Type Unstable: Function within a Struct

New to Julia
1

I want to add a Function inside a Struct, Because I will read from a user provided CSV file that tell me what function to use.

In below example, I had a “sound” function inside each struct, that can perform different operations.
However, when I do “code_warntype”, I can clearly see Type unstable when reaching the function part.

abstract type Operate end
 
struct Cut <: Operate
    member::String
    sound::Function
end
Cut() = Cut("t", sum)
 
struct Push <: Operate
    member::Int
    sound::Function
end
Push() = Push(1, mean)
 
struct Roll <: Operate
    member::Symbol
    sound::Function
end
Roll() = Roll(:a, max)

a = Roll()
b = Push()
c = Cut()

function test(a::Operate)
    arr = [1,2,3,4,5]
    b = a.sound(arr)
    println(b)
end

@code_warntype test(a)
@code_warntype test(b)
@code_warntype test(c)

code_warntype:

8 ─ %23 = (Base.getfield)(a, :sound)::Function
│   %24 = (%23)(%2)::Any
│   %25 = (Main.println)(%24)::Any
└──       return %25

How to make the Function inside the Struct Type-stable?

2

Every function has its own type (Function is an abstract type), so you want to parameterize your struct by that type. Something like

struct Cut{F}
  member::String
  sound::F
end
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