Module:Sortkey

 localgetArgs=require('Module:Arguments').getArgs

 localp={}

 functionp._encode(sortkey)
 -- Protect against sortkey nesting.
 -- Example: {{sort|{{dts|2013|07|07}}|{{dts|1990|12|01}}}}
 ifstring.find(sortkey,"sortkey")orstring.find(sortkey,"data-sort-value")then
 return"";
 end
 returnmw.text.encode(sortkey)
 end

 functionp.encode(frame)
 localargs=getArgs(frame);
 returnp._encode(args[1]or"")
 end

 localfunctionvalid_number(num)
 -- Return true if num is a valid number.
 -- In Scribunto (different from some standard Lua), when expressed as a string,
 -- overflow or other problems are indicated with text like "inf" or "nan"
 -- which are regarded as invalid here (each contains "n").
 iftype(num)=='number'andtostring(num):find('n',1,true)==nilthen
 returntrue
 end
 end

 functionp._sortKeyForNumber(value)
 localsortkey
 ifnotvalid_number(value)then
 ifvalue<0then
 sortkey='1000000000000000000'
 else
 sortkey='9000000000000000000'
 end
 elseifvalue==0then
 sortkey='5000000000000000000'
 else
 localmag=math.floor(math.log10(math.abs(value))+1e-14)
 localprefix
 ifvalue>0then
 prefix=7000+mag
 else
 prefix=2999-mag
 value=value+10^(mag+1)
 end
 sortkey=string.format('%d',prefix)..string.format('%015.0f',math.floor(value*10^(math.min(28,14-mag))))
 end
 returnsortkey;
 end

 functionp.sortKeyForNumber(frame)
 localargs=getArgs(frame);
 returnp._sortKeyForNumber(args[1]or"")
 end

 returnp