Elixir case

​case​允许我们将一个值与多个模式进行匹配，直到匹配成功：

iex> case {1, 2, 3} do
...>   {4, 5, 6} ->
...>     "This clause won't match"
...>   {1, x, 3} ->
...>     "This clause will match and bind x to 2 in this clause"
...>   _ ->
...>     "This clause would match any value"
...> end
"This clause will match and bind x to 2 in this clause"

如果你想对已存在的变量进行模式匹配，你需要使用操作符：​^​

iex> x = 1
1
iex> case 10 do
...>   ^x -> "Won't match"
...>   _  -> "Will match"
...> end
"Will match"

卫语句中允许包含额外的条件：

iex> case {1, 2, 3} do
...>   {1, x, 3} when x > 0 ->
...>     "Will match"
...>   _ ->
...>     "Would match, if guard condition were not satisfied"
...> end
"Will match"

第一条语句在x是正数时才能匹配。