1) 给params的list转小写 匿名函数
例: params = [“A”,“B”,“C”]
Enum.map(params, fn (x) -> String.downcase(x) end )
或者 Enum.map(parmas, fn x -> String.downcase(x) end)
输出为:["a","b","c"]
2)Enum.map
iex下输入:
Enum.map(%{"a"=>"1" , "b"=>"2" },fn {k,v} -> k <> v end )
["a1", "b2"]
输入:
iex(1)>Enum.map([1,2,3],fn x -> x*2 end )
[2, 4, 6]
iex(2)> Enum.map(%{1=>2 , 3=>4 },fn {k,v} -> k * v end )
[2, 12]
遍历列表:
def sum([]) do
0
end
def sum([head|tail]) do
head + sum(tail)
end
iex(1)> MyProject.sum([1,2,3])
6
例子2:
def double_each([head | tail]) do
[head * 2 | double_each(tail)]
end
def double_each([]) do
[]
end
输出:
iex(2)> MyProject.double_each([1,2,3])
[2, 4, 6]
Enum.map_jon()
iex(1)> list = [1,2,3]
iex(2)> list |> Enum.map_join("=", fn x -> Integer.to_string(x) end)
"1=2=3"
iex(3)> list |> Enum.map_join(fn x -> "=" <> Integer.to_string(x) end)
"=1=2=3"
iex> Enum.map_join([1, 2, 3], &(&1 * 2))
"246"
iex> Enum.map_join([1, 2, 3], " = ", &(&1 * 2))
"2 = 4 = 6"
reduce 操作:
Enum.reduce <=> List.foldl
Enum.reduce([1,2,3,4], 0, fn (x,acc) ->x - acc end)
or
Enum.reduce([1,2,3,4], 0, fn (x,acc) ->x - acc end)
List.foldl([1,2,3,4], 0 , fn(x, acc) -> x - acc end )
into(enumerable, collectable)
iex> Enum.into([1, 2], [0])
[0, 1, 2]
iex> Enum.into([a: 1, b: 2], %{})
%{a: 1, b: 2}
iex> Enum.into(%{a: 1}, %{b: 2})
%{a: 1, b: 2}
iex> Enum.into([a: 1, a: 2], %{})
%{a: 2}
关于Agent的操作:
iex(1)> {:ok,pid} = Agent.start_link(fn ->2 end)
{:ok, #PID<0.351.0>}
iex(2)> Agent.cast(pid, fn state -> state + 2 end)
iex(3)> Agent.get(pid,fn state -> state end)
4
iex(4)> Agent.cast(pid, fn state -> state + 3 end)
:ok
iex(5)> Agent.get(pid,fn state -> state end)
7