Home     |     .Net Programming    |     cSharp Home    |     Sql Server Home    |     Javascript / Client Side Development     |     Ajax Programming

Ruby on Rails Development     |     Perl Programming     |     C Programming Language     |     C++ Programming     |     IT Jobs

Python Programming Language     |     Laptop Suggestions?    |     TCL Scripting     |     Fortran Programming     |     Scheme Programming Language


 
 
Cervo Technologies
The Right Source to Outsource

MS Dynamics CRM 3.0

Scheme Programming Language

Is it possible to define-syntax "define-struct" ?


hi

Is it possible to define-syntax "define-struct" ?
Mit scheme don't have mzscheme type define-struct.
thanks

On Mar 29, 2:08 am, "maina@gmail.com" <maina@gmail.com> wrote:

> Is it possible to define-syntax "define-struct" ?

Do you mean the "define-struct" like the one described in the
following URL?
  http://pre.plt-scheme.org/docs/html/beginning/define-struct.html

To do that, you need two things:
1. A suitable representation for the struct types.
2. A macro system.

> Mit scheme don't have mzscheme type define-struct.

I don't know much about MIT Scheme but here is the general idea.

If your Scheme system provides the means for creating new record/
struct types, then you can use that as a basis for the representation
of your structs.  Otherwise, tagged vectors (i.e. vectors where the
first element is a descriptor for the struct type) may work ok.

If your want "define-struct" to construct the constructor, predicate,
accessors and setters names for you, then you need a macro system that
has that capability.  A syntax-case system would work nicely.  If all
you have is syntax-rules, then you need to specify the names of all
the procedures in the define-struct form.  This would make define-
struct forms look something like:

(define-struct foo make-foo foo?
  (foo-bar set-foo-bar!)
  (foo-baz set-foo-baz!)
  ...)

instead of the much shorter form:

(define-struct foo (bar baz ...))

Does this answer your question?  Let us know if you have any troubles.

Aziz,,,

On Mar 29, 2:40 pm, "Abdulaziz Ghuloum" <aghul@gmail.com> wrote:

Mit scheme don't have any define-struct.
Do you know what's the last field "#f" mean in "(define-struct term
(tag exprs) #f)"? the default value? Thanks.
I will think about how to get around this.

maina@gmail.com writes:
> Mit scheme don't have any define-struct.

When I put to Google the three words "mit scheme record", I get back
this:

# MIT Scheme provides a record abstraction, which is a simple and
# flexible mechanism for building structures with named
# components. Records can be defined and ...

It may be just referring to the same thing with a different name.
Look for records.

On Mar 29, 12:08 am, "maina@gmail.com" <maina@gmail.com> wrote:
> hi

> Is it possible to define-syntax "define-struct" ?
> Mit scheme don't have mzscheme type define-struct.
> thanks

Teach yourself scheme in fixnum days shows a macro for define-struct,
but it uses define-macro/defmacro instead of define-syntax. I don't
know if MIT supports that.

Brad

Another approach addressed here:
http://okmij.org/ftp/Scheme/define-struct.html

Basically, with plt/chez <<use define-record in chez>> (define-struct
FOO ...) defines 3+ procedures: make-FOO, FOO-fieldname (1 for each
field) and FOO?. The above link describes a syntax for define-struct in
which (define-struct FOO ...) creates a new syntax FOO which works like
this:
(FOO make ...)
(FOO fieldname ...)
(FOO ? ...)

The (FOO ...) form is then expanded to the proper procedure based on the
first argument (using the term "argument" loosely).

regards,

Nate T.

Add to del.icio.us | Digg this | Stumble it | Powered by Megasolutions Inc