Golang matrix multiplication

matmul.go

package main

import (
	"fmt"
	"reflect"
	"strconv"
)

type matrix [][]int

func (m matrix) size() (int, int) {
	return len(m), len(m[0])
}

func (m matrix) toString() (ret string) {
	for i := range m {
		for _, a := range m[i] {
			ret += strconv.Itoa(a) + "\t"
		}
		ret += "\n"
	}
	return ret
}

func (m matrix) mul(other matrix) matrix {
	h, w := m.size()
	oh, ow := other.size()
	if w != oh {
		panic("Can't do multiplication.")
	}
	ret := make(matrix, h)
	for i := range ret {
		ret[i] = make([]int, ow)
		for j := range ret[i] {
			for k := 0; k < w; k++ {
				ret[i][j] += m[i][k] * other[k][j]
			}
		}
	}
	return ret
}

func main() {
	mat1 := matrix{
		[]int{2, 3},
		[]int{1, 4},
		[]int{2, 1},
	}
	mat2 := matrix{
		[]int{3, 1, 2},
		[]int{2, 4, 2},
	}

	got := mat1.mul(mat2)
	
	var expect matrix

	// success case (no output)
	expect = matrix{
		[]int{12, 14, 10},
		[]int{11, 17, 10},
		[]int{8, 6, 6},
	}

	if !reflect.DeepEqual(expect, got) {
		fmt.Printf("expect:\n%s\nbut got:\n%s\n", expect.toString(), got.toString())
	}

	// fail case
	expect = *new(matrix)

	if !reflect.DeepEqual(expect, got) {
		fmt.Printf("expect:\n%s\nbut got:\n%s\n", expect.toString(), got.toString())
	}
}

output

expect:

but got:
12      14      10
11      17      10
8       6       6