Re: Issue: ARRAY-TYPE-ELEMENT-TYPE-SEMANTICS (Version 9)

[Kent M Pitman <KMP@STONY-BROOK.SCRC.Symbolics.COM>]

    Date: 11 Jan 89 21:34 PST
    From: masinter.pa@Xerox.COM

    ... You can implement (C:TYPEP object type) by (if (simple-small-p object)
    (b:typep object type) (a:typep object type)). I.e., TYPEP need not merely
    be implemented by ARRAYP + a test on ARRAY-ELEMENT-TYPE. 

Larry, I started off sympathetic to your point of view. The same idea
had occurred to me. But how would you implement SUBTYPEP? The problem is
that you'd have to always specify the range just in case it mattered.
Although it precludes some interesting special-purpose representation, I
take it as a pragmatic truth, independently of what I might wish, that
we can't really make this proposal work unless implementations agree to
make the upgrading depend only on the requested type and nothing else.