## GENERALIZE

make a rule to restrict generalizations
```Major Section:  RULE-CLASSES
```

See rule-classes for a general discussion of rule classes, including how they are used to build rules from formulas and a discussion of the various keywords in a rule class description.

```Example:
(defthm integer-listp-rev
(implies (integer-listp x)
(integer-listp (rev x)))
:rule-classes :generalize)

General Form:
any theorem
```
To use a `:generalize` rule, the system waits until it has decided to generalize some term, `term`, by replacing it with some new variable `v`. If any `:generalize` formula can be instantiated so that some non-variable subterm becomes `term`, then that instance of the formula is added as a hypothesis. Thus for the example above, if the term `(rev x2)` is generalized to the variable `rv` during a proof, then the following is added as a hypothesis when generalizing to a new goal.
```(implies (integer-listp x2)
(integer-listp rv))
```

At the moment, the best description of how ACL2 `:generalize` rules are used may be found in the discussion of ``Generalize Rules,'' page 248 of A Computational Logic Handbook, or ``Generalization,'' page 132 of ``Computer-Aided Reasoning: An Approach.'' Also see introduction-to-the-theorem-prover for detailed tutorial on using ACL2 to prove theorems, which includes some discussion of generalization.