Function parsePattern

pm/pm.go:380–456

(sc *scanner, toplevel bool)

}

func parsePattern(sc *scanner, toplevel bool) *seqPattern {
	pat := &seqPattern{}
	if toplevel {
		if sc.Peek() == '^' {
			sc.Next()
			pat.MustHead = true
		}
	}
	for {
		ch := sc.Peek()
		switch ch {
		case '%':
			sc.Save()
			sc.Next()
			switch sc.Peek() {
			case '0':
				panic(newError(sc.CurrentPos(), "invalid capture index"))
			case '1', '2', '3', '4', '5', '6', '7', '8', '9':
				pat.Patterns = append(pat.Patterns, &numberPattern{sc.Next() - 48})
			case 'b':
				sc.Next()
				pat.Patterns = append(pat.Patterns, &bracePattern{sc.Next(), sc.Next()})
			default:
				sc.Restore()
				pat.Patterns = append(pat.Patterns, &singlePattern{parseClass(sc, true)})
			}
		case '.', '[', ']':
			pat.Patterns = append(pat.Patterns, &singlePattern{parseClass(sc, true)})
		//case ']':
		//	panic(newError(sc.CurrentPos(), "invalid ']'"))
		case ')':
			if toplevel {
				panic(newError(sc.CurrentPos(), "invalid ')'"))
			}
			return pat
		case '(':
			sc.Next()
			if sc.Peek() == ')' {
				sc.Next()
				pat.Patterns = append(pat.Patterns, &posCapPattern{})
			} else {
				ret := &capPattern{parsePattern(sc, false)}
				if sc.Peek() != ')' {
					panic(newError(sc.CurrentPos(), "unfinished capture"))
				}
				sc.Next()
				pat.Patterns = append(pat.Patterns, ret)
			}
		case '*', '+', '-', '?':
			sc.Next()
			if len(pat.Patterns) > 0 {
				spat, ok := pat.Patterns[len(pat.Patterns)-1].(*singlePattern)
				if ok {
					pat.Patterns = pat.Patterns[0 : len(pat.Patterns)-1]
					pat.Patterns = append(pat.Patterns, &repeatPattern{ch, spat.Class})
					continue
				}
			}