Procedure qualifiers

[shirok]

define-cproc allows some qualifiers for defined subrs, notably :constant. It sets constant flag of <procedure> and allows the compile to perform constant folding.

We don't have a corresponding mechanism for Scheme-defined procedures.

Syntax-wise, we can allow meta-info between formals and body, e.g. (lambda (x y ..) :constant body ...). How to carry over that information within IForm needs some cleverness. That meta info needs to be saved in the packed IForm.

We have flags slot in $LAMBDA node. It has already been used in non-extensible way. We may change it to contain, say, a list of symbols and/or packed IForm. We still need to recognize the old form, for the precompiled code may contain the old form.

[lassik]

Common Lisp uses

(lambda (x y ...)
  (declare constant)
  ...)

[lassik]

It would be generally useful to have (declare ...) in Scheme eventually, as well as CL style procedure docstrings.

CLHS:

• 3.3 Declarations
• 3.4.11 Syntactic Interaction of Documentation Strings and Declarations

[shirok]

Good idea. It's flexible.

I do intend, though, to introduce optional type declaration, and although using (declare ...) form is within the boundary of Scheme, I'm inclined to explore syntactic extension to visually indicate it's a meta information.