Another option that already works is to define this on \circ with a unicode modifier, i.e. ∘̂ (typed \circ<TAB>\hat<TAB>):
julia> ∘̂(f, g) = g ∘ f
∘̂ (generic function with 1 method)
julia> (sin ∘̂ cos)(1)
julia> (cos ∘ sin)(1)
"∘̂" can be typed by \circ<tab>\hat<tab>
No documentation found.
∘̂ is a Function.
# 1 method for generic function "∘̂":
 ∘̂(f, g) in Main at REPL:1
In https://github.com/JuliaLang/julia/pull/34722 I added \fatsemi<TAB> completion. But I just realized that ⨟ almost looks like the “blackboard font” version of ; so maybe \bb;<TAB> (like \bbX<TAB> expands to 𝕏) also makes sense?
My misunderstanding. Thanks for pointing out that it is actually the same symbol (which unicode version or whether both will be best decided in the pullrequest).
For better autocompletion \fatsemi is very nice to have. For those who know the \bb family, I guess that one is more self-explanatory (haven’t used that so far). Would go with both or if only one is required, prefer \fatsemi