Re: [Sbcl-devel] better constantp

[Nikodemus S. <tsi...@cc...>]

On Fri, 4 Nov 2005, James Y Knight wrote:

> So I'd like to make constantp return t more often, in particular, cases like

> It seems like the nicest way to do that may be to IR1-compile the argument, 
> and then check the IR1 output to see if it looks like a constant function.

Sounds like a shitload of work for CONSTANTP. ;-)

For testing the constantness of complex form I think an evaluator-like
approach might be better:

  1) macroexpand the form
  2) if a function call, is this function foldable?
  3) if foldable, are all the arguments constant?

Much less work then compiling the form, and arguably cleaner too.

Cheers,

  -- Nikodemus              Schemer: "Buddha is small, clean, and serious."
                   Lispnik: "Buddha is big, has hairy armpits, and laughs."