CVS difference for ais/ai-00173.txt

Differences between 1.1 and version 1.2
Log of other versions for file ais/ai-00173.txt

--- ais/ai-00173.txt	1998/09/30 00:17:32	1.1
+++ ais/ai-00173.txt	1998/10/01 03:20:20	1.2
@@ -761,3 +761,46 @@
 optimization and type safety concerns from the meeting.
 
 ****************************************************************
+
+From: 	Norman H Cohen[SMTP:ncohen@us.ibm.com]
+Sent: 	Thursday, April 30, 1998 12:58 PM
+
+The discussion of AI-173 omits the Venn diagram that Tuck drew, which I think
+is the key to the solution.  Here is the same hierarchy, presented as a tree:
+
+Address-taken objects
+(includes subtrees below +
+ X for which X'Address is written locally)
+   |
+   +---------aliased objects of type T1
+   |         (includes subtrees below+
+   |          declared aliased+
+   |          designated by general access types)
+   |             |
+   |             +-----objects of type T1 designated
+   |             |        by pool-specific type A11
+   |             |
+   |             +-----objects of type T1 designated
+   |                      by pool-specific type A12
+   |
+   +---------aliased objects of type T2
+             (includes subtrees below+
+              declared aliased+
+              designated by general access types)
+                 |
+                 +-----objects of type T2 designated
+                 |        by pool-specific type A21
+                 |
+                 +-----objects of type T2 designated
+                           by pool-specific type A22
+
+Suppose each object is placed in the innermost applicable Venn-diagram circle,
+or the applicable tree node farthest from the root.  Then assignment to a
+variable in a given category should force the compiler to regard all objects
+placed in the same category, in enclosing categories, and in enclosed
+categories to be regarded as potentially modified.  (In the AI, of course, I
+have to word that from the point of view of the programmer rather than the
+compiler.)
+
+-- Norman
+****************************************************************

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