迭代器与closure

function allwords()  local line=io.read()  local pos=1  return function()    while line do       local s,e=string.find(line,"%w+",pos)      if s then        pos=e+1        return string.sub(line,s,e)      else        line=io.read()        pos=1      end    end    print("function endddddddddd")    return nil  endendfor word in allwords() do  print(11111)  print(word)end

 无状态的迭代器

local function iter(a,i)  i=i+1  local v=a[i]  if v then     return i,v  endendfunction ipairs(a)--  return iter,a,0 --正确--for获得3个值,迭代器函数,恒定状态,以及控制变量  return iter(a,1) --错误enda={
   4,5,6,7}--for k,v in ipairs(a) do --  print(k,v)--endfor k,v in next,a do  print(k,v)end

 复杂迭代器

--复杂迭代器,不需要定义局部变量poslocal iteratorfunction allwords()  local state={line=io.read(),pos=1}  return iterator,stateendfunction iterator(state)  while state.line do    local s,e=string.find(state.line,"%w+",state.pos)    if s then       state.pos=e+1      return string.sub(state.line,s,e)    else      state.line=io.read()      state.pos=1    end  end  return nilendfor word in allwords() do  print(11111)  print(word)end

 真实迭代器

 

function allwords(f)  for line in io.lines() do    for word in string.gmatch(line,"%w+") do      f(word)    end  endendallwords(print)