# \_set\_value!(w, key, val) = w\[key\] = val

**URL:** https://discourse.julialang.org/t/set-value-w-key-val-w-key-val/108656
**Category:** General Usage
**Tags:** question
**Created:** [January 11, 2024, 2:53am UTC](https://discourse.julialang.org/t/set-value-w-key-val-w-key-val/108656 "2024-01-11T02:53:17Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![jiang\_ming\_zhang](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jiang_ming_zhang/32/204063_2.png) [@jiang\_ming\_zhang](https://discourse.julialang.org/u/jiang_ming_zhang)
#### Post date: [January 11, 2024, 2:53am UTC](https://discourse.julialang.org/t/set-value-w-key-val-w-key-val/108656/1 "2024-01-11T02:53:17Z")

</div>

Is this equivalent to the function

```julia
function _set_value!(w, key, val)
       w[key] = val
end 

```

---

<div class="post-metadata">

### Author: ![jar1](https://avatars.discourse-cdn.com/v4/letter/j/c0e974/32.png) [@jar1](https://discourse.julialang.org/u/jar1)
#### Post date: [January 11, 2024, 3:07am UTC](https://discourse.julialang.org/t/set-value-w-key-val-w-key-val/108656/2 "2024-01-11T03:07:43Z")

</div>

Yes

---

<div class="post-metadata">

### Author: ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)
#### Post date: [January 11, 2024, 4:52am UTC](https://discourse.julialang.org/t/set-value-w-key-val-w-key-val/108656/3 "2024-01-11T04:52:02Z")

</div>

Note the expression `A[3] = 2` gets turned into a function call to `Base.setindex!`:

```julia
julia> A = zeros(5)
5-element Vector{Float64}:
 0.0
 0.0
 0.0
 0.0
 0.0

julia> function f(A)
           A[3] = 2
       end
f (generic function with 1 method)

julia> @code_lowered f(A)
CodeInfo(
1 ─ Base.setindex!(A, 2, 3)
└── return 2
)

```