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https://issues.apache.org/jira/browse/PROTON-1138?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15168118#comment-15168118
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ASF subversion and git services commented on PROTON-1138:
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Commit c7f3f558511ed07b8972304a2ba7a69dfc6b6354 in qpid-proton's branch
refs/heads/master from [~aconway]
[ https://git-wip-us.apache.org/repos/asf?p=qpid-proton.git;h=c7f3f55 ]
PROTON-1138: Simplify comparable class, make comparable inheritance private.
Simplified the comparable class.
- comparable<T> is a private empty base class that exists only to instantiate
operator friends of T.
- comparable<T> is never used in any other way.
- for any compiler with even rudimentary empty-base-class support, this has 0
run-time overhead.
I did some research to try and eliminate inheritance entirely. There are 2 well
known approaches.
1. boost::operators uses exactly the approach above.
2. std::rel_ops uses unconstrained templates that match anything with op == or
< operator, we already agreed that approach is unsuitable for public API.
I tried type-trait approaches but could not find one that was better than the
above. IMO inheritance is the right fit: It has no run-time overhead, it is
easy to understand, and we *want* "is-a" inheritance semantics: if `object` is
comparable then sub-classes of `object` should be comparable. (That is the part
that is hard to achieve with type-traits. When I realized I was trying to
reinvent inheritance I decided to let go.)
> Assorted C++ API cleanups
> -------------------------
>
> Key: PROTON-1138
> URL: https://issues.apache.org/jira/browse/PROTON-1138
> Project: Qpid Proton
> Issue Type: Improvement
> Components: cpp-binding
> Affects Versions: 0.13.0
> Reporter: Justin Ross
> Assignee: Justin Ross
> Fix For: 0.13.0
>
>
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