Is Julia's way of OOP superior to C++/Python? Why Julia doesn't use class-based OOP?

Internals & Design
84

I try an keep a list of small clear cases where multiple dispatch is a undisputabled better solution

1. Structured Matrix Multiplication.

I have this written up full here, so can read that blog post (or watch the talk version which is at the top of the page)

2. Arithmetic Type Promotion

Turns out this is really hard.
A few years ago a large proposal to overhaul Swift’s Integer type was written.
Even in this large document, they explictly:

DOES NOT solve the integer promotion problem, which would allow mixed-type arithmetic. However, we believe that it is an important step in the right direction.

To understand type promotion and why it needs multiple dispatch consider;

  • +(::Int32, ::Float64)::Float64
  • +(::Float64, ::Int32)::Float64
  • +(::Complex{Int32}, ::Float64)::Complex{Float64}

The resulting type depends on both input types, and not in a trivial way either.

3. Contextual Formatting of Objects

IIRC @thautwarm said on twitter something like “The quality of a language can be determined by how hard it is to access polymorpic printing methods”
Which I took to mean this.

This applies to julias whole show(::IO, ::Mime, ::Object), but lets sep away from that to think about generating some document.

Lets consider that was have verious objects that need to be displayed:

  • Number
  • Text
  • Equation

And variouis contexts with in the document to display them:

  • FlowingContent
  • Diagram
  • Table

So consider the options:

  • Number in general should be shown using proportional figures
  • Numbers inside Tables should be shown with tabular figures
  • Anything in FlowingContent should be shown in serifed font
  • Anything in Diagrams should be shown in with a sanserifed font
  • Except Equations in Diagrams should be shown in large sized serifed font
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Why specify argument types and return types