> For example:

>> (defstruct (vec (:conc-name nil) (:constructor vec (x y z)))
>>   (x 0.0 :type single-float)
>>   (y 0.0 :type single-float)
>>   (z 0.0 :type single-float))

> This is using about 2x the memory of what you'd expect for each
> instance, and doing an extra memory indirection for each slot access.
> Proper support for storing the floats "raw" in the struct was added in
> 0.9.2 by David Lichteblau.

> Another possible pitfall on older SBCLs (<0.8.21) is that they don't
> honor the compiler policy for code entered on the repl, but compile it
> with low speed, high debug/safety. If you've been pasting the code
> into the repl instead of LOADing it, performance would indeed be
> horrible.