01 - fmt-y Dumpty

Covered in this module:

hello world

Entry point to your application is a main function:

package main

import "fmt"

func main() {
    fmt.Println("hello world")
}

package main

import (
    "fmt"
    "math"
)

Library fmt, pronounced fumpt, provides many common utilities:

function	behavior
`Println`	print all provided parameters, newline is automatic
`Printf`	first parameter is a format string with placeholders followed by parameters to replace the placeholders. No auto newline
`Print`	print all provided parameters

function	behavior
`%v`	default format (uses the default for types as below)
`%d`	for int, base 10 value
`%s`	uninterpreted bytes of string
`%t`	for bool, the word true or false

Returns a string built from the formatting string (first parameter) and a list of operands to replace verbs (e.g. %v).

fmt.Sprintf("They're waiting for you %v… in the test chamber.", "Gordon")

Keyword var can be used to declare one or many variables

var name string

You can initialize the variable inline. Types are inferred.

var name = "Gophee"

Go provides the shorthand operator := to declare and initialize a variable

time := "a flat circle"

Declaring variables that are not initialized are automatically zero-valued

var (
    name string
    num int
    state bool
)

fmt.Printf("\"%v\" - %v: %v", name, num, state)

prints

"" - 0: false

Note

Primitives can not be nil, only pointers (pointers are covered in part 8).

will take a type implicitly when used as a parameter

const (
    a = 9000
    b = 4000
)
fmt.Println(math.Max(a, b))
// math.Max expects two float64 parameters