- This message is generated when a pattern is encountered on the right-hand side of a rule.
- This is a warning message about an unusual use of patterns. It does not necessarily indicate an error.
- A pattern is an expression that matches something other than itself. x_ and p__ are examples of common patterns.
- Patterns are typically used only on the left-hand sides of rules and assignments.
- Off[message] switches off the message; On[message] switches it on. For example: Off[Rule::rhs].