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From: Joe Buck <Joe.Buck@synopsys.COM>
To: "Joseph S. Myers" <jsm@polyomino.org.uk>
Cc: Mark Mitchell <mark@codesourcery.com>, GCC List <gcc@gcc.gnu.org>
Subject: Re: IMA vs tree-ssa
Date: Tue, 09 Mar 2004 00:54:00 -0000	[thread overview]
Message-ID: <20040308165420.A25757@synopsys.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0403090043430.17920@digraph.polyomino.org.uk>; from jsm@polyomino.org.uk on Tue, Mar 09, 2004 at 12:48:58AM +0000


On Mon, 8 Mar 2004, Mark Mitchell wrote:

On Tue, Mar 09, 2004 at 12:48:58AM +0000, Joseph S. Myers wrote:
> > A type system with non-transitive type-equality breaks all the standard 
> > mathematical models for type theory.  (And, yes, I know the C type 
> > system is ugly, but most of it can actually be modeled in pretty 
> > conventional ways.)  The category-theoretician in me is befuddled by 
> > what a non-transitive type-equality model could possibly mean.
> 
> It's not type-equality, it's type-compatibility.  Equality of types also
> exists, and behaves transitively.
> 
> Most of the problem cases involve incomplete types; e.g., int[] is
> compatible with int[3] and int[5] which are not compatible with each
> other.

Such a relationship can still be transitive if there is a direction.
For example, we can have a transitive "is_a" relationship such that

    int[3] is_a int[]
    int[5] is_a int[]

but there is no is_a relationship between int[3] and int[5], or between
int[] and int[3] in the reverse direction.

  reply	other threads:[~2004-03-09  0:54 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-02-26 22:49 Dale Johannesen
2004-02-26 22:52 ` law
2004-02-26 23:12   ` Dale Johannesen
2004-02-26 23:20     ` Richard Henderson
2004-02-26 23:34     ` law
2004-02-26 23:47       ` Dale Johannesen
2004-02-26 23:57         ` law
2004-02-27  0:21           ` Dale Johannesen
2004-02-27  1:05             ` law
2004-02-27  7:26               ` Dale Johannesen
2004-02-27 18:44                 ` Dale Johannesen
2004-03-04 18:38                   ` Dale Johannesen
2004-03-08 22:32                     ` Mark Mitchell
2004-03-08 22:46                       ` Dale Johannesen
2004-03-08 22:49                         ` Mark Mitchell
2004-02-27  8:28             ` Richard Henderson
2004-02-26 23:20 ` Richard Henderson
2004-02-26 23:26   ` Dale Johannesen
2004-02-26 23:50   ` Geoff Keating
2004-02-27  9:08     ` Richard Henderson
2004-02-27 22:00     ` Neil Booth
2004-02-27 22:04       ` Geoff Keating
2004-02-27 22:08         ` Neil Booth
2004-03-08 22:29           ` Mark Mitchell
2004-03-08 23:07             ` Gabriel Dos Reis
2004-03-08 23:32               ` Joe Buck
2004-03-09  0:07                 ` Dale Johannesen
2004-03-09  0:17                   ` Joseph S. Myers
2004-03-09  0:34                   ` Mark Mitchell
2004-03-09  0:49                     ` Joseph S. Myers
2004-03-09  0:54                       ` Joe Buck [this message]
2004-03-09  1:37                       ` Mark Mitchell
2004-03-09  2:43                         ` Gabriel Dos Reis
2004-03-09  2:53                           ` Paul Jarc
2004-03-09  3:09                             ` Gabriel Dos Reis
2004-03-09  3:15                               ` Paul Jarc
2004-03-09  3:22                                 ` Gabriel Dos Reis
2004-03-09  9:39                         ` Joseph S. Myers
2004-03-09  9:59                           ` Mark Mitchell
2004-03-09 10:41                             ` Joseph S. Myers
2004-03-09 11:14                               ` Mark Mitchell
2004-03-09 11:54                                 ` Joseph S. Myers
2004-03-09 17:26                                   ` Mark Mitchell
2004-03-09 17:37                                     ` Joseph S. Myers
2004-03-09 17:46                                       ` Mark Mitchell
2004-03-09 14:00                               ` Gabriel Dos Reis
2004-03-09 21:17                               ` Matthias Benkmann
2004-04-02  0:35                   ` Geoff Keating
2004-04-02  0:53                     ` Dale Johannesen
2004-04-02 18:18                       ` Geoff Keating
2004-04-02 19:41                         ` Dale Johannesen
2004-04-03  1:17                           ` Geoff Keating
2004-03-08 23:43               ` Mark Mitchell

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