function - 高语 : Return 2d slice for any type

Question

我知道如何创建这样的二维 slice 。

var data []int
data = make([]int, w*h)
v := make([][]int, h)
for i := 0; i < h; i++ {
    v[i] = data[w*i : w*(i+1)]
}

由于这非常冗长，而且我将创建其中的许多内容，因此我决定将其重构为一个函数。

func create2dSlice(w, h int) [][]int {
    var data []int
    data = make([]int, w*h)
    v := make([][]int, h)
    for i := 0; i < h; i++ {
        v[i] = data[w*i : w*(i+1)]
    }
    return v
}

func main() {
    a := create2dSlice(3, 2)
}

这只适用于整数。在 golang 中有什么方法可以对重用相同代码的其他类型执行此操作？

我来自 C++，我希望能够做这样的事情。

create2dSlice<int>(w, h)

Answer 1

Go 没有泛型。对于矩阵，类似的问题，我在 snippet 文件夹中的 matrix.go 文件中有一个 NewMatrix 函数。按照设计，我可以简单地复制它并将 []int 全局更改为另一种类型，例如 []float64。

您可以通过为 w slice 提供有效容量来改进您的功能。

例如，

package main

import "fmt"

func NewMatrix(r, c int) [][]int {
    a := make([]int, c*r)
    m := make([][]int, r)
    lo, hi := 0, c
    for i := range m {
        m[i] = a[lo:hi:hi]
        lo, hi = hi, hi+c
    }
    return m
}

func create2dSlice(w, h int) [][]int {
    a := make([]int, w*h)
    s := make([][]int, h)
    lo, hi := 0, w
    for i := range s {
        s[i] = a[lo:hi:hi]
        lo, hi = hi, hi+w
    }
    return s
}

func main() {
    r, c := 2, 3
    m := NewMatrix(r, c)
    fmt.Println(m)
    w, h := c, r
    a := create2dSlice(w, h)
    fmt.Println(a)
}

输出:

[[0 0 0] [0 0 0]]
[[0 0 0] [0 0 0]]

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The Go Programming Language Specification

Slice expressions

Slice expressions construct a substring or slice from a string, array, pointer to array, or slice. There are two variants: a simple form that specifies a low and high bound, and a full form that also specifies a bound on the capacity.

Full slice expressions

For an array, pointer to array, or slice a (but not a string), the primary expression

a[low : high : max]

constructs a slice of the same type, and with the same length and elements as the simple slice expression a[low : high]. Additionally, it controls the resulting slice's capacity by setting it to max - low.