Re: strings
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: strings
- From: Michal Kolodziejczyk <miko@...>
- Date: 2009年12月16日 15:05:39 +0100
On 16.12.2009 15:01, Hans Hagen wrote:
> steve donovan wrote:
>> On Wed, Dec 16, 2009 at 3:29 PM, Hans Hagen <pragma@wxs.nl> wrote:
>>> The following is valid lua
>>>
>>> a = "text"
>>> b = a[3]
>>
>> Yes, given that there is no index operator for strings it seems odd
>> that we don't get an error. The reason is that strings have a
>> metatable with __index pointing to the string table; looking up [3] on
>> s leads to string[3] which gives the nil as you've noticed.
>>
>> If you're prepared to modify the metatable of all strings, then you
>> can define a[3] in this case to be a:sub(3,3)
>
> can you give an example? __index gets a (table, n) passed and not the
> string itself
Check this out:
s="qwerty"
MT=getmetatable(s)
MT.__index=function(obj,key)
if type(key)=='number' then
local char=obj:sub(key, key)
assert(#char>0, "Illegal index: "..key.." for string "..obj)
return char
else
return string[key]
end
end
print(s[3]..s[2])
print(s[9])
Regards,
miko