Lua矩阵转置：行列互换的原地交换

-- 错误：非方形也硬套原地交换，行列越界
for i = 1, #m do
    for j = 1, #m[1] do
        m[i][j], m[j][i] = m[j][i], m[i][j]
    end
end

local function transpose(m)
    local n = #m
    for i = 1, n do
        for j = i + 1, n do
            m[i][j], m[j][i] = m[j][i], m[i][j]
        end
    end
    return m
end
local grid = transpose({{1, 2}, {3, 4}})
local label = panel:getChildByName("trText")
label:setString(grid[1][2] .. "/" .. grid[2][1])