Re: [Maxima-discuss] (MEMBER ...) with literal symbol(s)

[Raymond Toy]

On 5/2/25 8:56 AM, David Scherfgen wrote:

eq is a single machine instruction in most Lisp implementations and is inlined, i.e. doesn't require a function call.

In contrast, eql is usually not inlined - it incurs the overhead of a function call and performs additional type checks if eq returns nil.

Some experiments with SBCL show a factor ~10 difference in performance between eq and eql.

Does it matter within Maxima? Maybe. member is called extremely often, and during a test suite run, it's the top #7 function where time is being spent.

Maxima basically uses member as a short way of writing:

(or (eq ...) (eq ...) ...)

I'd argue that in this long-form, if we know we're working with symbols, we would definitely use eq, not eql. So if we optimize for eq in long-form code, shouldn't we be just as deliberate when using member?

I'm not sure we are (were) actually really deliberate about using `eq` instead `eql`.  Some of the code is really,  really old.

But I have no issues with replacing appropriate calls to `member` with `memq` instead.  That makes it clearer we really do want `eq` and, if needed, we can supply a compiler macro to further optimize the calls, as needed.