# Composite type comparison

**URL:** <https://discourse.julialang.org/t/composite-type-comparison/108192>\
**Category:** General Usage\
**Tags:** parametric-types\
**Created:** [December 30, 2023, 6:10pm UTC](https://discourse.julialang.org/t/composite-type-comparison/108192 "2023-12-30T18:10:22Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![jules](https://avatars.discourse-cdn.com/v4/letter/j/41988e/32.png) [@jules](https://discourse.julialang.org/u/jules)\
**Post date:** [December 30, 2023, 7:20pm UTC](https://discourse.julialang.org/t/composite-type-comparison/108192/2 "2023-12-30T19:20:58Z")

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Does this help?

> [@Why \[1, 2, 3\] is not a Vector{Number}?](https://discourse.julialang.org/t/why-1-2-3-is-not-a-vector-number/52645/3):
>
> Just to extract some relevant points because the manual is quite dense: Vector{Number} is a concrete type, and [1, 2, 3] has type Vector{Int}, which is also a concrete type. One concrete type is never a subtype of another concrete type, they are the leaves of the type tree. Vector{Number} is concrete, even though Number is not a concrete type. That’s because it has a concrete implementation which can store all types that are subtypes of Number, it has a specific memory layout etc. On the other…

In addition, the Tuple type is the only type which is covariant, which means that a Tuple is subtype of another Tuple if each of its element types is a subtype of the corresponding element type in the supertype Tuple.

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