(:
Hello I have a hopefully not too silly question ...
Is there an easy way to remove the exponent notation and return 30000201_30000000
without working out where the E is in the parts and padding zeros
  ====> <a>
    <d>3.0000201E7_3.0E7</d>
  </a>
:)
declare function local:sumVec($a,$opt){
  let $a := <x>{for $w at $pos in $a
               return
                  for $v at $pos in  tokenize(xs:string($w),"_")
                    return element {'a'} { (attribute {'pos'} {$pos}, try {xs:float($v)} catch * {0} )}
                  }</x>
  let $b :=  string-join(for $w in distinct-values($a//@pos)
               return if ($opt=0) then sum($a/a[@pos=$w]) ,"_")
 return $b  
};

let $a := ''
return  <a>
      <d>{local:sumVec(('10000001_10000000','10000000_10000000','10000000_10000000','100_',100),0)}</d>
</a>