;; TO DO:
;;
-;; (apply (lambda (x &rest y) ...) 1 (foo))
-;;
-;; maintain a list of functions known not to access any global variables
-;; (actually, give them a 'dynamically-safe property) and then
-;; (let ( v1 v2 ... vM vN ) <...dynamically-safe...> ) ==>
-;; (let ( v1 v2 ... vM ) vN <...dynamically-safe...> )
-;; by recursing on this, we might be able to eliminate the entire let.
-;; However certain variables should never have their bindings optimized
-;; away, because they affect everything.
-;; (put 'debug-on-error 'binding-is-magic t)
-;; (put 'debug-on-abort 'binding-is-magic t)
-;; (put 'debug-on-next-call 'binding-is-magic t)
-;; (put 'inhibit-quit 'binding-is-magic t)
-;; (put 'quit-flag 'binding-is-magic t)
-;; (put 't 'binding-is-magic t)
-;; (put 'nil 'binding-is-magic t)
-;; possibly also
-;; (put 'gc-cons-threshold 'binding-is-magic t)
-;; (put 'track-mouse 'binding-is-magic t)
-;; others?
-;;
-;; Simple defsubsts often produce forms like
-;; (let ((v1 (f1)) (v2 (f2)) ...)
-;; (FN v1 v2 ...))
-;; It would be nice if we could optimize this to
-;; (FN (f1) (f2) ...)
-;; but we can't unless FN is dynamically-safe (it might be dynamically
-;; referring to the bindings that the lambda arglist established.)
-;; One of the uncountable lossages introduced by dynamic scope...
-;;
-;; Maybe there should be a control-structure that says "turn on
-;; fast-and-loose type-assumptive optimizations here." Then when
-;; we see a form like (car foo) we can from then on assume that
-;; the variable foo is of type cons, and optimize based on that.
-;; But, this won't win much because of (you guessed it) dynamic
-;; scope. Anything down the stack could change the value.
-;; (Another reason it doesn't work is that it is perfectly valid
-;; to call car with a null argument.) A better approach might
-;; be to allow type-specification of the form
-;; (put 'foo 'arg-types '(float (list integer) dynamic))
-;; (put 'foo 'result-type 'bool)
-;; It should be possible to have these types checked to a certain
-;; degree.
-;;
-;; collapse common subexpressions
-;;
-;; It would be nice if redundant sequences could be factored out as well,
-;; when they are known to have no side-effects:
-;; (list (+ a b c) (+ a b c)) --> a b add c add dup list-2
-;; but beware of traps like
-;; (cons (list x y) (list x y))
-;;
-;; Tail-recursion elimination is not really possible in Emacs Lisp.
-;; Tail-recursion elimination is almost always impossible when all variables
-;; have dynamic scope, but given that the "return" byteop requires the
-;; binding stack to be empty (rather than emptying it itself), there can be
-;; no truly tail-recursive Emacs Lisp functions that take any arguments or
-;; make any bindings.
-;;
-;; Here is an example of an Emacs Lisp function which could safely be
-;; byte-compiled tail-recursively:
-;;
-;; (defun tail-map (fn list)
-;; (cond (list
-;; (funcall fn (car list))
-;; (tail-map fn (cdr list)))))
-;;
-;; However, if there was even a single let-binding around the COND,
-;; it could not be byte-compiled, because there would be an "unbind"
-;; byte-op between the final "call" and "return." Adding a
-;; Bunbind_all byteop would fix this.
-;;
-;; (defun foo (x y z) ... (foo a b c))
-;; ... (const foo) (varref a) (varref b) (varref c) (call 3) END: (return)
-;; ... (varref a) (varbind x) (varref b) (varbind y) (varref c) (varbind z) (goto 0) END: (unbind-all) (return)
-;; ... (varref a) (varset x) (varref b) (varset y) (varref c) (varset z) (goto 0) END: (return)
-;;
-;; this also can be considered tail recursion:
-;;
-;; ... (const foo) (varref a) (call 1) (goto X) ... X: (return)
-;; could generalize this by doing the optimization
-;; (goto X) ... X: (return) --> (return)
-;;
-;; But this doesn't solve all of the problems: although by doing tail-
-;; recursion elimination in this way, the call-stack does not grow, the
-;; binding-stack would grow with each recursive step, and would eventually
-;; overflow. I don't believe there is any way around this without lexical
-;; scope.
-;;
-;; Wouldn't it be nice if Emacs Lisp had lexical scope.
-;;
-;; Idea: the form (lexical-scope) in a file means that the file may be
-;; compiled lexically. This proclamation is file-local. Then, within
-;; that file, "let" would establish lexical bindings, and "let-dynamic"
-;; would do things the old way. (Or we could use CL "declare" forms.)
-;; We'd have to notice defvars and defconsts, since those variables should
-;; always be dynamic, and attempting to do a lexical binding of them
-;; should simply do a dynamic binding instead.
-;; But! We need to know about variables that were not necessarily defvared
-;; in the file being compiled (doing a boundp check isn't good enough.)
-;; Fdefvar() would have to be modified to add something to the plist.
-;;
-;; A major disadvantage of this scheme is that the interpreter and compiler
-;; would have different semantics for files compiled with (dynamic-scope).
-;; Since this would be a file-local optimization, there would be no way to
-;; modify the interpreter to obey this (unless the loader was hacked
-;; in some grody way, but that's a really bad idea.)
-
-;; Other things to consider:
-
-;; ;; Associative math should recognize subcalls to identical function:
-;; (disassemble (lambda (x) (+ (+ (foo) 1) (+ (bar) 2))))
-;; ;; This should generate the same as (1+ x) and (1- x)
-
-;; (disassemble (lambda (x) (cons (+ x 1) (- x 1))))
;; ;; An awful lot of functions always return a non-nil value. If they're
;; ;; error free also they may act as true-constants.
-
+;;
;; (disassemble (lambda (x) (and (point) (foo))))
+
;; ;; When
;; ;; - all but one arguments to a function are constant
;; ;; - the non-constant argument is an if-expression (cond-expression?)
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