Conditional - If Statement

If Statements

bool
- true
- false
the not operator
- !
initialization statement
if/else
if/else
if/else
if/else if/.../else

If statements are conditional statements. Remember in control flow, we have sequence, we have iterative, and we also have conditional. Sequence is top to bottom, iterative is looping, and conditional is based upon a condition it will either do one thing or another.

Let's start with some predeclared constants, true and false and not true !true and not false !false

package main

import (
    "fmt"
)

func main() {
    if true {
        fmt.Println("001")
    }

    if false {
        fmt.Println("002")
    }

    if !true {
        fmt.Println("003")
    }

    if !false {
        fmt.Println("004")
    }
}

playground

Following through the example above, we see if true which will always be true, and will execute. if false will always be false, and will not execute. if !true is if not true, which is the same as false, and will not execute, while if !false is if not false, which will execute.

Let's try with some more examples using numbers and the not operator !:

package main

import (
    "fmt"
)

func main() {
    if 2 == 2 {
        fmt.Println("001")
    }

    if 2 != 2 {
        fmt.Println("002")
    }

    if !(2 == 2) {
        fmt.Println("003")
    }

    if !(2 != 2) {
        fmt.Println("004")
    }
}

playground

In Go, we mostly don't see semicolons at the end of statements in source. Though we do see them in initialization statments.

So, if we want to have two statements on one line, we can use a semicolon.

package main

import (
    "fmt"
)

func main() {
    fmt.Println("here's a statement"); fmt.Println("something else")
}

If you run format, the formatter will put this over two lines.

One usecase would be initialization of a variable and evaluation, for example if x := 42; x == 2 will initialize the variable x with the value of 42 then will evaluation the expression x == 2 which is false

package main

import (
    "fmt"
)

func main() {
    if x := 42; x == 2 {
        fmt.Println("001")
    }
    fmt.Println("here's a statement")
    fmt.Println("something else")
}