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77 lines
2.0 KiB
Go
77 lines
2.0 KiB
Go
// _Slices_ are a key data type in Go, giving a more
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// powerful interface to sequences than arrays.
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package main
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import "fmt"
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func main() {
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// Unlike arrays, slices are typed only by the
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// elements they contain (not the number of elements).
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// To create an empty slice with non-zero length, use
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// the builtin `make`. Here we make a slice of
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// `string`s of length `3` (initially zero-valued).
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s := make([]string, 3)
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fmt.Println("emp:", s)
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// We can set and get just like with arrays.
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s[0] = "a"
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s[1] = "b"
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s[2] = "c"
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fmt.Println("set:", s)
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fmt.Println("get:", s[2])
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// `len` returns the length of the slice as expected.
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fmt.Println("len:", len(s))
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// In addition to these basic operations, slices
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// support several more that make them richer than
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// arrays. One is the builtin `append`, which
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// returns a slice containing one or more new values.
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// Note that we need to accept a return value from
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// `append` as we may get a new slice value.
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s = append(s, "d")
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s = append(s, "e", "f")
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fmt.Println("apd:", s)
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// Slices can also be `copy`'d. Here we create an
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// empty slice `c` of the same length as `s` and copy
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// into `c` from `s`.
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c := make([]string, len(s))
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copy(c, s)
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fmt.Println("cpy:", c)
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// Slices support a "slice" operator with the syntax
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// `slice[low:high]`. For example, this gets a slice
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// of the elements `s[2]`, `s[3]`, and `s[4]`.
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l := s[2:5]
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fmt.Println("sl1:", l)
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// This slices up to (but excluding) `s[5]`.
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l = s[:5]
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fmt.Println("sl2:", l)
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// And this slices up from (and including) `s[2]`.
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l = s[2:]
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fmt.Println("sl3:", l)
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// We can declare and initialize a variable for slice
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// in a single line as well.
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t := []string{"g", "h", "i"}
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fmt.Println("dcl:", t)
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// Slices can be composed into multi-dimensional data
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// structures. The length of the inner slices can
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// vary, unlike with multi-dimensional arrays.
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twoD := make([][]int, 3)
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for i := 0; i < 3; i++ {
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innerLen := i + 1
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twoD[i] = make([]int, innerLen)
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for j := 0; j < innerLen; j++ {
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twoD[i][j] = i + j
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}
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}
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fmt.Println("2d: ", twoD)
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}
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