7. Toad Notes Go language--if,switch,defer

This is a creation in Article, where the information may have evolved or changed.

7. Toad Notes Go language--if,switch,defer

If

The IF statements do not appear to be the same as in C or Java, except that they do not have ' () ' (even forcing them to be used), and ' {} ' is required.

Package Main

Import (

"FMT"

"Math"

)

Func sqrt (x float64) string {

If x< 0 {

RETURNSQRT (-X) + "I"

}

Returnfmt. Sprint (Math. SQRT (x))

}

Func Main () {

Fmt. Println (sqrt (2), sqrt (-4))

}

Perform:

1.4142135623730951 2i

As with for, the ' if ' statement can execute a simple statement before the condition.

The scope of the variable defined by this statement is only within the IF range.

(Use V at the last return statement.) ）

Package Main

Import (

"FMT"

"Math"

)

Func pow (x, N, Lim float64) float64 {

If V: =math. Pow (x, N); V < Lim {

Returnv

}

Returnlim

}

Func Main () {

Fmt. Println (

Pow (3,2, 10),

Pow (3,3, 20),

)

}

The results of the implementation are as follows:

920

Variables defined in the handy statement of if can also be used in any corresponding else block.

Package Main

Import (

"FMT"

"Math"

)

Func pow (x, N, Lim float64) float64 {

If V: =math. Pow (x, N); V < Lim {

Returnv

} else{

Fmt. Printf ("%g>=%g\n", V, Lim)

}

         // You can't use it at the beginning. v the

Returnlim

}

Func Main () {

Fmt. Println (

Pow (3,2, 10),

Pow (3,3, 20),

)

}

Execution Result:

27>= 20

920

Switch

A struct (' struct ') is a collection of fields.

The branch terminates automatically unless the Fallthrough statement ends.

Perform:

Package Main

Import (

"FMT"

"Runtime"

)

Func Main () {

Fmt. Print ("Goruns on")

Switchos: = runtime. GOOS; OS {

Case "Darwin":

Fmt. Println ("OSX.")

Case "Linux":

Fmt. Println ("Linux.")

Default

FreeBSD, OpenBSD,

Plan9, Windows ...

Fmt. Printf ("%s.", OS)

}

}

Results:

Goruns on Windows.

The order in which switch is executed

The switch condition is executed from top to bottom and stops when the match succeeds.

For example

Switch I {

Case 0:

Case F ():

}

' F ' is not called when i==0. ）

Code:

Package Main

Import (

"FMT"

"Time"

)

Func Main () {

Fmt. Println ("When ' Ssaturday?")

today:= time. Now (). Weekday ()

Switchtime. Saturday {

Casetoday + 0:

Fmt. Println ("Today.")

Casetoday + 1:

Fmt. Println ("Tomorrow.")

Casetoday + 2:

Fmt. Println ("Intwo days.")

Default

Fmt. Println ("Toofar away.")

}

}

Perform:

When ' Ssaturday?

Toofar away.

Switch with no conditions

A switch with no conditions is the same as ' switch true '.

This structure allows the long if-then-else chain to be written in a clearer form.

Package Main

Import (

"FMT"

"Time"

)

Func Main () {

T: =time. Now ()

switch{

Caset. Hour () < 12:

Fmt. Println ("goodmorning!")

Caset. Hour () < 17:

Fmt. Println ("Goodafternoon.")

Default

Fmt. Println ("goodevening.")

}

}

Perform:

Goodevening.

Defer

The defer statement delays the execution of the function until the upper function returns.

The parameters of the deferred call are generated immediately, but the function is not called before the upper function returns.

Code:

Package Main

Import "FMT"

Func Main () {

Deferfmt. PRINTLN ("World")

Fmt. Println ("Hello")

}

EXECUTE as follows:

Hello

World

Defer stack

The deferred function call is pressed into a stack. When the function returns, the deferred function call is called in the order of last in, first out.

Code:

Package Main

Import "FMT"

Func Main () {

Fmt. Println ("Counting")

For i:= 0; I < 10; i++ {

Deferfmt. Println (i)

}

Fmt. Println ("Done")

}

Perform:

Counting

Done

9

8

7

6

5

4

3

2

1

0