[GHC] #13038: implementation of Modus ponens and Modus tollens

[GHC]

#13038: implementation of Modus ponens and Modus tollens
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        Reporter:  vanto             |                Owner:  (none)
            Type:  feature request   |               Status:  infoneeded
        Priority:  normal            |            Milestone:
       Component:  libraries/base    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by AntC):

 Replying to [comment:10 vanto]:
 > Replying to [[span(style=color: #FF0000, AntC )]]:\\
 > Here is an example.\\

 Not needed: I understand how modus tollens works/how to use it. (And you
 can reasonably expect that anyone who replies to you would know.)

 > I point out that my idea is to insert the Modus Tollens inside the type
 > inference algorithm ...

 Then what is needed is an example of how type inference would work.

 > Modus Tollens is not specific to programming, it can be found in
 > electronic circuits.(We can build AND,OR,NAND Gates ...)\\

 In Boolean logic, we have a closed world: not(True) ==> False; not(False)
 ==> True.

 In type inference we don't have a closed world. Knowing that type `a0` is
 `not(a0 ~ Int)` or `not(Num a0)` doesn't help draw any conclusions about
 `a0`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13038#comment:11>
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