# Assignment to multiple targets - how does it work?
**URL:** https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721
**Category:** General Usage
**Tags:** question, indexing, broadcast, array
**Created:** [June 16, 2018, 6:08pm UTC](https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721 "2018-06-16T18:08:20Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@digital\_carver](https://discourse.julialang.org/u/digital_carver)
#### Post date: [June 16, 2018, 6:08pm UTC](https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721/1 "2018-06-16T18:08:20Z")
Given:
```julia
julia> a = zeros(5); b = zeros(5); R = collect(10:10:100);
```
This naturally fails:
```julia
julia> a[1:end] = R
ERROR: DimensionMismatch("tried to assign 10 elements to 5 destinations")
Stacktrace:
[1] throw_setindex_mismatch(::Array{Float64,1}, ::Tuple{Int64}) at .\indices.jl:92
[2] setindex_shape_check(::Array{Float64,1}, ::Int64) at .\indices.jl:143
[3] setindex!(::Array{Float64,1}, ::Array{Float64,1}, ::UnitRange{Int64}) at .\array.jl:618
```
But then this succeeds:
```julia
julia> c, d = R;
julia> c
10
julia> d
20
```
Why doesn’t this fail with a “tried to assign 10 elements to 2 destinations” error? Why does Julia silently discard the rest of the values in such cases?
Also:
```julia
julia> a[1:end],b = R;
julia> (a,)
([10.0, 10.0, 10.0, 10.0, 10.0],)
julia> (b,)
(20,)
```
This is seen as a broadcast of R’s first value into `a` (and gives an appropriate warning in 0.7), whereas:
```julia
julia> m, n, o, p, q, b = R;
julia> (m, n, o, p, q)
(10, 20, 30, 40, 50)
julia> (b,)
(60,)
```
distributes R’s values over the variables.
What will be the semantics of the previous `a[1:end],b = R;` assignment after the deprecation is removed?
And is there an easy way to get the effect of `a[1], a[2], a[3], a[4], a[5], b = R;` with more compact and more generalizable code?
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [June 17, 2018, 6:00am UTC](https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721/2 "2018-06-17T06:00:47Z")
There are two things going on here.
First, [multiple return values are destructured](https://docs.julialang.org/en/latest/manual/functions/#Multiple-Return-Values-1). Whenever you have a comma-separated list of variable names on the left hand side of a `=`, that is treated as a tuple and the iterable on the right hand side is assigned elementwise. Extra values are not.
The other expression is an invocation of `setindex!`, eg
```julia
julia> Meta.lower(Base, :(a[1:end] = R))
:($(Expr(:thunk, CodeInfo(
1 ─ %1 = Base.lastindex(:a)::Any │
│ %2 = :(:)(1, %1)::Any │
│ Base.setindex!(:a, :R, %2) │
└── return :R │
))))
```
`setindex!` checks for conforming sizes, hence the `DimensionMismatch`.
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [August 5, 2021, 12:11pm UTC](https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721/3 "2021-08-05T12:11:10Z")
> [@Tamas\_Papp](#):
>
> First, [multiple return values are destructured](https://docs.julialang.org/en/latest/manual/functions/#Multiple-Return-Values-1).
We often find broken links in old posts like the one above. This should probably be pointing to the manual [here](https://docs.julialang.org/en/v1/manual/functions/#Multiple-Return-Values).
_ **NB:** _
_Could the admins automatically flag all broken links to the respective post authors?_
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [August 5, 2021, 12:19pm UTC](https://discourse.julialang.org/t/assignment-to-multiple-targets-how-does-it-work/11721/4 "2021-08-05T12:19:15Z")
Personally, I would prefer not to be notified or pinged about broken links in posts I made years ago.
Broken links are an inevitable part of the web. Readers can just use search engines to figure out the current URL.