The abstract type for a character set.

Synonym of charset.

The empty character set.

The full character set.

singleton c returns a charset containing only c.

range cmin cmax returns the charset containing all the characters between cmin and cmax.

from_string s returns the charset corresponding to the description string s, which may contain standalone characters (different from '-', which is only allowed as first character) or ranges. They are build of start and end characters, separated by '-'. An example of a valid description is "-_a-zA-Z0-9". Note that Invalid_argument is raised in case of ill-formed description.

union cs1 cs2 builds a new charset that contins the union of the characters of cs1 and cs2.

complement cs returns a new charset containing exactly characters that are not in cs.

add cs c returns a new charset containing the characters of cs and the character c.

del cs c returns a new charset containing the characters of cs but not the character c.

mem cs c tests whether the charset cs contains c.

print oc cs prints the charset cs to the output channel oc. A compact format is used for printing: common ranges are used and full and empty charsets are abreviated.

print_full oc cs is the same as print oc cs but it does not use abreviations (i.e. all characters are displayed).

show oc cs builds a string representing the charset cs using the same compact format as print.

show_full oc cs is the same as show oc cs but it does not use abreviations (i.e. all characters appear).

copy cs make a copy of the charset cs.

addq cs c adds the character c to the charset cs. Users must be particularly careful when using this function. In particular, it should not be used directly on empty, full or the result of the singleton function as it would change their value permanently. It is advisable to prefer the use of add or to work on a copy.

delq cs c deletes the character c from the charset cs. Similar recomendatiosn as for addq apply.