CODEWITHSUNDEEP
typesjulia
diego caples
diego caples

Reputation: 55

How to make Julia multiple dispatch hierarchy work on array contents

I want to have a function that takes in an array of numbers and does some operation on them. To do this, I created the function

function squarearray(numinarray::Vector{Number})
  numinarray[1]^2
end

But when I tried calling it with

print(squarearray(Vector([1.0])))

it caused an error:

ERROR: LoadError: MethodError: no method matching squarearray(::Vector{Float64})
Closest candidates are:
squarearray(::Vector{Number}) at ~/Programming/ai/structlearn.jl:7
squarearray(::AbstractVector{Number}) at ~/Programming/ai/structlearn.jl:7

Float64 is a subtype of Number, so why won't this work? I know I could specify in the function that it takes in in array of floats, but I also want the function to work on ints.

Thanks!

-Diego

Upvotes: 1

Views: 182

Answers (1)

Jonathan F.
Jonathan F.

Reputation: 563

The "Number" Type is Abstract. This means no data can be directly of type Number. However, as you pointed out, Number has concrete subtypes, such as Float64. If you change

numinarray::Vector{<:Number} #limits to only subtypes of Number

or

numinarray::Vector{Float64} #limits to Float64 type

or

numinarray::Vector #Does not limit inputs

You should avoid the problem.

Upvotes: 3

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