Compile compiles the regexp into a program to be executed.

EmptyOpContext returns the zero-width assertions satisfied at the position between the runes r1 and r2.

IsWordChar reports whether r is considered a “word character” during the evaluation of the \b and \B zero-width assertions.

Parse parses a regular expression string s, controlled by the specified Flags, and returns a regular expression parse tree.

allow character classes like [^a-z] and [[:space:]] to match newline.

allow .

Unexpected error.

Parse errors.

case-insensitive match.

treat pattern as literal string.

make repetition operators default to non-greedy.

treat ^ and $ as only matching at beginning and end of text.

matches alternation of Subs.

matches any character.

matches any character except newline.

matches empty string at beginning of line.

matches empty string at beginning of text.

capturing subexpression with index Cap, optional name Name.

matches Runes interpreted as range pair list.

matches concatenation of Subs.

matches empty string.

matches empty string at end of line.

matches empty string at end of text.

matches Runes sequence.

matches no strings.

matches word non-boundary `\B`.

matches Sub[0] one or more times.

matches Sub[0] zero or one times.

matches Sub[0] at least Min times, at most Max (Max == -1 is no limit).

matches Sub[0] zero or more times.

matches word boundary `\b`.

as close to Perl as possible.

allow Perl extensions.

POSIX syntax.

regexp contains no counted repetition.

allow \p{Han}, \P{Han} for Unicode group and negation.

regexp OpEndText was $, not \z.

An Error describes a failure to parse a regular expression and gives the offending expression.

An Inst is a single instruction in a regular expression program.

A Prog is a compiled regular expression program.

A Regexp is a node in a regular expression syntax tree.

An EmptyOp specifies a kind or mixture of zero-width assertions.

An ErrorCode describes a failure to parse a regular expression.

Flags control the behavior of the parser and record information about regexp context.

An InstOp is an instruction opcode.

An Op is a single regular expression operator.