Re: Distinguishing `consp` and `functionp`

[Stefan Monnier]

>> > Dunno.  SBCL's compiler is pretty good, it propagates types  and warns
>> > say, when using generic+ instead of must faster fixum+.
>> Knowing "this is a function" isn't terribly better than "this is
>> either a function or a cons cell starting with `lambda`": it will rarely
>> let you turn a generic+ into a fixnum+.
> Isn't knowing "this is a function" a prerequisite for proving e.g.
> "this is a function returning a fixnum"?

Maybe it's a prerequisite, but it's pretty damn far from sufficient: if
you're in a position to know that it returns a fixnum, then you
most likely won't need `funcall` to tell you that it's a function.

There are much lower hanging fruits.


        Stefan