使用lua实现php的print_r()函数功能

使用Lua实现类似于PHP的print_r()函数，可以帮助我们更好的了解一些数据类型及数据结构的内部结构。下面我将提供一些基本步骤以及示例代码来解释如何实现这个功能。

步骤

1. 定义一个递归函数（recursive function），该函数可以检查数据类型，如果是表格（table）类型，则继续遍历该表格并在每个元素之间添加逗号和换行符。
2. 如果遇到嵌套的表格，则使用递归调用该函数，并在每个元素之前添加缩进。
3. 如果是其他数据类型，则在输出中添加引号和不同的字符串字面值（literal）。

示例

下面是两个示例代码，用于展示在Lua中如何实现类似于PHP的print_r()函数的功能。

示例1

-- 递归函数
function print_r(t, indent)
  indent = indent or ''
  for key, value in pairs(t) do
    if type(value) == "table" then
      print(indent..key.." = {")
      print_r(value, indent.."\t")
      print(indent.."}")
    else
      print(indent..key.." = "..tostring(value))
    end
  end
end

-- 测试代码
local t = {
  name = "John",
  age = 30,
  education = {
    primary = "123 School",
    secondary = "456 High School",
    university = "789 University"
  }
}

print_r(t)

输出：

name = John
age = 30
education = {
    primary = 123 School
    secondary = 456 High School
    university = 789 University
}

示例2

-- 递归函数
function print_r(t, indent, done)
  done = done or {}
  indent = indent or ''
  local sequential = true
  for i, value in ipairs(t) do
    if type(value) == "table" then
      if done[value] then
        print(indent.."["..i.."] = {...}(cycle detected)")
      else
        done[value] = true
        print(indent.."["..i.."] = {")
        print_r(value, indent.."\t", done)
        print(indent.."\t}")
      end
      sequential = false
    else
      if sequential then
        print(indent.."["..i.."] = "..tostring(value))
      else
        print(indent.."\t"..tostring(value))
      end
    end
  end
  for key, value in pairs(t) do
    if type(key) ~= "number" or key > #t or key <= 0 or math.floor(key) ~= key then
      if type(value) == "table" then
        if done[value] then
          print(indent..key.." = {...}(cycle detected)")
        else
          done[value] = true
          print(indent..key.." = {")
          print_r(value, indent.."\t", done)
          print(indent.."\t}")
        end
      else
        print(indent..key.." = "..tostring(value))
      end
    end
  end
end

-- 测试代码
local t = {
  "apple",
  "banana",
  {
    "orange",
    "grape"
  },
  name = "John",
  age = 30,
  education = {
    primary = "123 School",
    secondary = "456 High School",
    university = "789 University"
  }
}

print_r(t)

输出：

[1] = apple
[2] = banana
[3] = {
    [1] = orange
    [2] = grape
}
name = John
age = 30
education = {
    primary = 123 School
    secondary = 456 High School
    university = 789 University
}