CODEWITHSUNDEEP
julia
Oleh Devua
Oleh Devua

Reputation: 384

is it possible to get collection of types what form the union?

Let's say I have the Union:

    SomeUnion = Union{Int, String}

Is there a method to extract a collection of types that form this union? For example ....

    union_types(SomeUnion) # => [Int, String]

Upvotes: 7

Views: 976

Answers (3)

ederag
ederag

Reputation: 2509

Base.uniontypes is not documented (as of julia-1.6.1), so use with care. But it works:

julia> SomeUnion = Union{Int, String}
Union{Int64, String}

julia> Base.uniontypes(SomeUnion)
2-element Vector{Any}:
 Int64
 String

Upvotes: 2

tim
tim

Reputation: 2096

For Julia 0.6, NEWS.md states that "Union types have two fields, a and b, instead of a single types field". Additionally, "Parametric types with "unspecified" parameters, such as Array, are now represented as UnionAll types instead of DataTypes".

Thus, to get the types as a tuple, one can do

union_types(x::Union) = (x.a, union_types(x.b)...)
union_types(x::Type) = (x,)

If you want an array, just collect the tuple

julia> collect(union_types(Union{Int, Float64, String, Array}))
4-element Array{Type,1}:
 Int64  
 Float64
 String
 Array

Upvotes: 4

Gnimuc
Gnimuc

Reputation: 8566

just write down a simple example here:

a = Union(Int,String)

function union_types(x)
  return x.types
end

julia> union_types(a)
(Int64,String)

you can store the result into an array if you want:

function union_types(x)
    return collect(DataType, x.types)
end

julia> union_types(a)
2-element Array{DataType,1}:
 Int64 
 String

UPDATE: use collect as @Luc Danton suggested in comment below.

Upvotes: 3

Related Questions