Universe
Related Doc:
package dregex
Regular expressions can have character classes and wildcards.
Regular expressions can have character classes and wildcards. In order to produce a NFA, they should be expanded to disjunctions. As the base alphabet is Unicode, just adding a wildcard implies a disjunction of more than one million code points. Same happens with negated character classes or normal classes with large ranges.
To prevent this, the sets are not expanded to all characters individually, but only to disjoint intervals.
Example:
[abc] -> a-c [efg] -> 0-c|h-MAX mno[efg] -> def(0-c|h-l|m|n|o|p-MAX) . -> 0-MAX
Care must be taken when the regex is meant to be used for an operation with another regex (such as intersection or difference). In this case, the sets must be disjoint across all the "universe"
This method collects the interval, so they can then be made disjoint.
Represent the set of characters that is the union of the sets of characters of a group of regular expressions. Regex must belong to the same Universe to be able to make operations between them.