Regex.find

Regex.isMatch reports whether a match exists anywhere in the input. Regex.find returns Some containing the first match or None() when no match exists. Regex.findAll returns every nonoverlapping match in search order and returns an empty array when no match exists.

Search begins at the earliest Unicode scalar boundary that permits the complete pattern to match. At that position alternatives are tried in pattern order. Greedy repetitions prefer more scalars and lazy repetitions prefer fewer scalars while still allowing the rest of the pattern to match.

After a nonempty match, findAll resumes at its exclusive end. After an empty match, it resumes at the next Unicode scalar boundary. An empty match directly at the end of the preceding nonempty match is skipped and search advances to the next scalar boundary.

An empty pattern visits every scalar boundary, including both ends. The empty input has one boundary and produces one empty match for an empty pattern. Matching never splits the UTF-8 bytes of a scalar.

Regex.split and Regex.replaceAll use the same ordered match sequence as findAll. Repeated calls start a new search and do not retain a cursor. The input string and compiled pattern are unchanged.

The receiver is evaluated once before the positional arguments, which are evaluated once from left to right. Search does not invoke user callbacks or access external state. No match is an ordinary result and does not produce a diagnostic.

Match.start and Match.end are read-only nonnegative UTF-8 byte offsets in the original input. They follow the inclusive start and exclusive end of byte intervals. Both are scalar boundaries and the end does not exceed the UTF-8 byte length of the input.

Match.text is the matched substring. An empty match has equal start and end and an empty text value. The offsets are not string grapheme indexes. A match may select a combining mark inside a grapheme.

Encoding the original input with encodeUtf8, slicing its bytes from start to end, and calling decodeUtf8 returns Ok containing Match.text. This relationship also holds for non-ASCII input.

Match.groups returns an independent array indexed by capture number. Entry zero is Some containing the entire match. Capturing parentheses are numbered from one in opening-parenthesis order. Named groups participate in the same numbering and noncapturing groups do not.

A nonparticipating capture has value None(). A participating empty capture has value Some containing an empty string. A repeated capture retains the last participating capture in the selected match.

Match.named returns an independent map from capture names to captured strings. A nonparticipating named capture is absent. A participating empty named capture is present with an empty string. Names are inserted in ascending ASCII order.

Reading a Match field evaluates its receiver once and does not modify the Match or input. Mutating a groups array or named map does not affect a later field read. Field access cannot fail for a Match value.