summaryrefslogtreecommitdiffhomepage
diff options
context:
space:
mode:
-rw-r--r--go.html.markdown146
1 files changed, 75 insertions, 71 deletions
diff --git a/go.html.markdown b/go.html.markdown
index d68ba51b..d1a0ae34 100644
--- a/go.html.markdown
+++ b/go.html.markdown
@@ -6,6 +6,7 @@ filename: learngo.go
contributors:
- ["Sonia Keys", "https://github.com/soniakeys"]
- ["Christopher Bess", "https://github.com/cbess"]
+ - ["Jesse Johnson", "https://github.com/holocronweaver"]
---
Go was created out of the need to get work done. It's not the latest trend
@@ -30,9 +31,10 @@ package main
// Import declaration declares library packages referenced in this file.
import (
- "fmt" // A package in the Go standard library
+ "fmt" // A package in the Go standard library.
"net/http" // Yes, a web server!
- "strconv" // String conversions
+ "strconv" // String conversions.
+ m "math" // Math library with local alias m.
)
// A function definition. Main is special. It is the entry point for the
@@ -53,49 +55,49 @@ func beyondHello() {
x = 3 // Variable assignment.
// "Short" declarations use := to infer the type, declare, and assign.
y := 4
- sum, prod := learnMultiple(x, y) // function returns two values
- fmt.Println("sum:", sum, "prod:", prod) // simple output
+ sum, prod := learnMultiple(x, y) // Function returns two values.
+ fmt.Println("sum:", sum, "prod:", prod) // Simple output.
learnTypes() // < y minutes, learn more!
}
// Functions can have parameters and (multiple!) return values.
func learnMultiple(x, y int) (sum, prod int) {
- return x + y, x * y // return two values
+ return x + y, x * y // Return two values.
}
// Some built-in types and literals.
func learnTypes() {
// Short declaration usually gives you what you want.
- s := "Learn Go!" // string type
+ s := "Learn Go!" // string type.
s2 := `A "raw" string literal
-can include line breaks.` // same string type
+can include line breaks.` // Same string type.
- // non-ASCII literal. Go source is UTF-8.
- g := 'Σ' // rune type, an alias for uint32, holds a unicode code point
+ // Non-ASCII literal. Go source is UTF-8.
+ g := 'Σ' // rune type, an alias for uint32, holds a unicode code point.
- f := 3.14195 // float64, an IEEE-754 64-bit floating point number
- c := 3 + 4i // complex128, represented internally with two float64s
+ f := 3.14195 // float64, an IEEE-754 64-bit floating point number.
+ c := 3 + 4i // complex128, represented internally with two float64's.
// Var syntax with an initializers.
- var u uint = 7 // unsigned, but implementation dependent size as with int
+ var u uint = 7 // Unsigned, but implementation dependent size as with int.
var pi float32 = 22. / 7
// Conversion syntax with a short declaration.
- n := byte('\n') // byte is an alias for uint8
+ n := byte('\n') // byte is an alias for uint8.
// Arrays have size fixed at compile time.
- var a4 [4]int // an array of 4 ints, initialized to all 0
- a3 := [...]int{3, 1, 5} // an array of 3 ints, initialized as shown
+ var a4 [4]int // An array of 4 ints, initialized to all 0.
+ a3 := [...]int{3, 1, 5} // An array of 3 ints, initialized as shown.
// Slices have dynamic size. Arrays and slices each have advantages
// but use cases for slices are much more common.
- s3 := []int{4, 5, 9} // compare to a3. no ellipsis here
- s4 := make([]int, 4) // allocates slice of 4 ints, initialized to all 0
- var d2 [][]float64 // declaration only, nothing allocated here
- bs := []byte("a slice") // type conversion syntax
+ s3 := []int{4, 5, 9} // Compare to a3. No ellipsis here.
+ s4 := make([]int, 4) // Allocates slice of 4 ints, initialized to all 0.
+ var d2 [][]float64 // Declaration only, nothing allocated here.
+ bs := []byte("a slice") // Type conversion syntax.
- p, q := learnMemory() // declares p, q to be type pointer to int.
+ p, q := learnMemory() // Declares p, q to be type pointer to int.
fmt.Println(*p, *q) // * follows a pointer. This prints two ints.
// Maps are a dynamically growable associative array type, like the
@@ -109,23 +111,23 @@ can include line breaks.` // same string type
// Output of course counts as using a variable.
fmt.Println(s, c, a4, s3, d2, m)
- learnFlowControl() // back in the flow
+ learnFlowControl() // Back in the flow.
}
// Go is fully garbage collected. It has pointers but no pointer arithmetic.
// You can make a mistake with a nil pointer, but not by incrementing a pointer.
func learnMemory() (p, q *int) {
// Named return values p and q have type pointer to int.
- p = new(int) // built-in function new allocates memory.
+ p = new(int) // Built-in function new allocates memory.
// The allocated int is initialized to 0, p is no longer nil.
- s := make([]int, 20) // allocate 20 ints as a single block of memory
- s[3] = 7 // assign one of them
- r := -2 // declare another local variable
+ s := make([]int, 20) // Allocate 20 ints as a single block of memory.
+ s[3] = 7 // Assign one of them.
+ r := -2 // Declare another local variable.
return &s[3], &r // & takes the address of an object.
}
-func expensiveComputation() int {
- return 1e6
+func expensiveComputation() float64 {
+ return m.Exp(10)
}
func learnFlowControl() {
@@ -135,29 +137,31 @@ func learnFlowControl() {
}
// Formatting is standardized by the command line command "go fmt."
if false {
- // pout
+ // Pout.
} else {
- // gloat
+ // Gloat.
}
// Use switch in preference to chained if statements.
- x := 1
+ x := 42.0
switch x {
case 0:
case 1:
- // cases don't "fall through"
- case 2:
- // unreached
+ case 42:
+ // Cases don't "fall through".
+ case 43:
+ // Unreached.
}
// Like if, for doesn't use parens either.
- for x := 0; x < 3; x++ { // ++ is a statement
+ // Variables declared in for and if are local to their scope.
+ for x := 0; x < 3; x++ { // ++ is a statement.
fmt.Println("iteration", x)
}
- // x == 1 here.
+ // x == 42 here.
// For is the only loop statement in Go, but it has alternate forms.
- for { // infinite loop
- break // just kidding
- continue // unreached
+ for { // Infinite loop.
+ break // Just kidding.
+ continue // Unreached.
}
// As with for, := in an if statement means to declare and assign y first,
// then test y > x.
@@ -166,30 +170,17 @@ func learnFlowControl() {
}
// Function literals are closures.
xBig := func() bool {
- return x > 100 // references x declared above switch statement.
+ return x > 100 // References x declared above switch statement.
}
- fmt.Println("xBig:", xBig()) // true (we last assigned 1e6 to x)
- x /= 1e5 // this makes it == 10
- fmt.Println("xBig:", xBig()) // false now
+ fmt.Println("xBig:", xBig()) // true (we last assigned 1e6 to x).
+ x /= m.Exp(9) // This makes x == e.
+ fmt.Println("xBig:", xBig()) // false now.
// When you need it, you'll love it.
goto love
love:
- // Good stuff coming up!
- learnVariadicParams("great", "learning", "here!")
- learnInterfaces()
-}
-
-// Functions can have variadic parameters
-func learnVariadicParams(myStrings ...string) {
- // iterate each value of the variadic
- for _, param := range myStrings {
- fmt.Println("param:", param)
- }
-
- // pass variadic value as a variadic parameter
- fmt.Println("params:", fmt.Sprintln(myStrings...))
+ learnInterfaces() // Good stuff coming up!
}
// Define Stringer as an interface type with one method, String.
@@ -213,16 +204,29 @@ func learnInterfaces() {
// Brace syntax is a "struct literal." It evaluates to an initialized
// struct. The := syntax declares and initializes p to this struct.
p := pair{3, 4}
- fmt.Println(p.String()) // call String method of p, of type pair.
- var i Stringer // declare i of interface type Stringer.
- i = p // valid because pair implements Stringer
+ fmt.Println(p.String()) // Call String method of p, of type pair.
+ var i Stringer // Declare i of interface type Stringer.
+ i = p // Valid because pair implements Stringer
// Call String method of i, of type Stringer. Output same as above.
fmt.Println(i.String())
// Functions in the fmt package call the String method to ask an object
// for a printable representation of itself.
- fmt.Println(p) // output same as above. Println calls String method.
- fmt.Println(i) // output same as above
+ fmt.Println(p) // Output same as above. Println calls String method.
+ fmt.Println(i) // Output same as above.
+
+ learnVariadicParams("great", "learning", "here!")
+}
+
+// Functions can have variadic parameters.
+func learnVariadicParams(myStrings ...interface{}) {
+ // Iterate each value of the variadic.
+ for _, param := range myStrings {
+ fmt.Println("param:", param)
+ }
+
+ // Pass variadic value as a variadic parameter.
+ fmt.Println("params:", fmt.Sprintln(myStrings...))
learnErrorHandling()
}
@@ -237,7 +241,7 @@ func learnErrorHandling() {
}
// An error value communicates not just "ok" but more about the problem.
if _, err := strconv.Atoi("non-int"); err != nil { // _ discards value
- // prints "strconv.ParseInt: parsing "non-int": invalid syntax"
+ // prints 'strconv.ParseInt: parsing "non-int": invalid syntax'
fmt.Println(err)
}
// We'll revisit interfaces a little later. Meanwhile,
@@ -264,19 +268,19 @@ func learnConcurrency() {
// There is no telling in what order the results will arrive!
fmt.Println(<-c, <-c, <-c) // channel on right, <- is "receive" operator.
- cs := make(chan string) // another channel, this one handles strings.
- cc := make(chan chan string) // a channel of string channels.
- go func() { c <- 84 }() // start a new goroutine just to send a value
- go func() { cs <- "wordy" }() // again, for cs this time
+ cs := make(chan string) // Another channel, this one handles strings.
+ ccs := make(chan chan string) // A channel of string channels.
+ go func() { c <- 84 }() // Start a new goroutine just to send a value.
+ go func() { cs <- "wordy" }() // Again, for cs this time.
// Select has syntax like a switch statement but each case involves
// a channel operation. It selects a case at random out of the cases
// that are ready to communicate.
select {
- case i := <-c: // the value received can be assigned to a variable
+ case i := <-c: // The value received can be assigned to a variable,
fmt.Printf("it's a %T", i)
- case <-cs: // or the value received can be discarded
+ case <-cs: // or the value received can be discarded.
fmt.Println("it's a string")
- case <-cc: // empty channel, not ready for communication.
+ case <-ccs: // Empty channel, not ready for communication.
fmt.Println("didn't happen.")
}
// At this point a value was taken from either c or cs. One of the two
@@ -287,7 +291,7 @@ func learnConcurrency() {
// A single function from package http starts a web server.
func learnWebProgramming() {
- // ListenAndServe first parameter is TCP address to listen at.
+ // First parameter of ListenAndServe is TCP address to listen to.
// Second parameter is an interface, specifically http.Handler.
err := http.ListenAndServe(":8080", pair{})
fmt.Println(err) // don't ignore errors
@@ -295,7 +299,7 @@ func learnWebProgramming() {
// Make pair an http.Handler by implementing its only method, ServeHTTP.
func (p pair) ServeHTTP(w http.ResponseWriter, r *http.Request) {
- // Serve data with a method of http.ResponseWriter
+ // Serve data with a method of http.ResponseWriter.
w.Write([]byte("You learned Go in Y minutes!"))
}
```