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diff --git a/es-es/go-es.html.markdown b/es-es/go-es.html.markdown new file mode 100644 index 00000000..5bc4844f --- /dev/null +++ b/es-es/go-es.html.markdown @@ -0,0 +1,299 @@ +--- +name: Go +category: language +language: Go +filename: learngo.go +contributors: + - ["Sonia Keys", "https://github.com/soniakeys"] + +translators: + - ["Adrian Espinosa", "http://www.adrianespinosa.com"] + +--- + +Go fue creado por la necesidad de hacer el trabajo rápidamente. No es la última +tendencia en informática, pero es la forma nueva y más rápida de resolver probemas reales. + +Tiene conceptos familiares de lenguajes imperativos con tipado estático. +Es rápido compilando y rápido al ejecutar, añade una concurrencia fácil de entender para las CPUs de varios núcleos de hoy en día, y tiene características que ayudan con la programación a gran escala. +Go viene con una librería estándar muy buena y una comunidad entusiasta. + +```go +// Comentario de una sola línea +/* Comentario + multi línea */ + +// La cláusula package aparece al comienzo de cada archivo fuente. +// Main es un nombre especial que declara un ejecutable en vez de una librería. +package main + +// La declaración Import declara los paquetes de librerías referenciados en este archivo. +import ( + "fmt" // Un paquete en la librería estándar de Go + "net/http" // Sí, un servidor web! + "strconv" // Conversiones de cadenas +) + +// Definición de una función. Main es especial. Es el punto de entrada para el ejecutable. +// Te guste o no, Go utiliza llaves. +func main() { + // Println imprime una línea a stdout. + // Cualificalo con el nombre del paquete, fmt. + fmt.Println("Hello world!") + + // Llama a otra función de este paquete. + beyondHello() +} + +// Las funciones llevan parámetros entre paréntesis. +// Si no hay parámetros, los paréntesis siguen siendo obligatorios. +func beyondHello() { + var x int // Declaración de una variable. Las variables se deben declarar antes de // utilizarlas. + x = 3 // Asignación de variables. + // Declaración "corta" con := para inferir el tipo, declarar y asignar. + y := 4 + sum, prod := learnMultiple(x, y) // función devuelve dos valores + fmt.Println("sum:", sum, "prod:", prod) // simple salida + learnTypes() // < y minutes, learn more! +} + +// Las funciones pueden tener parámetros y (múltiples!) valores de retorno. +func learnMultiple(x, y int) (sum, prod int) { + return x + y, x * y // devolver dos valores +} + +// Algunos tipos incorporados y literales. +func learnTypes() { + // La declaración corta suele darte lo que quieres. + s := "Learn Go!" // tipo cadena + + s2 := ` Un tipo cadena "puro" puede incluir +saltos de línea.` // mismo tipo cadena + + // Literal no ASCII. Los fuentes de Go son UTF-8. + g := 'Σ' // tipo rune, un alias de uint32, alberga un punto unicode. + f := 3.14195 // float64, el estándar IEEE-754 de coma flotante 64-bit + c := 3 + 4i // complex128, representado internamente por dos float64 + // Sintaxis Var con inicializadores. + var u uint = 7 // sin signo, pero la implementación depende del tamaño como en int + var pi float32 = 22. / 7 + + // Sintáxis de conversión con una declaración corta. + n := byte('\n') // byte es un alias de uint8 + + // Los Arrays tienen un tamaño fijo a la hora de compilar. + var a4 [4]int // un array de 4 ints, inicializados a 0 + a3 := [...]int{3, 1, 5} // un array de 3 ints, inicializados como se indica + + // Los Slices tienen tamaño dinámico. Los arrays y slices tienen sus ventajas + // y desventajas pero los casos de uso para los slices son más comunes. + s3 := []int{4, 5, 9} // Comparar con a3. No hay puntos suspensivos + s4 := make([]int, 4) // Asigna slices de 4 ints, inicializados a 0 + var d2 [][]float64 // solo declaración, sin asignación + bs := []byte("a slice") // sintaxis de conversión de tipo + + 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 underbar lets you "use" a variable but discard its value. + _, _, _, _, _, _, _, _, _ = 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 +} + +// 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() int { + return 1e6 +} + +func learnFlowControl() { + // If statements require brace brackets, and do not require parens. + 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 := 1 + switch x { + case 0: + case 1: + // cases don't "fall through" + case 2: + // unreached + } + // Like if, for doesn't use parens either. + for x := 0; x < 3; x++ { // ++ is a statement + fmt.Println("iteration", x) + } + // x == 1 here. + + // For is the only loop statement in Go, but it has alternate forms. + 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. + if y := expensiveComputation(); y > x { + x = y + } + // Function literals are closures. + xBig := func() bool { + 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 + + // When you need it, you'll love it. + goto love +love: + + learnInterfaces() // Good stuff coming up! +} + +// 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 + + 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. + 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 + // 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 <-cc: // 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() { + // ListenAndServe first parameter is TCP address to listen at. + // Second parameter is an interface, specifically http.Handler. + err := http.ListenAndServe(":8080", pair{}) + fmt.Println(err) // don't ignore errors +} + +// 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!")) +} +``` + +## 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. + +The language definition itself is highly recommended. It's easy to read +and amazingly short (as language definitions go these days.) + +On the reading list for students of Go is the source code to the standard +library. Comprehensively documented, it demonstrates the best of readable +and understandable Go, Go style, and Go idioms. Click on a function name +in the documentation and the source code comes up! + |