Module:Path

 require[[strict]]
 localfunctionsplit_path(path)
 localparts={}
 locallen=0
 fortokeninpath:gmatch("[^/]+")do
 len=len+1
 parts[len]=token
 end
 returnparts,len
 end


 localfunctionget_abs_path(current,page)
 localtbl_i,len_i=split_path(page)
 localtbl_o
 locallen_o
 iftbl_i[1]=='.'ortbl_i[1]=='..'then
 tbl_o,len_o=split_path(current)
 else
 tbl_i[1]=tbl_i[1]:gsub('^([^:]?)([^:]*)(:?)(.?)',
 function(s1,s2,s3,s4)
 ifs3==''thenreturns1:upper()..s2end
 returns1:upper()..s2..s3..s4:upper()
 end,
 1
 )
 tbl_o={}
 len_o=0
 end
 forkey,valinipairs(tbl_i)do
 ifval=='..'then
 iflen_o<1then
 error('Module:Path: invalid path',0)end
 tbl_o[len_o]=nil
 len_o=len_o-1
 elseifval~='.'then
 len_o=len_o+1
 tbl_o[len_o]=val
 end
 end
 iflen_o<1then
 tbl_o[1]=''
 len_o=1
 end
 returntbl_o,len_o
 end


 localfunctionget_rel_path(current,page,add_prefixes)
 localtbl_i,len_i=get_abs_path(current,page)
 localtbl_c,len_c=split_path(current)
 localtbl_o={}
 locallen_o=0
 localminlen
 localnew_at=0
 iflen_c<len_ithenminlen=len_celseminlen=len_iend
 foridx=1,minlendo
 iftbl_c[idx]~=tbl_i[idx]then
 new_at=idx
 break
 end
 end
 ifnew_at==1thenreturntable.concat(tbl_i,'/')end
 ifadd_prefixesthen
 ifnew_at==0then
 tbl_o[1]='.'
 new_at=minlen+1
 end
 foridx=new_at,len_cdo
 len_o=len_o+1
 tbl_o[len_o]='..'
 end
 iflen_o<1thenlen_o=1end
 elseifnew_at==0thennew_at=minlen+1end
 foridx=new_at,len_ido
 len_o=len_o+1
 tbl_o[len_o]=tbl_i[idx]
 end
 returntable.concat(tbl_o,'/')
 end


 localiface={}


 iface.abs=function(frame)
 localpage=frame.args[1]
 ifpage~=nilthenpage=page:match'^%s*(.*%S)'end
 ifpage==nilthenreturnmw.title.getCurrentTitle().prefixedTextend
 localretval,_=table.concat(get_abs_path(
 mw.title.getCurrentTitle().prefixedText,
 page:gsub('^%s*/%s*','./',1)
 ),'/')
 returnretval
 end


 iface.rel=function(frame)
 localpage=frame.args[1]
 ifpage~=nilthenpage=page:match'^%s*(.*%S)'end
 ifpage==nilthenreturn'.'end
 returnget_rel_path(mw.title.getCurrentTitle().prefixedText,
 page:gsub('^%s*/%s*','./',1),true)
 end


 iface.sub=function(frame)
 localpage=frame.args[1]
 ifpage~=nilthenpage=page:match'^%s*(.*%S)'end
 ifpage==nilthenreturn''end
 returnget_rel_path(mw.title.getCurrentTitle().prefixedText,
 page:gsub('^%s*/%s*','./',1),false)
 end


 returniface