Converts into an annotation comparison function.
- start : compare annotations by their start position;
- end : compare annotations by their end position;
- length : compare annotations by their length in number of characters;
- order : compare annotations by their start position, then by the inverse of end position;
By prepending reverse- , the comparison is reversed.
A composite comparator may be specified by separating multiple values with commas (“,”). In this case the first comparator is used, if annotations are equal, then the second is used, etc. The order comparator is thus equivalent to start,reverse-end .
COMPARATOR is converted into an annotation comparator as specified by the string conversion.