If I understand you correctly, it is possible to see such an optimization in Racket? It would be awesome to use this style to control the loops.
28.06.10, 23:47, "Matthias Felleisen" <matth...@ccs.neu.edu>: > > I pointed out Jinx's paper to Matthew last week. > > Not surprisingly, reality and theory never match with the MIT Scheme > compiler. > > > On Jun 28, 2010, at 3:04 PM, Joe Marshall wrote: > > > On Fri, Jun 25, 2010 at 11:50 AM, Matthew Flatt > > wrote: > >> > >> Compilers can't easily see through a Y combinator, and a factor of > >> 8 or > >> so difference is probably typical for Lisp compilers. (I tried Ikarus > >> and Gambit to double check, and performance was about the same as > >> with > >> Racket.) > > > > See > > @INPROCEEDINGS{Juan92tamingthe, > > author = {Guillermo Juan and Guillermo Juan Rozas}, > > title = {Taming the Y operator}, > > booktitle = {In ACM Conference on LISP and Functional Programming}, > > year = {1992}, > > pages = {226--234}, > > publisher = {ACM Press} > > } > > ``In this paper I present a set of conceptually simple but involved > > techniques used by Liar 1 , the MIT Scheme compiler, to generate good > > code when recursive procedures are specified in terms of suitable > > versions of the Y operator. The techniques presented are > > general-purpose analysis and optimization tools, similar to well-known > > techniques used in the analysis and optimization of applicative > > languages, that combine synergistically to enable Liar to generate > > identical machine code for ordinary recursive definitions written > > using letrec and those written using suitable forms of Y.'' > > > > ;; Allow compiler to inline standard procedures. > > (declare (usual-integrations)) > > > > (define-syntax U > > (syntax-rules () > > ((_ f) (f f)))) > > > > (define-syntax define/comb > > (syntax-rules () > > ((_ comb name (arg1 arg2) body) > > (define name > > (comb (lambda (name) (lambda (arg1 arg2) body))))))) > > > > ;; Allow compiler to inline Z > > (define-integrable (Z f) > > (U (lambda (g) (lambda (x y) ((f (U g)) x y))))) > > > > (define/comb Z comb-sum (l t) > > (if (null? l) t (comb-sum (cdr l) (+ t (car l))))) > > > > (define (sum l t) > > (if (null? l) t (sum (cdr l) (+ t (car l))))) > > > > (define (test1) > > (let ((start-time (runtime)) > > (l (make-list 10000000 1))) > > (let ((answer (comb-sum l 0))) > > (- (runtime) start-time)))) > > > > (define (test2) > > (let ((start-time (runtime)) > > (l (make-list 10000000 1))) > > (let ((answer (sum l 0))) > > (- (runtime) start-time)))) > > > > (test1) => .11 seconds > > (test2) => .11 seconds > > > > > > -- > > ~jrm > > _________________________________________________ > > For list-related administrative tasks: > > http://lists.racket-lang.org/listinfo/users > > > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users