NUMBER-SUBTREES.html -- ACL2 Version 6.3

## NUMBER-SUBTREES

`(number-subtrees x)` returns the number of distinct subtrees of X, in the `` sense of `equal`

    Major Section:  HONS-AND-MEMOIZATION

This documentation topic relates to the experimental extension of ACL2 supporting hash cons, fast alists, and memoization; see hons-and-memoization.

In the logic, `number-subtrees` is defined as the length of `cons-subtrees`.

Under the hood, we first `hons-copy` X to obtain a normed version, then count the number of unique conses in X using an EQ hash table.