Merge pull request #508 from holocronweaver/master

[go/en][go/es] Fix several problems with Go tutorials

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!"))
 }
 ```