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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!aoa!mark
From: mark@aoa.UUCP (Som Hane)
Newsgroups: comp.lang.ada
Subject: Re: Dynamic Typing in Ada
Summary: I think you have missed the point
Keywords: DYNAMIC
Message-ID: <730@aoa.UUCP>
Date: 19 Mar 89 21:52:24 GMT
References: <8903101703.AA04518@ti.com>
Reply-To: mark@aoa.UUCP (Som Hane)
Distribution: usa
Organization: Adaptive Optics Assoc., Cambridge, Mass. USA
List-Id: <comp.lang.ada>

In article <8903101703.AA04518@ti.com> linnig@skvax1.csc.ti.com (Mike Linnig) writes:

>John Gateley's (Gateley@tilde.csc.ti.com) challenge was to implement the
>following lisp construct in Ada...
>
> ----------------------------------------------------------------------
>-- Scheme                           CL
>-- (define print                    (defun print (x)
>--   (lambda (x)                      (typecase x
>--     (cond                            (integer 1)
>--       ((integer? x) 1)               (real 2)
>--       ((real? x) 2)                  (complex 3)
>--       ((complex? x) 3)               (vector 4)))
>--       ((vector? x) 4))))
> ----------------------------------------------------------------------
>package dynamic_types is
>
> [ Ada code deleted ]
>
>I think this answers John Gateley's (Gateley@tilde.csc.ti.com) dynamic
>typing challenge. I didn't understand the first challenge; if it involved
>something similar to The C Language construct allowing pointers to
>procedures (and calling them) that can be handled too.
>

Let me start off by saying that I am a Lisp ( and C ) programmer, and have
only been doing Ada for 1 year, so I may be totally off base, but... I
think you may have missed the point.  In the CL example above the type of
"x" could be set or changed dynamically;  in your Ada example it was ( and
had to be ? ) set at compile time.  In addition, in the CL example the range
of choices in the typecase itself could be modified dynamically to be the
members of an arbitrary set of types ( some of which could themselves have
been dynamically created ).  I do not see at all how your example can be
modified to do any of these things... so I think the challenge has not been
met.

	Mark Reynolds

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