Translate Go-tutorial to Finnish

1 files changed, 428 insertions, 0 deletions

diff --git a/fi-fi/go-fi.html.markdown b/fi-fi/go-fi.html.markdown
new file mode 100644
index 00000000..dc684227
--- /dev/null
+++ b/fi-fi/go-fi.html.markdown
@@ -0,0 +1,428 @@
+---
+name: Go
+category: language
+language: Go
+filename: learngo.go
+contributors:
+    - ["Sonia Keys", "https://github.com/soniakeys"]
+    - ["Christopher Bess", "https://github.com/cbess"]
+    - ["Jesse Johnson", "https://github.com/holocronweaver"]
+    - ["Quint Guvernator", "https://github.com/qguv"]
+    - ["Jose Donizetti", "https://github.com/josedonizetti"]
+    - ["Alexej Friesen", "https://github.com/heyalexej"]
+    - ["Clayton Walker", "https://github.com/cwalk"]
+---
+
+Go was created out of the need to get work done. It's not the latest trend
+in computer science, but it is the newest fastest way to solve real-world
+problems.
+
+It has familiar concepts of imperative languages with static typing.
+It's fast to compile and fast to execute, it adds easy-to-understand
+concurrency to leverage today's multi-core CPUs, and has features to
+help with large-scale programming.
+
+Go comes with a great standard library and an enthusiastic community.
+
+```go
+// Single line comment
+/* Multi-
+ line comment */
+
+// A package clause starts every source file.
+// Main is a special name declaring an executable rather than a library.
+package main
+
+// Import declaration declares library packages referenced in this file.
+import (
+	"fmt"       // A package in the Go standard library.
+	"io/ioutil" // Implements some I/O utility functions.
+	m "math"    // Math library with local alias m.
+	"net/http"  // Yes, a web server!
+	"strconv"   // String conversions.
+)
+
+// A function definition. Main is special. It is the entry point for the
+// executable program. Love it or hate it, Go uses brace brackets.
+func main() {
+	// Println outputs a line to stdout.
+	// Qualify it with the package name, fmt.
+	fmt.Println("Hello world!")
+
+	// Call another function within this package.
+	beyondHello()
+}
+
+// Functions have parameters in parentheses.
+// If there are no parameters, empty parentheses are still required.
+func beyondHello() {
+	var x int // Variable declaration. Variables must be declared before use.
+	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.
+	learnTypes()                            // < y minutes, learn more!
+}
+
+/* <- multiline comment
+Functions can have parameters and (multiple!) return values.
+Here `x`, `y` are the arguments and `sum`, `prod` is the signature (what's returned).
+Note that `x` and `sum` receive the type `int`.
+*/
+func learnMultiple(x, y int) (sum, prod int) {
+	return x + y, x * y // Return two values.
+}
+
+// Some built-in types and literals.
+func learnTypes() {
+	// Short declaration usually gives you what you want.
+	str := "Learn Go!" // string type.
+
+	s2 := `A "raw" string literal
+can include line breaks.` // Same string type.
+
+	// Non-ASCII literal. Go source is UTF-8.
+	g := 'Σ' // rune type, an alias for int32, 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 float64's.
+
+	// var syntax with initializers.
+	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.
+
+	// 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 initialized with a fixed size of three
+	// elements, with values 3, 1, and 5.
+
+	// 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.
+
+	// Because they are dynamic, slices can be appended to on-demand.
+	// To append elements to a slice, the built-in append() function is used.
+	// First argument is a slice to which we are appending. Commonly,
+	// the array variable is updated in place, as in example below.
+	s := []int{1, 2, 3}		// Result is a slice of length 3.
+	s = append(s, 4, 5, 6)	// Added 3 elements. Slice now has length of 6.
+	fmt.Println(s) // Updated slice is now [1 2 3 4 5 6]
+
+	// To append another slice, instead of list of atomic elements we can
+	// pass a reference to a slice or a slice literal like this, with a
+	// trailing ellipsis, meaning take a slice and unpack its elements,
+	// appending them to slice s.
+	s = append(s, []int{7, 8, 9}...) // Second argument is a slice literal.
+	fmt.Println(s)	// Updated slice is now [1 2 3 4 5 6 7 8 9]
+
+	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
+	// hash or dictionary types of some other languages.
+	m := map[string]int{"three": 3, "four": 4}
+	m["one"] = 1
+
+	// Unused variables are an error in Go.
+	// The underscore lets you "use" a variable but discard its value.
+	_, _, _, _, _, _, _, _, _, _ = str, s2, g, f, u, pi, n, a3, s4, bs
+	// Output of course counts as using a variable.
+	fmt.Println(s, c, a4, s3, d2, m)
+
+	learnFlowControl() // Back in the flow.
+}
+
+// It is possible, unlike in many other languages for functions in go
+// to have named return values.
+// Assigning a name to the type being returned in the function declaration line
+// allows us to easily return from multiple points in a function as well as to
+// only use the return keyword, without anything further.
+func learnNamedReturns(x, y int) (z int) {
+	z = x * y
+	return // z is implicit here, because we named it earlier.
+}
+
+// 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.
+	// 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.
+	return &s[3], &r     // & takes the address of an object.
+}
+
+func expensiveComputation() float64 {
+	return m.Exp(10)
+}
+
+func learnFlowControl() {
+	// If statements require brace brackets, and do not require parentheses.
+	if true {
+		fmt.Println("told ya")
+	}
+	// Formatting is standardized by the command line command "go fmt."
+	if false {
+		// Pout.
+	} else {
+		// Gloat.
+	}
+	// Use switch in preference to chained if statements.
+	x := 42.0
+	switch x {
+	case 0:
+	case 1:
+	case 42:
+		// Cases don't "fall through".
+		/*
+		There is a `fallthrough` keyword however, see:
+		  https://github.com/golang/go/wiki/Switch#fall-through
+		*/
+	case 43:
+		// Unreached.
+	default:
+		// Default case is optional.
+	}
+	// Like if, for doesn't use parens either.
+	// 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 == 42 here.
+
+	// For is the only loop statement in Go, but it has alternate forms.
+	for { // Infinite loop.
+		break    // Just kidding.
+		continue // Unreached.
+	}
+
+	// You can use range to iterate over an array, a slice, a string, a map, or a channel.
+	// range returns one (channel) or two values (array, slice, string and map).
+	for key, value := range map[string]int{"one": 1, "two": 2, "three": 3} {
+		// for each pair in the map, print key and value
+		fmt.Printf("key=%s, value=%d\n", key, value)
+	}
+
+	// As with for, := in an if statement means to declare and assign
+	// y first, then test y > x.
+	if y := expensiveComputation(); y > x {
+		x = y
+	}
+	// Function literals are closures.
+	xBig := func() bool {
+		return x > 10000 // References x declared above switch statement.
+	}
+	fmt.Println("xBig:", xBig()) // true (we last assigned e^10 to x).
+	x = 1.3e3                    // This makes x == 1300
+	fmt.Println("xBig:", xBig()) // false now.
+
+	// What's more is function literals may be defined and called inline,
+	// acting as an argument to function, as long as:
+	// a) function literal is called immediately (),
+	// b) result type matches expected type of argument.
+	fmt.Println("Add + double two numbers: ",
+		func(a, b int) int {
+			return (a + b) * 2
+		}(10, 2)) // Called with args 10 and 2
+	// => Add + double two numbers: 24
+
+	// When you need it, you'll love it.
+	goto love
+love:
+
+	learnFunctionFactory() // func returning func is fun(3)(3)
+	learnDefer()      // A quick detour to an important keyword.
+	learnInterfaces() // Good stuff coming up!
+}
+
+func learnFunctionFactory() {
+	// Next two are equivalent, with second being more practical
+	fmt.Println(sentenceFactory("summer")("A beautiful", "day!"))
+
+	d := sentenceFactory("summer")
+	fmt.Println(d("A beautiful", "day!"))
+	fmt.Println(d("A lazy", "afternoon!"))
+}
+
+// Decorators are common in other languages. Same can be done in Go
+// with function literals that accept arguments.
+func sentenceFactory(mystring string) func(before, after string) string {
+	return func(before, after string) string {
+		return fmt.Sprintf("%s %s %s", before, mystring, after) // new string
+	}
+}
+
+func learnDefer() (ok bool) {
+	// Deferred statements are executed just before the function returns.
+	defer fmt.Println("deferred statements execute in reverse (LIFO) order.")
+	defer fmt.Println("\nThis line is being printed first because")
+	// Defer is commonly used to close a file, so the function closing the
+	// file stays close to the function opening the file.
+	return true
+}
+
+// Define Stringer as an interface type with one method, String.
+type Stringer interface {
+	String() string
+}
+
+// Define pair as a struct with two fields, ints named x and y.
+type pair struct {
+	x, y int
+}
+
+// Define a method on type pair. Pair now implements Stringer.
+func (p pair) String() string { // p is called the "receiver"
+	// Sprintf is another public function in package fmt.
+	// Dot syntax references fields of p.
+	return fmt.Sprintf("(%d, %d)", p.x, p.y)
+}
+
+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
+	// 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.
+
+	learnVariadicParams("great", "learning", "here!")
+}
+
+// Functions can have variadic parameters.
+func learnVariadicParams(myStrings ...interface{}) {
+	// Iterate each value of the variadic.
+	// The underbar here is ignoring the index argument of the array.
+	for _, param := range myStrings {
+		fmt.Println("param:", param)
+	}
+
+	// Pass variadic value as a variadic parameter.
+	fmt.Println("params:", fmt.Sprintln(myStrings...))
+
+	learnErrorHandling()
+}
+
+func learnErrorHandling() {
+	// ", ok" idiom used to tell if something worked or not.
+	m := map[int]string{3: "three", 4: "four"}
+	if x, ok := m[1]; !ok { // ok will be false because 1 is not in the map.
+		fmt.Println("no one there")
+	} else {
+		fmt.Print(x) // x would be the value, if it were in the map.
+	}
+	// 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'
+		fmt.Println(err)
+	}
+	// We'll revisit interfaces a little later. Meanwhile,
+	learnConcurrency()
+}
+
+// c is a channel, a concurrency-safe communication object.
+func inc(i int, c chan int) {
+	c <- i + 1 // <- is the "send" operator when a channel appears on the left.
+}
+
+// We'll use inc to increment some numbers concurrently.
+func learnConcurrency() {
+	// Same make function used earlier to make a slice. Make allocates and
+	// initializes slices, maps, and channels.
+	c := make(chan int)
+	// Start three concurrent goroutines. Numbers will be incremented
+	// concurrently, perhaps in parallel if the machine is capable and
+	// properly configured. All three send to the same channel.
+	go inc(0, c) // go is a statement that starts a new goroutine.
+	go inc(10, c)
+	go inc(-805, c)
+	// Read three results from the channel and print them out.
+	// 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.
+	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,
+		fmt.Printf("it's a %T", i)
+	case <-cs: // or the value received can be discarded.
+		fmt.Println("it's a string")
+	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
+	// goroutines started above has completed, the other will remain blocked.
+
+	learnWebProgramming() // Go does it. You want to do it too.
+}
+
+// A single function from package http starts a web server.
+func learnWebProgramming() {
+
+	// First parameter of ListenAndServe is TCP address to listen to.
+	// Second parameter is an interface, specifically http.Handler.
+	go func() {
+		err := http.ListenAndServe(":8080", pair{})
+		fmt.Println(err) // don't ignore errors
+	}()
+
+	requestServer()
+}
+
+// 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.
+	w.Write([]byte("You learned Go in Y minutes!"))
+}
+
+func requestServer() {
+	resp, err := http.Get("http://localhost:8080")
+	fmt.Println(err)
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	fmt.Printf("\nWebserver said: `%s`", string(body))
+}
+```
+
+## Further Reading
+
+The root of all things Go is the [official Go web site](http://golang.org/).
+There you can follow the tutorial, play interactively, and read lots.
+Aside from a tour, [the docs](https://golang.org/doc/) contain information on
+how to write clean and effective Go code, package and command docs, and release history.
+
+The language definition itself is highly recommended. It's easy to read
+and amazingly short (as language definitions go these days.)
+
+You can play around with the code on [Go playground](https://play.golang.org/p/tnWMjr16Mm). Try to change it and run it from your browser! Note that you can use [https://play.golang.org](https://play.golang.org) as a [REPL](https://en.wikipedia.org/wiki/Read-eval-print_loop) to test things and code in your browser, without even installing Go.
+
+On the reading list for students of Go is the [source code to the standard
+library](http://golang.org/src/pkg/). Comprehensively documented, it
+demonstrates the best of readable and understandable Go, Go style, and Go
+idioms. Or you can click on a function name in [the
+documentation](http://golang.org/pkg/) and the source code comes up!
+
+Another great resource to learn Go is [Go by example](https://gobyexample.com/).
+
+Go Mobile adds support for mobile platforms (Android and iOS). You can write all-Go native mobile apps or write a library that contains bindings from a Go package, which can be invoked via Java (Android) and Objective-C (iOS). Check out the [Go Mobile page](https://github.com/golang/go/wiki/Mobile) for more information.