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From Claude Warren <cla...@xenei.com>
Subject of isomorphism and AdhocDatatypes
Date Tue, 25 Sep 2018 08:48:33 GMT
I have a case that I know falls under Don't Do That (DDT), but it got me
wondering.

Background:

We have created a custom data type that extends AdhocDatatype and provides
a data type for an enum.  The parse() and unparse() methods work as
expected.

I have a test case that managed to create 2 instances of the datatype (this
is the DDT part).  I will be spending this morning figuring out why we do
this and what the proper solution is.  But it got me thinking.

The isomorphic test fails on the enum data type based literals.  Looking at
the code, in BaseDatatype.java, it perfors Object.equals( datatype1,
datatype2 ) in the various equality checks.

Question:

Since the two datatype instances return the same enum, and the lexical form
of the two is the same, and there is no language specified, should they not
be considered equal?  Should the two graphs not be considered isomorphic?

If not can someone explain why?

Claude

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