The Contains(rule) constraint does a dfs in the program tree and stores all holes that can contain can contain the target rule.
Additionally, each non-uniform hole is also stored in that list, even if that hole does not contain the target rule. This is because the children of a non-uniform hole are not instantiated yet and could potentially hold a 2. Depending on the grammar, this is either possible or not. The constraint could check this property and ignore holes that can, by grammar definition, never expand to the target rule.
The
Contains(rule)constraint does a dfs in the program tree and stores allholesthat can contain can contain the targetrule.Additionally, each non-uniform hole is also stored in that list, even if that hole does not contain the target
rule. This is because the children of a non-uniform hole are not instantiated yet and could potentially hold a2. Depending on the grammar, this is either possible or not. The constraint could check this property and ignore holes that can, by grammar definition, never expand to the targetrule.