Julia: 0.6でのRationalの回帰を支援する

Julia 0.5の場合：

help?> Rational
search: Rational rationalize Irrational SerializationState permutations

  No documentation found.

  Summary:

  immutable Rational{T<:Integer} <: Real

  Fields:

  num :: T<:Integer
  den :: T<:Integer

ジュリア0.6にいる間

help?> Rational
search: Rational rationalize Irrational SerializationState Factorization

  No documentation found.

  Base.Rational is of type UnionAll.

  Summary:

  struct UnionAll <: Type{T}

  Fields:

  var  :: TypeVar
  body :: Any

0.6の詳細は間違っています：

julia> Rational <: UnionAll
false

julia> fieldnames(Rational)
2-element Array{Symbol,1}:
 :num
 :den