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https://yq.aliyun.com/articles/11387

lua "诡异"的return用法

摘要： 在Lua中, return的用法比较"诡异", 为什么这么说呢, 因为它只能用在block结束的地方, 不能用在block的一个中间部分.例如function a() i = 1 return i -- 这里会报错, 提示return后面必须是end, 意思是既然你要return了, 那么就结束这个块吧.

function a()
  i = 1
  return i  -- 这里会报错, 提示return后面必须是end, 意思是既然你要return了, 那么就结束这个块吧.
  i = 2
end

> function a()
>>   i = 1
>>   return i
>>   i = 2
stdin:4: ‘end‘ expected (to close ‘function‘ at line 1) near ‘i‘

> function a()
>>   i = 1
>>   do return i end  -- 这里是允许的.
>>   i = 2
>> end
> print(a())
1

> if i == 1
>> then
>>   return  -- 这里不能使用, 因为下面不是elseif或者else或者end.
>>   i=2
stdin:4: ‘end‘ expected (to close ‘if‘ at line 1) near ‘=‘

if i == 1
then
  return
elseif i == 2
  then
  return
else
  return
end

> for x=1,10,1 do
>> print(x)
>> return
>> print(x+1)
>> end
1
2

> for x=1,10,1 do
print(x)
return
print(x+1) 
x=2
stdin:4: ‘end‘ expected (to close ‘for‘ at line 1) near ‘x‘
> for x=1,10,1 do
print(x)
return
x=2           
stdin:4: ‘end‘ expected (to close ‘for‘ at line 1) near ‘=‘

> for x=1,10,1 do
print(x)
do return end
print(x)
x=2
>> end
1

> repeat do
i=1
print(i)
return 
print(i) 
end until i == 2
1
1
> repeat do
i=1
print(i)
return 
print(i) 
x=2   -- 这里又会报错.
end until i == 2
stdin:4: ‘end‘ expected (to close ‘do‘ at line 1) near ‘x‘

lua "诡异"的return用法

标签：line   stdin   service   list   ==   auth   blog   author   一个   

原文地址：http://www.cnblogs.com/sanyejun/p/7912111.html