# 【Lua】【型別】 nil - 布林

## nil

`nil`是Lua裡的一個特殊值，**代表什麼也沒有**。其型別也是`nil`

```Lua
type(nil) -- => nil
```

## 布林

#### <span class="s1">布林值只有</span><span style="background-color: #ffff99;">true</span><span class="s1">和</span><span style="background-color: #ffff99;">false</span>

#### 只要不是<span style="background-color: #ffff00;"><span style="font-family: Lucida Console, DejaVu Sans Mono, Ubuntu Mono, Monaco, monospace;"><span style="font-size: 19.5922px; white-space: pre-wrap; background-color: #ffff00;">nil</span></span></span>或是<span style="background-color: #ffff00;"><span style="font-family: Lucida Console, DejaVu Sans Mono, Ubuntu Mono, Monaco, monospace;"><span style="font-size: 19.5922px; white-space: pre-wrap; background-color: #ffff00;">false</span></span></span>都為真， **包含0、空表、空字串** 。

```Lua
if 0 then
  print("0 is true")
end

if {} then
  print("{} is true")
end

if "" then
  print [["" is true]]
end
```

#### ~= 不等於

```Lua
weeks = {"週一","週二","週三","週四","週五","週六","週日", "Opps"}

if #weeks ~= 7 then
  error("Weeks length must is 7.")
end
```