# How do a I get a type "stripped" of parameters?
**URL:** https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465
**Category:** General Usage
**Created:** [December 22, 2021, 1:37am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465 "2021-12-22T01:37:12Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@ablaom](https://discourse.julialang.org/u/ablaom)
#### Post date: [December 22, 2021, 1:37am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/1 "2021-12-22T01:37:12Z")
```julia
struct Foo{T} end
```
What function takes `Foo{Int}` and returns the parent `UnionAll` type, `Foo`?
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [December 22, 2021, 1:46am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/2 "2021-12-22T01:46:18Z")
```julia
julia> a
Rational{Int64}
julia> a.name.wrapper
Rational
```
---
### Author:  [@ablaom](https://discourse.julialang.org/u/ablaom)
#### Post date: [December 22, 2021, 2:12am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/3 "2021-12-22T02:12:47Z")
Thanks, but I was wondering if there is something in the public API to do this. Or is this stable? (`a.name` used to have different behaviour, if I recall correctly)
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [December 22, 2021, 2:35am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/4 "2021-12-22T02:35:48Z")
no and no, the objective you’re after is “hacky” to begin with
---
### Author:  [@ablaom](https://discourse.julialang.org/u/ablaom)
#### Post date: [December 22, 2021, 2:42am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/5 "2021-12-22T02:42:40Z")
Can you elaborate on why my query is ill-defined? Are you suggesting that there may be _no_ least upper bound for a concrete type with parameters, among all `UnionAll` types? Or that there could be more than one?
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [December 22, 2021, 2:57am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/6 "2021-12-22T02:57:36Z")
the “wrapper type without parametric types” information is not captured by Julia’s typing system:
```julia
julia> f(x::T{Int64}) where T = T
ERROR:
```
Attempts to grab it will be fully dynamic. Possible solutions include what I described (which should be semi-stable tbh), or `eval()`ing the names, pick your poison
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [December 22, 2021, 3:31am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/7 "2021-12-22T03:31:18Z")
doesn’t look too bad actually
---
### Author:  [@jishnub](https://discourse.julialang.org/u/jishnub)
#### Post date: [December 22, 2021, 4:12am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/8 "2021-12-22T04:12:11Z")
I think `eval(nameof(Foo{T} where T))` does what you’re looking for, but it’s not type-stable.
```julia
julia> struct Foo{T} end
julia> eval(nameof(Foo{Int}))
Foo
```
This is the solution that was alluded to above, but recommended against.
---
### Author:  [@ablaom](https://discourse.julialang.org/u/ablaom)
#### Post date: [December 22, 2021, 4:48am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/9 "2021-12-22T04:48:01Z")
Great. In my use case performance is not important.
---
### Author:  [@j\_verzani](https://discourse.julialang.org/u/j_verzani)
#### Post date: [December 22, 2021, 11:20am UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/10 "2021-12-22T11:20:48Z")
Also see [https://github.com/JuliaObjects/ConstructionBase.jl/blob/master/src/ConstructionBase.jl#L27](https://github.com/JuliaObjects/ConstructionBase.jl/blob/master/src/ConstructionBase.jl#L27) and it’s note [https://github.com/JuliaObjects/ConstructionBase.jl/blob/master/src/constructorof.md](https://github.com/JuliaObjects/ConstructionBase.jl/blob/master/src/constructorof.md). I think that does what you want.
---
### Author:  [@denius](https://discourse.julialang.org/u/denius)
#### Post date: [December 23, 2021, 6:15pm UTC](https://discourse.julialang.org/t/how-do-a-i-get-a-type-stripped-of-parameters/73465/11 "2021-12-23T18:15:47Z")
There is another option:
```julia
basetype(::Type{T}) where T = Base.typename(T).wrapper
```
from [https://github.com/JuliaLang/julia/issues/39952](https://github.com/JuliaLang/julia/issues/39952)