# Sound use of multiple dispatch?

**URL:** https://discourse.julialang.org/t/sound-use-of-multiple-dispatch/114093
**Category:** Performance
**Tags:** question
**Created:** [May 10, 2024, 10:07am UTC](https://discourse.julialang.org/t/sound-use-of-multiple-dispatch/114093 "2024-05-10T10:07:56Z")
**Posts on this page:** 1
**Showing post:** 8

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### Author: ![lmiq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/lmiq/32/18314_2.png) [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [May 10, 2024, 12:21pm UTC](https://discourse.julialang.org/t/sound-use-of-multiple-dispatch/114093/8 "2024-05-10T12:21:46Z")

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> [@Domenico\_Lahaye](#):
>
> I am not sure how to distinguish between less clean and more clean here. Could you pls. elaborate?

The point is: is you function `genmesh` _always_ requiring from the user the definition of `a` and `b` points?

If the answer is _yes_, than you can dispatch on the type of those points:

```julia-repl
julia> struct Point1D{T} <: FieldVector{1,T}
           x::T
       end

julia> struct Point2D{T} <: FieldVector{2,T}
           x::T
           y::T
       end

julia> genmesh(N::Int, a::Point1D, b::Point1D) = "1D mesh!"
genmesh (generic function with 1 method)

julia> genmesh(N::Int, a::Point2D, b::Point2D) = "2D mesh!"
genmesh (generic function with 2 methods)

julia> a = Point1D(0.0); b = Point1D(1.0);

julia> genmesh(100, a, b)
"1D mesh!"

julia> a = Point2D(0.0, 0.0); b = Point2D(1.0, 1.0);

julia> genmesh(100, a, b)
"2D mesh!"

```

but if, as in your example, you have default values for these `a`, and `b` parameters, and providing them explicitly is optional, there is no way for dispatch to know if the user wants a 1D or 2D mesh, if it can provide _only_ the number of points. Thus, then, you need to provide the dimension somehow. One way is to define two functions, `genmesh1D`, `genmesh2D`, other way is to provide two methods but require as a parameter the type of point (dimension) you want, which is what I did there.

Cleaner or not is something that you have to choose from a user point of view, in this case.

---

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