diff options
Diffstat (limited to 'go.html.markdown')
| -rw-r--r-- | go.html.markdown | 35 |
1 files changed, 33 insertions, 2 deletions
diff --git a/go.html.markdown b/go.html.markdown index ae99535b..739ec05d 100644 --- a/go.html.markdown +++ b/go.html.markdown @@ -12,6 +12,7 @@ contributors: - ["Alexej Friesen", "https://github.com/heyalexej"] - ["Clayton Walker", "https://github.com/cwalk"] - ["Leonid Shevtsov", "https://github.com/leonid-shevtsov"] + - ["Michael Graf", "https://github.com/maerf0x0"] --- Go was created out of the need to get work done. It's not the latest trend @@ -30,6 +31,12 @@ Go comes with a good standard library and a sizeable community. /* Multi- line comment */ + /* A build tag is a line comment starting with // +build + and can be execute by go build -tags="foo bar" command. + Build tags are placed before the package clause near or at the top of the file + followed by a blank line or other line comments. */ +// +build prod, dev, test + // A package clause starts every source file. // Main is a special name declaring an executable rather than a library. package main @@ -102,6 +109,11 @@ can include line breaks.` // Same string type. a5 := [...]int{3, 1, 5, 10, 100} // An array initialized with a fixed size of five // elements, with values 3, 1, 5, 10, and 100. + // Arrays have value semantics. + a4_cpy := a4 // a4_cpy is a copy of a4, two separate instances. + a4_cpy[0] = 25 // Only a4_cpy is changed, a4 stays the same. + fmt.Println(a4_cpy[0] == a4[0]) // false + // 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 a5. No ellipsis here. @@ -109,6 +121,11 @@ can include line breaks.` // Same string type. var d2 [][]float64 // Declaration only, nothing allocated here. bs := []byte("a slice") // Type conversion syntax. + // Slices (as well as maps and channels) have reference semantics. + s3_cpy := s3 // Both variables point to the same instance. + s3_cpy[0] = 0 // Which means both are updated. + fmt.Println(s3_cpy[0] == s3[0]) // true + // 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, @@ -161,10 +178,11 @@ func learnNamedReturns(x, y int) (z int) { // 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. +// Unlike in C/Cpp taking and returning an address of a local varible is also safe. 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. + // The allocated int slice 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. @@ -190,7 +208,7 @@ func learnFlowControl() { x := 42.0 switch x { case 0: - case 1: + case 1, 2: // Can have multiple matches on one case case 42: // Cases don't "fall through". /* @@ -202,6 +220,19 @@ func learnFlowControl() { default: // Default case is optional. } + + // Type switch allows switching on the type of something instead of value + var data interface{} + data = "" + switch c := data.(type) { + case string: + fmt.Println(c, "is a string") + case int64: + fmt.Printf("%d is an int64\n", c) + default: + // all other cases + } + // 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. |