fun  killDuplicates'(ord,0)= ord
|    killDuplicates'(ord,n)=

	if isin(String.substring(ord,0,n),String.sub(ord,n)
	then killDuplicates'(((String.substring(ord,0,n)) ^ (String.substring(ord,n+1,(size(ord) -1 -n)))),n-1)
	else killDuplicates'(ord,n-1);

fun killDuplicates(ord) = killDuplicates'(ord,size(ord)-1); 


fun isin'(ord,tecken,0)= tecken=String.sub(ord,0)
|   isin'(ord,tecken,n)= tecken=String.sub(ord,n) orelse isin'(ord,tecken,n-1);

fun isin(ord,tecken) = isin'(ord,tecken,size(ord)-1);