Function concat

index/regexp.go:558–597

concat returns the regexp info for xy given x and y.

(x, y regexpInfo)

// concat returns the regexp info for xy given x and y.
func concat(x, y regexpInfo) (out regexpInfo) {
	//println("concat", x.String(), "...", y.String())
	//defer func() { println("->", out.String()) }()
	var xy regexpInfo
	xy.match = x.match.and(y.match)
	if x.exact.have() && y.exact.have() {
		xy.exact = x.exact.cross(y.exact, false)
	} else {
		if x.exact.have() {
			xy.prefix = x.exact.cross(y.prefix, false)
		} else {
			xy.prefix = x.prefix
			if x.canEmpty {
				xy.prefix = xy.prefix.union(y.prefix, false)
			}
		}
		if y.exact.have() {
			xy.suffix = x.suffix.cross(y.exact, true)
		} else {
			xy.suffix = y.suffix
			if y.canEmpty {
				xy.suffix = xy.suffix.union(x.suffix, true)
			}
		}
	}

	// If all the possible strings in the cross product of x.suffix
	// and y.prefix are long enough, then the trigram for one
	// of them must be present and would not necessarily be
	// accounted for in xy.prefix or xy.suffix yet.  Cut things off
	// at maxSet just to keep the sets manageable.
	if !x.exact.have() && !y.exact.have() &&
		x.suffix.size() <= maxSet && y.prefix.size() <= maxSet &&
		x.suffix.minLen()+y.prefix.minLen() >= 3 {
		xy.match = xy.match.andTrigrams(x.suffix.cross(y.prefix, false))
	}

	xy.simplify(false)
	return xy
}

// alternate returns the regexpInfo for x|y given x and y.
func alternate(x, y regexpInfo) (out regexpInfo) {