Go: How To Create a 2D Matrix Properly?

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Slice or Array?

In Go, array can only be created by constant int

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arr := [4]int // works

size := 4
arr := [size]int // Not work!

Thus use slice, if we want to implement a function that create a N size matrix

Implement

straight forward

  • bad memory using, not contiguous matrix
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func newMatrix(s int) [][]int {
    
    m := make([][]int, s)
    
    // Wrong!
    //
    // for _, row := range m {
    //     row = make([]int, s)
    // }
    //
    
    for i, _ := range m {
        m[i] = make([]int, s)
    }
    
    return m
}

method 2

  • ensure to get a contiguous matrix
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func newMatrix(s int) [][]int {
	// allocate the whole space of the matrix
	spaces := make([]int, s*s)

	// create an empty matrix: [[] [] []...]
	m := make([][]int, s)

	// assign spaces to the matrix
	i, j := 0, 0
	for i < s {
		m[i] = spaces[j : j+s]
		i++
		j += s
	}

	return m
}

Generic

more flexiable!

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func newMatrix[T any](s int) [][]T {
	// allocate the whole space of the matrix
	spaces := make([]T, s*s)

	// create an empty matrix: [[] [] []...]
	m := make([][]T, s)

	// assign spaces to the matrix
	i, j := 0, 0
	for i < s {
		m[i] = spaces[j : j+s]
		i++
		j += s
	}

	return m
}

Usage

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m := newMatrix[unit](3) // [[0 0 0] [0 0 0] [0 0 0]]

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