Re: common prefix?
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- Subject: Re: common prefix?
- From: Duncan Cross <duncan.cross@...>
- Date: 2009年7月17日 15:26:52 +0100
On Fri, Jul 17, 2009 at 2:56 PM, Andre<arpin@kingston.net> wrote:
> Petite Abeille <petite.abeille <at> gmail.com> writes:
>
>>
>> Hello,
>>
>> Does anyone has a little function to compute the common prefix of a
>> list of strings?
>>
>> E.g.:
>>
>> local aList = { 'foobarbaz', 'foobar', 'foo' }
>>
>> print( CommonPrefix( aList ) )
>>
>> > foo
>>
>> TIA.
>>
>> Cheers,
>>
>> PA.
>>
>> P.S.
>>
>
> I think this is really a matching problem
I can't see any reason to use:
string.match(v, '^'..prefix)
...instead of:
(string.sub(v,1,#prefix)==prefix)
...and using match also has the disadvantage that your prefix cannot
include any of the "magic" matching characters like . [ ] % etc. Of
course you can use a gsub to prefix these with % beforehand.
Also I have a simpler suggested implementation to replace my earlier one:
--
function commonprefix(list)
local prefix
for i,v in ipairs(list) do
if (i == 1) then
prefix = v
else
if (string.sub(v,1,#prefix) ~= prefix) then
for i=1,#prefix do
if (string.sub(v,i,i) ~= string.sub(prefix,i,i)) then
prefix = string.sub(prefix,1,i-1)
break
end
end
end
end
if (#prefix == 0) then
break
end
end
return prefix or ''
end
--
-Duncan