Regular updates

[twpd/master.git] / go.md

diff --git a/go.md b/go.md
index c88b508..1ca0142 100644 (file)
--- a/go.md
+++ b/go.md
@@ -5,12 +5,19 @@ prism_languages: [go, bash]
 weight: -3
 tags: [Featured]
 category: C-like
-updated: 2017-09-15
+updated: 2020-06-21
 ---
 
 ## Getting started
 {: .-three-column}
 
+### Introduction
+{: .-intro}
+
+- [A tour of Go](https://tour.golang.org/welcome/1) _(tour.golang.org)_
+- [Go repl](https://repl.it/languages/go) _(repl.it)_
+- [Golang wiki](https://github.com/golang/go/wiki/) _(github.com)_
+
 ### Hello world
 {: .-prime}
 
@@ -177,13 +184,13 @@ See: [If](https://tour.golang.org/flowcontrol/5)
 ### Statements in if
 
 ```go
-if _, err := getResult(); err != nil {
+if _, err := doThing(); err != nil {
   fmt.Println("Uh oh")
 }
 ```
 {: data-line="1"}
 
-A condition in an `if` statement can be preceded with a statement before a `;`.
+A condition in an `if` statement can be preceded with a statement before a `;`. Variables declared by the statement are only in scope until the end of the `if`.
 
 See: [If with a short statement](https://tour.golang.org/flowcontrol/6)
 
@@ -226,6 +233,18 @@ for i, val := range entry {
 
 See: [For-Range loops](https://gobyexample.com/range)
 
+### While loop
+
+```go
+n := 0
+x := 42
+for n != x {
+  n := guess()
+}
+```
+
+See: [Go's "while"](https://tour.golang.org/flowcontrol/3)
+
 ## Functions
 {: .-three-column}
 
@@ -412,7 +431,7 @@ func main() {
   for _, item := range itemList {
     // Increment WaitGroup Counter
     wg.Add(1)
-    go doOperation(item)
+    go doOperation(&wg, item)
   }
   // Wait for goroutines to finish
   wg.Wait()
@@ -422,7 +441,7 @@ func main() {
 {: data-line="1,4,8,12"}
 
 ```go
-func doOperation(item string) {
+func doOperation(wg *sync.WaitGroup, item string) {
   defer wg.Done()
   // do operation on item
   // ...
@@ -461,7 +480,6 @@ func main() {
   fmt.Println("Working...")
 }
 ```
-
 {: data-line="2,3,4"}
 
 Lambdas are better suited for defer blocks.
@@ -547,7 +565,7 @@ func (v Vertex) Abs() float64 {
 {: data-line="1"}
 
 ```go
-v: = Vertex{1, 2}
+v := Vertex{1, 2}
 v.Abs()
 ```
 
@@ -575,12 +593,63 @@ By defining your receiver as a pointer (`*Vertex`), you can do mutations.
 
 See: [Pointer receivers](https://tour.golang.org/methods/4)
 
+## Interfaces
+
+### A basic interface
+
+```go
+type Shape interface {
+  Area() float64
+  Perimeter() float64
+}
+```
+
+### Struct
+
+```go
+type Rectangle struct {
+  Length, Width float64
+}
+```
+
+Struct `Rectangle` implicitly implements interface `Shape` by implementing all of its methods.
+
+### Methods
+
+```go
+func (r Rectangle) Area() float64 {
+  return r.Length * r.Width
+}
+
+func (r Rectangle) Perimeter() float64 {
+  return 2 * (r.Length + r.Width)
+}
+```
+
+The methods defined in `Shape` are implemented in `Rectangle`.
+
+### Interface example
+
+```go
+func main() {
+  var r Shape = Rectangle{Length: 3, Width: 4}
+  fmt.Printf("Type of r: %T, Area: %v, Perimeter: %v.", r, r.Area(), r.Perimeter())
+}
+```
+
 ## References
 
+### Official resources
+{: .-intro}
+
 - [A tour of Go](https://tour.golang.org/welcome/1) _(tour.golang.org)_
 - [Golang wiki](https://github.com/golang/go/wiki/) _(github.com)_
-- [Awesome Go](https://awesome-go.com/) _(awesome-go.com)_
-- [Go by Example](https://gobyexample.com/) _(gobyexample.com)_
 - [Effective Go](https://golang.org/doc/effective_go.html) _(golang.org)_
+
+### Other links
+{: .-intro}
+
+- [Go by Example](https://gobyexample.com/) _(gobyexample.com)_
+- [Awesome Go](https://awesome-go.com/) _(awesome-go.com)_
 - [JustForFunc Youtube](https://www.youtube.com/channel/UC_BzFbxG2za3bp5NRRRXJSw) _(youtube.com)_
 - [Style Guide](https://github.com/golang/go/wiki/CodeReviewComments) _(github.com)_