Elixir简单的wordcount小程序

本文来自:fair-jm.iteye.com 转截请注明出处

 

defmodule Wordcount do
   @moduledoc "simple wordcount program by fairjm"
   @nodecount 3
   
   def start(file) do
      s = self
	  spawn(fn -> count(file,s) end)
   end
   
   defp count(file,caller) do
		s = self
		nodes = Enum.map(1..@nodecount,fn _e -> spawn(fn -> countLine end) end)
		count = File.stream!(file)
				|> Enum.reduce(0,fn e,r -> send(Enum.at(nodes,:random.uniform(@nodecount)-1),{e,s});r+1 end)
		IO.puts("total count is #{count}")
		v = countDown(count,%{})
		nodes |> Enum.each(&(send(&1,Stop)))
		send(caller,v)
   end
   
   defp countDown(0,m) do
		IO.puts("ending")
		m
    end
	
   defp countDown(n,m) do
		receive do
			map -> countDown(n-1, Enum.reduce(map,m,fn {k,v},r -> Map.put(r,k,Map.get(r,k,0)+v) end)) 
			after 5000 -> countDown( n-1 , m)
		end
   end
   
   defp countLine do
		receive do
			{line,caller} ->
				IO.puts("#{inspect(self)} is doing work")
				m = line 
					|> String.strip
					|> String.split(" ")
					|> Stream.filter(&(String.length(&1) > 0))
					|> Enum.reduce(%{},fn e,r ->
												case r[e] do
													nil -> Map.put(r,e,1)
													v   -> Map.put(r,e,v+1)
												end
										end
									)
				send(caller,m)
				countLine
			Stop ->
				IO.puts("#{inspect(self)} quits")
			_other ->
				IO.puts("error message")
				countLine
		end
   end
end

 简单的小练习  代码中用三个erlang进程模拟mapper 一个进程模拟reducer  

 elixir的语法比erlang的要平易近人好多

 有兴趣学的同学 推介买一本elixir in action(http://www.manning.com/juric/)

 或者图灵社区有爱的同学整理的教程: http://www.ituring.com.cn/minibook/10831

 此外这位同学的github上也维护着中文学习资料: https://github.com/elixir-lang-cn/programming-elixir