a compatible DEFINE-STRUCT implementation for SISC

As a first step in the port of SchemeUnit to SISC, I'm looking at
features of MzScheme that SchemeUnit uses, that I can easily and
conveniently implement in SISC.

SchemeUnit uses the subtype feature of MzScheme's DEFINE-STRUCT.
SchemeUnit also supplies a structure inspector; however, this does not
appear to be used by SchemeUnit itself.  All SchemeUnit unit tests
still pass in MzScheme when the structure inspector is removed.

SISC has a MzScheme compatible implementation of DEFINE-STRUCT
provided by its RECORD module, but SISC's implementation does not
include subtypes.

I've written an implementation of DEFINE-STRUCT for SISC which does
include subtypes.  While it doesn't implement structure inspectors,
a structure inspector may be specified (and will be ignored) for
compatibility with code written for MzScheme.

Structures created by this code are actually SISC classes.  Thus:

    (define-struct s (field1 field2))

defines "s" as an SISC class, and

    (define-struct (t s) (field3 field4 field5))

defines "t" as a subclass of "s".

Likewise, fields are implemented as class slots, and field
accessors and modifiers (S-FIELD2, SET-T-FIELD3!, etc.) are
implemented as generic procedures on the classes.

User-friendly error checking is not performed.


The code may be downloaded as a zip file from

    http://code.andrewwilcox.name/project/schemeunit-sisc-port/define-struct.zip

The code is also available within a GNU Arch project named

    code-1nkB91yrSd/a/[email protected]/dev--a--0

within the src/name/andrewwilcox/mzcompatible directory.

The GNU Arch archive is published at:

    http://code.andrewwilcox.name/2005

and may be accessed from GNU Arch with commands such as:

    tla register-archive http://code.andrewwilcox.name/2005
    tla get code-1nkB91yrSd/a/[email protected]/dev--a--0


The distribution contains code from SISC's record.scm, and so is
covered by SISC's copyright.

Code that I wrote is dedicated to the public domain.


I'll be on vacation next week, so it will probably be a couple of
weeks before I complete another step.

Andrew Wilcox


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