Where are the AST specs?
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Date:   (:) 
From:  Loup Vaillant <loup.vaillant@g...> 
Subject:  Re: [Camllist] Where are the AST specs? 
Here is the promised snipet of code. this is emacs lisp. One can evaluate these from the *scratch* buffer. (CxCe at the end of the expression). Of course, I assume here that '+' accept only two arguments, or else these macros are useless. (Actually, they are.) ; This macro is right associative (defmacro plus (first &rest tail) (if (null tail) first `(+ ,first (plus ,@tail)))) ; This one is left associative (defmacro sulp (first &rest tail) (if (null tail) first `(sulp (+ ,first ,(car tail)) ,@(cdr tail)))) ; some examples (plus 1 2 3 4 5) (sulp 1 2 3 4 5) I have not defined the macro definfing macros (I am no expert), yet I belive they do not take more than six lines each. Note that I will need read macros as well as regulars ones. That is the kind of power I want from Ocaml. If I succeed, I will consider solved (at least for my personnal usage) many syntax problems I read about in this list. 2007/3/19, Nicolas Pouillard <nicolas.pouillard@gmail.com>: > On 3/19/07, Loup Vaillant <loup.vaillant@gmail.com> wrote: > > 2007/3/19, Nicolas Pouillard <nicolas.pouillard@gmail.com>: > > > [...camlp4code...] > > > $ cat test_macros.ml > > > let cons x xs = x :: xs;; > > > > > > foldl(( + ), 1, 2, 3, 4);; > > > foldr(cons, 1, 2, 3, []);; > > > > > > $ camlp4o ./macros.cmo test_macros.ml > > > let cons x xs = x :: xs > > > let _ = ((1 + 2) + 3) + 4 > > > let _ = cons 1 (cons 2 (cons 3 [])) > > > > Impressive. > > If it is possible, It would be best would be to be able to write something like: > > (def_foldl + plus) > > > > and then just > > (+ x y z) > > (+ x y z w) > > ... > > The same for cons: > > (def_foldr :: cons) > > > > (:: x y z L) > > (:: x y z t []) > > $ cat macros.ml > open Camlp4.PreCast;; > let foldr_funs = ref [];; > let foldl_funs = ref [];; > AstFilters.register_str_item_filter begin > Ast.map_expr begin function >  <:expr@loc< def_foldr $lid:name$ $e$ >> > > foldr_funs := (name, e) :: !foldr_funs; <:expr@loc<()>> >  <:expr@loc< def_foldl $lid:name$ $e$ >> > > foldl_funs := (name, e) :: !foldl_funs; <:expr@loc<()>> >  e > e > end > end#str_item;; > AstFilters.register_str_item_filter begin > Ast.map_expr begin function >  <:expr@loc< $lid:name$($tup:e$) >> when List.mem_assoc name !foldl_funs > > let op = List.assoc name !foldl_funs in > let rec foldl = > function >  [] > assert false >  [x] > x >  x :: xs > <:expr@loc< $op$ $foldl xs$ $x$ >> > in foldl (List.rev (Ast.list_of_expr e [])) >  <:expr@loc< $lid:name$($tup:e$) >> when List.mem_assoc name !foldr_funs > > let op = List.assoc name !foldr_funs in > let rec foldr = > function >  [] > assert false >  [x] > x >  x :: xs > <:expr@loc< $op$ $x$ $foldr xs$ >> > in foldr (Ast.list_of_expr e []) >  e > e > end > end#str_item;; > > $ cat test_macros.ml > let cons x xs = x :: xs;; > > def_foldl ( !+ ) ( + );; > def_foldr ( !:: ) cons;; > > !+ (1, 2, 3, 4);; > !:: (1, 2, 3, []);; > > $ camlp4of ./macros.cmo test_macros.ml > let cons x xs = x :: xs > let _ = () > let _ = () > let _ = ((1 + 2) + 3) + 4 > let _ = cons 1 (cons 2 (cons 3 [])) > > > > What's wrong with the current anti quotation system? > > Err, actually, nothing... I just found the '$' ugly. But it is one > > character, and I may as well use it "as is". > > I don't like the sacrifice of $ for that purpose but that's just a > matter of taste. > >  > Nicolas Pouillard >