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From: quale@picard.cs.wisc.edu (Douglas E. Quale)
Newsgroups: comp.lang.misc
Subject: Re: Run-time Type Errors in Smalltalk
Message-ID: <1991May16.153308.4054@spool.cs.wisc.edu>
Date: 16 May 91 15:33:08 GMT
References: <1991May13.082152.29294@tkou02.enet.dec.com> <1991May15.141839.20603@daffy.cs.wisc.edu> <1991May16.011804.21042@tkou02.enet.dec.com>
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In article <1991May16.011804.21042@tkou02.enet.dec.com> diamond@jit533.enet@tkou02.enet.dec.com (Norman Diamond) writes:
>
>typedef enum XtArgTag {
>        XtArgCaddr,
>        XtArgCharPtr,
>        XtArgLong,
>        XtArgIntPtr,
>        XtArgProcPtr,
>} XtArgTag;
>typedef union XtArgUnion {
>        caddr_t     Caddr;
>        char       *CharPtr;
>        long        Long;
>        int        *IntPtr;
>        proc       *ProcPtr;
>} XtArgUnion;
>typedef struct XtArgVal {
>        XtArgTag    Tag;
>        XtArgUnion  Val;
>} XtArgVal;
>

I think there are reasons why the X Toolkit Intrinsics doesn't do this.
One of the design goals was binary compatibility with past versions.

Notice that when you are forced to simulate dynamic typing in a statically
typed language you can't do it as well as a dynamically typed language can.
The explicit tags are bulky and slow compared to the representation tricks
used by lisp compilers.  Also the syntax is abominable, as you mentioned.

To boot, when (or in my case more likely if) I write my own widget and
introduce a new arg type I have to use Caddr, and type safety is shot to hell.
Dynamically typed languages are safer than primitive statically typed
languages such as C.

-- Doug Quale
quale@picard.cs.wisc.edu