[GHC] #15078: base: Customary type class laws (e.g. for Eq) and non-abiding instances (e.g. Float) should be documented

[GHC]

#15078: base: Customary type class laws (e.g. for Eq) and non-abiding instances
(e.g. Float) should be documented
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        Reporter:  sjakobi           |                Owner:  Azel
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Core Libraries    |              Version:  8.4.2
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4736
       Wiki Page:                    |
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Comment (by Azel):

 Thinking about it, I think `Fractional` instances are expected to form
 division rings, `Floating` instances are expected to form exponential
 fields and `signum` and `abs` could imply that `Num` instances are
 expected to be division rings as well but if so division ought to be
 there. `RealFloat` is for machine-level floating-point types so there
 shouldn't be anything to add rules-wise.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15078#comment:8>
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