# A precise definition of what it means to be an instance of an abstract type

**URL:** <https://discourse.julialang.org/t/a-precise-definition-of-what-it-means-to-be-an-instance-of-an-abstract-type/57270>\
**Category:** New to Julia\
**Tags:** question\
**Created:** [March 16, 2021, 7:45am UTC](https://discourse.julialang.org/t/a-precise-definition-of-what-it-means-to-be-an-instance-of-an-abstract-type/57270 "2021-03-16T07:45:56Z")\
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**Author:** ![path-doc](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/path-doc/32/19183_2.png) [@path-doc](https://discourse.julialang.org/u/path-doc)\
**Post date:** [March 16, 2021, 10:08am UTC](https://discourse.julialang.org/t/a-precise-definition-of-what-it-means-to-be-an-instance-of-an-abstract-type/57270/7 "2021-03-16T10:08:00Z")

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> [@Benny](#):
>
> `Ptr{Float64}` is not an instance, of `Ptr` .

Well, if you are right, then the manual is wrong as it explicitly says that `Ptr{Float64}` is an instance of `Ptr`. But, personally, I agree with you on this point.

But regarding

> [@Benny](#):
>
> `Ptr{Float64}` is a subtype,

consider

```Julia
julia> supertypes(Ptr{Float64})
(Ptr{Float64}, Ref{Float64}, Any)

julia> subtypes(Ptr)
Type[]

```

As you can see, `Ptr` is not in there. Yes, I know it is according to `<:`, but as I point out in [another discourse](https://discourse.julialang.org/t/counterexamples-to-the-interpretation-means-is-a-subtype-of/57274/2), it is not at all clear that `<:` means “is a subtype” in the case of `Ptr`.

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