wip/go: add

wip/go.md

@@ -0,0 +1,396 @@
+---
+title: Go
+layout: 2017/sheet
+prism_languages: [go, bash]
+tags: [WIP]
+---
+
+## Getting started
+{: .-three-column}
+
+### Hello world
+{: .-prime}
+
+```go
+// hello.go
+package main
+
+import ( "fmt" )
+
+func main() {
+  message := greetMe("world")
+  fmt.Println(message)
+}
+
+func greetMe(name string) (string) {
+  return "Hello, " + name + "!"
+}
+```
+
+```bash
+$ go build
+```
+
+Or try it out in the [Go repl](https://repl.it/languages/go), or [A Tour of Go](https://tour.golang.org/welcome/1).
+
+### Variables
+
+```go
+// Variable declaration
+var msg string
+msg = "Hello"
+```
+
+```go
+// Shortcut of above (Infers type)
+msg := "Hello"
+```
+
+### Constants
+
+```go
+const Phi = 1.618
+```
+
+Constants can be character, string, boolean, or numeric values.
+
+See: [Constants](https://tour.golang.org/basics/15)
+
+## Basic types
+{: .-three-column}
+
+### Strings
+
+```go
+str := "Hello"
+```
+
+```go
+str := `Multiline
+string`
+```
+
+Strings are of type `string`.
+
+### Numbers
+
+```go
+// Typical types:
+num := 3          // int
+num := 3.         // float64
+num := 3 + 4i     // complex128
+num :+ byte('a')  // byte (alias for uint8)
+```
+
+```go
+// Other types:
+var u uint = 7        // uint (unsigned)
+var p float32 = 22.7  // 32-bit float
+```
+
+### Arrays
+
+```go
+// var numbers [5]int
+numbers := [...]int{0, 0, 0, 0, 0}
+```
+
+Arrays have a fixed size.
+
+### Slices
+
+```go
+slice := []int{2, 3, 4}
+```
+
+```go
+slice := []byte("Hello")
+```
+
+Slices have a dynamic size, unlike arrays.
+
+### Pointers
+
+```go
+func main () {
+  b := *getPointer()
+  fmt.Println("Value is", b)
+}
+```
+{: data-line="2"}
+
+```go
+func getPointer () (myPointer *int) {
+  a := 234
+  return &a
+}
+```
+{: data-line="3"}
+
+Pointers point to a memory location of a variable. Go is fully garbage-collected.
+
+See: [Pointers](https://tour.golang.org/moretypes/1)
+
+### Type conversions
+
+```go
+i := 2
+f := float64(i)
+u := uint(i)
+```
+
+See: [Type conversions](https://tour.golang.org/basics/13)
+
+## Flow control
+{: .-three-column}
+
+### Conditional
+
+```go
+if day == "sunday" || day == "saturday" {
+  rest()
+} else if day == "monday" && isTired() {
+  groan()
+} else {
+  work()
+}
+```
+{: data-line="1,3,5"}
+
+See: [If](https://tour.golang.org/flowcontrol/5)
+
+### Statements in if
+
+```go
+if _, err := getResult(); err != nil {
+  fmt.Println("Uh oh")
+}
+```
+{: data-line="1"}
+
+A condition in an `if` statement can be preceeded with a statement before a `;`.
+
+See: [If with a short statement](https://tour.golang.org/flowcontrol/6)
+
+### Switch
+
+```go
+switch day {
+  case "sunday":
+    // cases don't "fall through" by default!
+    fallthrough
+
+  case "saturday":
+    rest()
+
+  default:
+    work()
+}
+```
+
+See: [Switch](https://github.com/golang/go/wiki/Switch)
+
+## Functions
+{: .-three-column}
+
+### Lambdas
+
+```go
+myfunc := func() bool {
+  return x > 10000
+}
+```
+{: data-line="1"}
+
+Functions are first class objects.
+
+### Multiple return types
+
+```go
+a, b := getMessage()
+```
+
+```go
+func getMessage() (a string, b string) {
+  return "Hello", "World"
+}
+```
+{: data-line="2"}
+
+
+### Named return values
+
+```go
+func split(sum int) (x, y int) {
+  x := sum * 4 / 9
+  y := sum - x
+  return
+}
+```
+{: data-line="4"}
+
+By defining the return value names in the signature, a `return` (no args) will return variables with those names.
+
+See: [Named return values](https://tour.golang.org/basics/7)
+
+## Concurrency
+{: .-three-column}
+
+### Goroutines
+
+```go
+func main() {
+  // A "channel"
+  ch := make(chan string)
+
+  // Start concurrent routines
+  go push("Moe", ch)
+  go push("Larry", ch)
+  go push("Curly", ch)
+
+  // Read 3 results
+  // (Since our goroutines are concurrent,
+  // the order isn't guaranteed!)
+  fmt.Println(<-ch, <-ch, <-ch)
+}
+```
+{: data-line="3,6,7,8,13"}
+
+```go
+func push(name string, ch chan string) {
+  msg := "Hey, " + name
+  ch <- msg
+}
+```
+{: data-line="3"}
+
+Channels are concurrency-safe communication objects, used in goroutines.
+
+See: [Goroutines](https://tour.golang.org/concurrency/1), [Channels](https://tour.golang.org/concurrency/2)
+
+### Buffered channels
+
+```go
+ch := make(chan int, 2)
+ch <- 1
+ch <- 2
+ch <- 3
+// fatal error:
+// all goroutines are asleep - deadlock!
+```
+{: data-line="1"}
+
+Buffered channels limit the amount of messages it can keep.
+
+See: [Buffered channels](https://tour.golang.org/concurrency/3)
+
+### Closing channels
+
+```go
+// Closes a channel
+ch <- 1
+ch <- 2
+ch <- 3
+close(ch)
+```
+{: data-line="5"}
+
+```go
+// Iterates across a channel until its closed
+for i := range ch {
+  ···
+}
+```
+
+```go
+// Closed if ok == false
+v, ok := <- ch
+```
+
+See: [Range and close](https://tour.golang.org/concurrency/4)
+
+## Error control
+
+### Defer
+
+```go
+func main() {
+  defer fmt.Println("Done")
+  fmt.Println("Working...")
+}
+```
+{: data-line="2"}
+
+Defers running a function until the surrounding function returns.
+The arguments are evaluated immediately, but the function call is not ran until later.
+
+See: [Defer, panic and recover](https://blog.golang.org/defer-panic-and-recover)
+
+### Deferring functions
+
+```go
+func main() {
+  defer func() {
+    fmt.Println("Done")
+  }
+  fmt.Println("Working...")
+}
+```
+{: data-line="2,3,4"}
+
+Lambdas are better suited for defer blocks.
+
+## Structs
+{: .-three-column}
+
+### Defining
+
+```go
+type Vertex struct {
+  X int
+  Y int
+}
+```
+{: data-line="1,2,3,4"}
+
+```go
+func main() {
+  v := Vertex{1, 2}
+  v.X = 4
+  fmt.Println(v.X, v.Y)
+}
+```
+
+See: [Structs](https://tour.golang.org/moretypes/2)
+
+### Literals
+
+```go
+v := Vertex{X: 1, Y: 2}
+```
+
+```go
+// Field names can be omitted
+v := Vertex{1, 2}
+```
+
+```go
+// Y is implicit
+v := Vertex{X: 1}
+```
+
+You can also put field names.
+
+### Pointers to structs
+
+```go
+v := &Vertex{1, 2}
+v.X = 2
+```
+
+Doing `v.X` is the same as doing `(*v).X`, when `v` is a pointer.
+
+## References
+
+- [A tour of Go](https://tour.golang.org/welcome/1) _(tour.golang.org)_
+- [Golang wiki](https://github.com/golang/go/wiki/) _(github.com)_