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[Caml-list] infix precedence
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Date: | 2002-06-21 (17:54) |
From: | dengping zhu <zhudp@c...> |
Subject: | Re: [Caml-list] infix precedence |
Hi, Daniel, I have to raise some questions about infix declaration in camlp4 again. Now I defined some infix as follows: ------------------------------------ let add_infix lev op = EXTEND GLOBAL: Pcaml.expr; Pcaml.expr: LEVEL $lev$ [ [ x = SELF; $op$; y = SELF -> <:expr< $lid:op$ $x$ $y$ >> ] ]; END;; let _ = add_infix "*" ">>*" let _ = add_infix "<" "wth" let _ = add_infix "||" "|||" ------------------------------------ Then I have a following function: let f = number ||| literal '-' >>* number wth (fun x -> -x) (where number and literal are some function I defined before.) According to the infix definition above, this function should work as: let f = number ||| (literal '-' >>* number wth (fun x -> -x)) because the precedence of 'wth' is higher than that of '|||'. But, it turns out to evaluate as: let f = (number ||| literal '-' >>* number) wth (fun x -> -x) So, I have to add parenthesis so that it can work properly. Can you help me to figure out this problem because I want to get rid of the parenthesis so that my code is more readable? Thanks a lot! Dengping On Tue, 28 May 2002, dengping zhu wrote: >Hi, Daniel, it works very well. >Thanks a lot! > >Dengping > > > > >On Wed, 29 May 2002, Daniel de Rauglaudre wrote: > >>Hi, >> >>On Tue, May 28, 2002 at 02:48:42PM -0400, dengping zhu wrote: >>> >>> I tried camlp4 before. I got the example from the camlp4 tutorial and >>> modified a little bit. >> >>Your code cannot work: you are defining a new entry, you are not using >>the entry of OCaml expressions, which is Pcaml.expr. >> >> $ cat foo.ml >> let add_infix lev op = >> EXTEND >> GLOBAL: Pcaml.expr; >> Pcaml.expr: LEVEL $lev$ >> [ [ x = SELF; $op$; y = SELF -> <:expr< $lid:op$ $x$ $y$ >> ] ]; >> END;; >> $ ocaml >> Objective Caml version 3.04+11 (2002-05-16) >> >> # #load "camlp4o.cma";; >> Camlp4s Parsing version 3.04+11 >> >> # #load "pa_extend.cmo";; >> # #load "q_MLast.cmo";; >> # #use "foo.ml";; >> val add_infix : string -> string -> unit = <fun> >> >>Type: >> Grammar.Entry.print Pcaml.expr;; >>to see the current entry of expressions. >> >>The available levels are "top", "expr1", ":=", "||", "&&", "<", "^", >>"+", "*", "**", "unary minus", "apply", "label", ".", "~-", "simple". >>They are the one you can use as first parameter of add_infix: >> >> # add_infix "*" "op1";; >> >>If you type >> Grammar.Entry.print Pcaml.expr;; >>then you see that the rule with "op1" has been added in the level "*". >> >> # let op1 x y = x + y + 1;; >> Toplevel input: >> # let op1 x y = x + y + 1;; >> ^^^ >> Parse error: 'module' uppercase identifier expected after 'let' (in >> [str_item]) >> >>Normal, since "op1" is now a keyword. Mmmm... the normal form should be: >> let (op1) x y = x + y + 1;; >>But it does not work... this is a bug in Camlp4 that I am going to fix. >> >>A solution should be to define it before the "add_infix"... >> >>But, in the meantime, this works: >> # let \op1 x y = x + y + 1;; >> val op1 : int -> int -> int = <fun> >> # 3 op1 4;; >> - : int = 8 >> >>-- >>Daniel de RAUGLAUDRE >>daniel.de_rauglaudre@inria.fr >>http://cristal.inria.fr/~ddr/ >>------------------- >>To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr >>Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ >>Beginner's list: http://groups.yahoo.com/group/ocaml_beginners >> > >------------------- >To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr >Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ >Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners