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Type of union of disjunct functions?


Where's the contravariance?Are there type signatures which Haskell can't verify?Type theory: type kindsDoes C++11 support types recursion in templates?One type vs. multiple typesRepresenting a fixpoint in a head-normal lambda calculus ASTWhat's the difference between parametric polymorphism and higher-kinded types?Proving commutativity of type level addition of natural numbersA category of type-changing substitutionsWhat is positivity checking?






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2















Given two functions:



f :: EvenInteger -> 0
g :: OddInteger -> 1


consider the function



h = (x :: Integer) => 
if(x is even)return f(x);
return g(x);




What the smallest type T such that



h :: T


I was thinking that it is simply



h :: (typeof f) & (typeof g)


But then I would also think that a function call distributes over conjunction i.e., that



x :: EvenInteger
h(x) :: (typeof f(x)) & (typeof g(x))


which begs another question:



What is



(OddInteger -> 1)(EvenInteger)









share|improve this question






























    2















    Given two functions:



    f :: EvenInteger -> 0
    g :: OddInteger -> 1


    consider the function



    h = (x :: Integer) => 
    if(x is even)return f(x);
    return g(x);




    What the smallest type T such that



    h :: T


    I was thinking that it is simply



    h :: (typeof f) & (typeof g)


    But then I would also think that a function call distributes over conjunction i.e., that



    x :: EvenInteger
    h(x) :: (typeof f(x)) & (typeof g(x))


    which begs another question:



    What is



    (OddInteger -> 1)(EvenInteger)









    share|improve this question


























      2












      2








      2








      Given two functions:



      f :: EvenInteger -> 0
      g :: OddInteger -> 1


      consider the function



      h = (x :: Integer) => 
      if(x is even)return f(x);
      return g(x);




      What the smallest type T such that



      h :: T


      I was thinking that it is simply



      h :: (typeof f) & (typeof g)


      But then I would also think that a function call distributes over conjunction i.e., that



      x :: EvenInteger
      h(x) :: (typeof f(x)) & (typeof g(x))


      which begs another question:



      What is



      (OddInteger -> 1)(EvenInteger)









      share|improve this question
















      Given two functions:



      f :: EvenInteger -> 0
      g :: OddInteger -> 1


      consider the function



      h = (x :: Integer) => 
      if(x is even)return f(x);
      return g(x);




      What the smallest type T such that



      h :: T


      I was thinking that it is simply



      h :: (typeof f) & (typeof g)


      But then I would also think that a function call distributes over conjunction i.e., that



      x :: EvenInteger
      h(x) :: (typeof f(x)) & (typeof g(x))


      which begs another question:



      What is



      (OddInteger -> 1)(EvenInteger)






      type-theory






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Mar 23 at 21:44









      Ray Toal

      68k11128185




      68k11128185










      asked Mar 23 at 21:39









      AdamAdam

      1,067314




      1,067314






















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