# Type Unstable: Function within a Struct
**URL:** https://discourse.julialang.org/t/type-unstable-function-within-a-struct/31110
**Category:** New to Julia
**Created:** [November 15, 2019, 1:52am UTC](https://discourse.julialang.org/t/type-unstable-function-within-a-struct/31110 "2019-11-15T01:52:57Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Eric\_Chen](https://discourse.julialang.org/u/Eric_Chen)
#### Post date: [November 15, 2019, 1:52am UTC](https://discourse.julialang.org/t/type-unstable-function-within-a-struct/31110/1 "2019-11-15T01:52:57Z")
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.
```julia
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:
```julia
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?
---
### Author:  [@jkbest2](https://discourse.julialang.org/u/jkbest2)
#### Post date: [November 15, 2019, 2:20am UTC](https://discourse.julialang.org/t/type-unstable-function-within-a-struct/31110/2 "2019-11-15T02:20:19Z")
Every function has its own type (`Function` is an `abstract type`), so you want to parameterize your `struct` by that type. Something like
```julia
struct Cut{F}
member::String
sound::F
end
```