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Match.span

spangroupdefault

Group: Metadata

Documentation​

Gets the grapheme span matched by the group with the provided identifier, or a default value if the group did not participate in the match. If no such group exists for the provided identifier, a No_Such_Group is returned.

Arguments​

  • group: The integer index or name of that group.

Remarks​

The Full Match​

The group with index 0 is always the full match of the pattern.

Named Groups by Index​

If the regex contained named groups, these may also be accessed by index based on their position in the pattern.

What is a Character?​

A character is defined as an Extended Grapheme Cluster, see Unicode Standard Annex 29. This is the smallest unit that still has semantic meaning in most text-processing applications.

Note that it is possible for a group to "not participate in the match", for example with a disjunction. In the example below, the "(d)" group does not participate -- it neither matches nor fails.

"ab((c)|(d))".find "abc"

In this case, the group id for "(d)", which is 3, is a valid group id and (Regex.lookup_group 3) will return 3. If the caller tries to get group 3, Match.span will return the default value.