# Error when adding vectors
**URL:** https://discourse.julialang.org/t/error-when-adding-vectors/80541
**Category:** New to Julia
**Tags:** question, struct
**Created:** [May 5, 2022, 1:22pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541 "2022-05-05T13:22:05Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@vamp](https://discourse.julialang.org/u/vamp)
#### Post date: [May 5, 2022, 1:22pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/1 "2022-05-05T13:22:05Z")
Hello, I am new here and I would like to know why I can’t add these vectors:
```nohighlight
mutable struct Mystruct
a::Int
b::SVector{3, Int64}
c::Int
end
v1=[Mystruct(1,(-2,-2,2),1)]
v2=[Mystruct(2,(2,2,2),1)]
v3 = v1 + v2
```
`ERROR: MethodError: no method matching +(::Mystruct, ::Mystruct)`
---
### Author:  [@skleinbo](https://discourse.julialang.org/u/skleinbo)
#### Post date: [May 5, 2022, 1:28pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/2 "2022-05-05T13:28:43Z")
By “add” you mean, join `v1` and `v2`?
Either `[v1; v2]` or `vcat(v1, v2)` does that. This will return a fresh vector. If you want to add the elements of `v2` to the existing `v1`, use `append!(v1, v2)`.
```julia
julia> [v1; v2]
2-element Vector{Mystruct}:
Mystruct(1, [-2, -2, 2], 1)
Mystruct(2, [2, 2, 2], 1)
```
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [May 5, 2022, 1:30pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/3 "2022-05-05T13:30:25Z")
If you actually want to add instances of your type, you will have to tell Julia how addition is supposed to work for them. Something like:
```julia
julia> v1=[Mystruct(1,[1,2],1)]
1-element Vector{Mystruct}:
Mystruct(1, [1, 2], 1)
julia> v2=[Mystruct(1,[3,4],1)]
1-element Vector{Mystruct}:
Mystruct(1, [3, 4], 1)
julia> +(x::Mystruct, y::Mystruct) = Mystruct(x.a + y.a, x.b .+ y.b, x.c + y.c)
+ (generic function with 209 methods)
julia> v1+v2
1-element Vector{Mystruct}:
Mystruct(2, [4, 6], 2)
```
(note here I’ve simplified things by replacing the `SVector` with a plain `Vector` in the struct definition)
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [May 5, 2022, 1:40pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/4 "2022-05-05T13:40:25Z")
Don’t we need first to `import Base.+` , before adding the new methods?
---
### Author:  [@vamp](https://discourse.julialang.org/u/vamp)
#### Post date: [May 5, 2022, 1:42pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/5 "2022-05-05T13:42:05Z")
> [@nilshg](#):
>
> `v2=[Mystruct(1,[3,4],1)]`
With
```julia
mutable struct Mystruct
a::Int
b::Vector{ Int64}
c::Int
end
v1=[Mystruct(1,[1,2],1)]
v2=[Mystruct(1,[3,4],1)]
+(x::Mystruct, y::Mystruct) = Mystruct(x.a + y.a, x.b .+ y.b, x.c + y.c)
import Base: +
v1 + v2
```
`ERROR: MethodError: no method matching +(::Vector{Mystruct}, ::Vector{Mystruct}) You may have intended to import Base.:+`
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [May 5, 2022, 1:46pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/6 "2022-05-05T13:46:02Z")
The `import` needs to come before the definition of the function for this to work.
(Test it in fresh REPL.)
---
### Author:  [@vamp](https://discourse.julialang.org/u/vamp)
#### Post date: [May 5, 2022, 1:49pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/7 "2022-05-05T13:49:00Z")
```julia
using StaticArrays
mutable struct Mystruct
a::Int
b::SVector{3, Int64}
c::Int
end
v1=[Mystruct(1,(-2,-2,2),1)]
v2=[Mystruct(2,(2,2,2),1)]
import Base: +
+(x::Mystruct, y::Mystruct) = Mystruct(x.a + y.a, x.b .+ y.b, x.c + y.c)
v3 = v1 + v2
```
Done, thanks!
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [May 5, 2022, 2:11pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/8 "2022-05-05T14:11:15Z")
Sorry I had actually done this but forgot to copy that line!
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [May 5, 2022, 2:21pm UTC](https://discourse.julialang.org/t/error-when-adding-vectors/80541/9 "2022-05-05T14:21:25Z")
> [@vamp](#):
>
> `v1=[Mystruct(1,(-2,-2,2),1)]`
Why the braces here? This is creating a one-element vector of your structures. Is that what you want?