Function firstThisPathComponent

compiler/optimizer/join.go:162–173

firstThisPathComponent returns the first component common to every dag.This.Path in e and a Boolean indicating whether such a common first component exists.

(e dag.Expr)

// firstThisPathComponent returns the first component common to every dag.This.Path
// in e and a Boolean indicating whether such a common first component exists.
func firstThisPathComponent(e dag.Expr) (prefix string, ok bool) {
	walkT(reflect.ValueOf(e), func(t dag.ThisExpr) dag.ThisExpr {
		if prefix == "" {
			prefix = t.Path[0]
			ok = true
		} else if prefix != t.Path[0] {
			ok = false
		}
		return t
	})
	return prefix, ok
}

// stripFirstThisPathComponent removes the first component of every dag.This.Path in e.
func stripFirstThisPathComponent(e dag.Expr) {