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- Subject: Re: Function to return relative path?
- From: Jerome Vuarand <jerome.vuarand@...>
- Date: Fri, 29 Nov 2013 10:58:32 +0000
2013/11/29 Paul Merrell <email@example.com>:
> To avoid reinventing the wheel, I thought I'd ask whether anyone has a
> function that will return a relative path from absolute paths for the
> current and destination directories? Something along the lines of:
> function(curdir, destdir)
> return reldir
> I googled around but found only a function that has dependencies.
I wrote a path module that might help you implement your function:
In case you're wondering (and didn't click the link) you can install
it with LuaRocks.
As for your specific function, it could look something like that:
local path = require 'path'
function relative(from, to)
if path.type(from)~='path' then from = path.split(from) end
if path.type(to)~='path' then to = path.split(to) end
-- determine where paths diverge
local i = 0
while from:sub(0, i) == to:sub(0, i) do
i = i + 1
-- roots may be different
if i == 0 then return nil end
from = from:sub(i)
to = to:sub(i)
-- invert from
local morf = path.empty
for i=1,#from do
morf = morf / '..'
return morf / to
assert(relative([[C:\Program Files (x86)\MyApp\bin]],
[[C:\Windows\system32]]) == path.split('../../../Windows/system32'))
Note that I just fixed a small bug in the == operator, which could
give false negatives for relative paths. If that's a problem for you
use the Mercurial tip instead of the rock.