]> Gaurav Chanda wrote: > Hello > > I am using the Polymorphic XML Parser (PXP) to parse XML documents. I have made 2 files : point.ml and point.mli, which contain simple class definitions. > > The file point.mli contains: > > open Pxp_yacc ; > open Pxp_document ; > open Pxp_types ; > > class type point_sig = > object > value mutable x : Pxp_document.node 'a; > end; > > class point : point_sig ; > > > The file point.ml contains: > > open Pxp_yacc ; > open Pxp_document ; > open Pxp_types ; > > class type point_sig = > object > value mutable x : Pxp_document.node 'a; > end ; > > value def = "<def></def>" ; > value def = parse_wfdocument_entity default_config (from_string def) default_spec ; > value defr = def#root ; > > class point:point_sig = > object > value mutable x = defr; > end; > > I get an error message while compilation. My compilation command is : > ocamlopt -pp "camlp4r pa_extend.cmo" -I +camlp4 -I Ty/ -I /usr/lib/ocaml/site-lib/netstring -I /usr/lib/ocaml/site-lib/pxp-engine -I /usr/lib/ocaml/site-lib/pxp-lex-iso88591/ -c point.mli point.ml > > > The error message is : > > File "point.ml", line 15, characters 8-67: > The class type > object > val mutable x : > ('a Pxp_document.node Pxp_document.extension as 'a) Pxp_document.node > end > is not matched by the class type point_sig > The class type > object > val mutable x : > ('a Pxp_document.node Pxp_document.extension as 'a) Pxp_document.node > end > is not matched by the class type > object > val mutable x : > ('a Pxp_document.node #Pxp_document.extension as 'a) Pxp_document.node > end [...] > > I am not being able to define PXP objects inside classes. Could you help me solve this problem ? Hi Garuav, (the following in classic syntax) the problem is that 'a Pxp_document.node is not the full type, because there is a constraint on the parameter of the class Pxp_document.node, and the compiler correctly augments the type such that it reads ('a Pxp_document.node #Pxp_document.extension as 'a) Pxp_document.node. However, defr has the type ('a Pxp_document.node Pxp_document.extension as 'a) Pxp_document.node, which is not the same. This is all the long error message wants to tell you. The solution is quite simple: Use the complete type instead of 'a Pxp_document.node, i.e. class type point_sig = object val mutable x : ('a Pxp_document.node Pxp_document.extension as 'a) Pxp_document.node end Sorry that the types of PXP are that complicated. ('a Pxp_document.node Pxp_document.extension as 'a) Pxp_document.node reflects the fact that nodes have extensions, and the extensions are recursively bound to their nodes. This is sometimes a bit unhandy. Gerd -- ------------------------------------------------------------ Gerd Stolpmann * Viktoriastr. 45 * 64293 Darmstadt * Germany gerd@gerd-stolpmann.de http://www.gerd-stolpmann.de ------------------------------------------------------------ ------------------- 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