Cactus can infer many thing automatically:
| Category | Can be inferred | Can be given explicitly |
|---|---|---|
| Types of nonterminals | by type inference | yes |
| Names of types | from names of nonterminals | yes |
| Names of data constructors | no | yes |
| Types of data constructors | from their use | yes |
| Keywords | from use in concrete syntax | yes |
| Abstract syntax | yes... | yes |