= Julia Type Hints =

Julia is a dynamically typed language, but '''type hints''' serve several purposes.

<<TableOfContents>>

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== Description ==

To provide the interpreter/compiler a type hint, try:

{{{
julia> (1+2)::Int
}}}

This acts as a type assertion: if the annotated value is not that type, then a type error is thrown.

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== Function Arguments ==

Try:

{{{
function foo(x::Int, y::Int)
    x + y
end
}}}

Best practice is to use [[Julia/DataTypes#Abstract_Types|abstract types]] on function arguments, so that novel subtypes found in packages can seamlessly work.

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== Struct Members ==

By default, [[Julia/DataTypes#Composite_Types|struct]] fields are typed as `Any`. Type hints can be applied to fields like:

{{{
julia> struct Foo
           bar
           baz::Int
           qux::Float64
       end

julia> foo = Foo("Hello, world.", 23, 1.5)
Foo("Hello, world.", 23, 1.5)
}}}

This causes values to be type cast, and potentially throw an error.

{{{
julia> Foo("Hello, world.", 23.5, 1)
ERROR: InexactError: Int64(23.5)
}}}



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