into a parenthesized, “factored” import statement. You can also write multiple import statements, like:

	import "fmt"
	import "math"

but it’s common to use the factored form to eliminate clutter.

Example :

package main

import (
“fmt”
“math”
)

func main() {
fmt.Printf(“Now you have %g problems.”,
math.Nextafter(2, 3))
}

output:

Now you have 2.0000000000000004 problems.

PACKAGES

 

Every Go program is made up of packages.

Programs start running in package main.

This program is using the packages with import paths "fmt" and"math".

By convention, the package name is the same as the last element of the import path.

Example:

package main

import (
“fmt”
“math”
)

func main() {
fmt.Println(“Happy”, math.Pi, “Day”)
}

output :

Happy 3.141592653589793 Day

This tour is also available as a stand-alone program that you can use without access to the internet.

The stand-alone tour is faster, as it builds and runs the code samples on your own machine. It also includes additional exercises not available in this sandboxed version.

To run the tour locally first install Go, then use go get to install gotour:

    go get code.google.com/p/go-tour/gotour

and run the resultant gotour executable.

Welcome to a tour of the Go programming language.

The tour is divided into three sections. At the end of each section is a series of exercises for you to complete.

The tour is interactive. Click the Run button now (or type Shift-Enter) to compile and run the program on a remote server. The result is displayed below the code.

These example programs demonstrate different aspects of Go. The programs in the tour are meant to be starting points for your own experimentation.

Edit the program and run it again.

Whenever you’re ready to move on, click the Next button or type the PageDown key.

Example:

package main

import “fmt”

func main() {
fmt.Println(“Hello, 世界”)
}

output :

Hello, 世界