RE: Checking if a function is built-in

[Drew Adams]

> > > Is there a predicate that can check if a function is built-in?
> >
> > subrp
> 
> I thought this was the way to use it (subrp 'cons)
> but it returns nil even though cons is a built-in function.
> Have I missed something?

(subrp (symbol-function 'cons))

`cons' is just a symbol. What you want to test is the function that the symbol
refers to. 

This is not the value of the symbol but the value of its function cell, which is
a function (a subr, in this case).