[MacPorts] #15712: Add versions to platforms

[MacPorts]

#15712: Add versions to platforms
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  Reporter:  raimue       |      Owner:  larryv
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:  MacPorts 2.6.0
 Component:  base         |    Version:
Resolution:               |   Keywords:
      Port:               |
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Comment (by pmetzger):

 Side note: The OCaml OPAM people have a pretty rich language for
 specifying versions for platforms and dependencies. I'm not sure their
 syntax is worth stealing, but the ability to say things like "this
 requires a dependent package or platform not less than X in version and
 not greater than Y" is kind of cool. (When I work with opam, I long for
 many things that are built in to macports, and when I work with macports,
 I long for things built in to opam. opam's ability to specify versioning
 nicely is such a feature.)

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Ticket URL: <https://trac.macports.org/ticket/15712#comment:24>
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