### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [December 19, 2021, 5:00pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/7 "2021-12-19T17:00:08Z")
Actually I don’t understand the `by` keyword, as the list is expected to be already sorted…
So, using `by=first` here, seems to also apply `first` to `:b` which raises the original error. Therefor my idea not using `by` but defining `lt`.
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [December 19, 2021, 5:01pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/8 "2021-12-19T17:01:07Z")
This may clarify a bit more:
```julia
julia> Base.first(s::Symbol)=s
julia> searchsortedfirst(a, :b; by=first)
2
```
---
### Author:  [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)
#### Post date: [December 19, 2021, 5:06pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/9 "2021-12-19T17:06:22Z")
The `:by` keyword tells which part of the objects should be compared.
I thought that the object to compare would be compared to the `by` part since the following works:
```julia
julia> a=[1=>"a",3=>"b"]
2-element Vector{Pair{Int64, String}}:
1 => "a"
3 => "b"
julia> searchsortedfirst(a,3;by=first)
2
```
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [December 19, 2021, 5:15pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/10 "2021-12-19T17:15:24Z")
> [@Jean\_Michel](#):
>
> The `:by` keyword tells which part of the objects should be compared. So `by=first` is the
> same as `lt=(x,y)->first(x) first(:b)
ERROR: MethodError: no method matching iterate(::Symbol)
```
So defining `first` on type `Symbol`, as in my last post, resolves this, but it’s not the recommended solution. The recommended solution is defining the less-than relation between `Pair{Symbol, Int64}` and `Symbol`.
Now you are editing your replies… this is becoming to awkward, so I think, it’s all said, perhaps not in the best understandable way.
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [December 19, 2021, 5:17pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/11 "2021-12-19T17:17:14Z")
Integer number are per definition iterables:
```julia
julia> first(1)
1
```
There is quite some discussion about this, which I don’t look up for you now, but it is like that.
Symbols are not iterable.
---
### Author:  [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)
#### Post date: [December 19, 2021, 5:18pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/12 "2021-12-19T17:18:46Z")
I edit my posts when I have written a mistake and hope the edit is before you read.
I think I understand: the `by` is also applied to the value I want to compare (unfortunately)
and my last example works by a fluke (that first is valid for an Int).
---
### Author:  [@oheil](https://discourse.julialang.org/u/oheil)
#### Post date: [December 19, 2021, 5:19pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/13 "2021-12-19T17:19:11Z")
And I did it anyways:
[https://github.com/JuliaLang/julia/issues/7903](https://github.com/JuliaLang/julia/issues/7903)
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [December 19, 2021, 6:20pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/14 "2021-12-19T18:20:29Z")
The discussion got complicated and is solved, but it was not clear to me if it is clear to the reader that this works:
```julia
julia> a=[:a=>1,:b=>2,:b=>3,:c=>4]
4-element Vector{Pair{Symbol, Int64}}:
:a => 1
:b => 2
:b => 3
:c => 4
julia> searchsortedfirst(a, (:b,); by=first)
2
julia> searchsortedfirst(a, (:c,); by=first)
4
```
(any catch here I don’t see?)
I see now: the order is on the values, not on the keys… (though I’m unsure now, if `by=first`, if that is not what one wants really)
---
### Author:  [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)
#### Post date: [December 19, 2021, 6:25pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/15 "2021-12-19T18:25:19Z")
It works since `first((:b,))` is defined and returns `:b`. I think I projected in my mind a better interface for the `searchsorted...` routines in case of `by` keyword that the actual interface,that is I hoped that the `by` function would not be applied to the value given to compare, which seemed natural.
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [December 19, 2021, 6:28pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/16 "2021-12-19T18:28:30Z")
Yes, that is catchy. I have been there is some more mundane examples, like:
```julia
julia> searchsortedfirst([1,2,3,4], 2, by=x -> x^2)
2
julia>
```
Sometimes this is very annoying, because it requires one to define the inverse function to be able to search, something that is not always trivial.
---
### Author:  [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)
#### Post date: [December 19, 2021, 6:30pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/17 "2021-12-19T18:30:05Z")
Perhaps change the meaning of `by` in `julia2.0`?
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [December 19, 2021, 6:31pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/18 "2021-12-19T18:31:18Z")
I think that I was convinced that that is the reasonable behavior, but I don’t remember why. Let me see if I find the thread. (I found the thread, but it was not really related, I just learnt that there, not really with a good justification).
---
### Author:  [@Jean\_Michel](https://discourse.julialang.org/u/Jean_Michel)
#### Post date: [December 19, 2021, 10:44pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/19 "2021-12-19T22:44:06Z")
Perhaps we could ask for a compromise, that is a keyword to the `searchsorted...` function which would signify that the `by` function is _not_ applied to the object to compare.
---
### Author:  [@lmiq](https://discourse.julialang.org/u/lmiq)
#### Post date: [December 19, 2021, 11:04pm UTC](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332/20 "2021-12-19T23:04:45Z")
```julia
apply =
```
maybe
[Next page](https://discourse.julialang.org/t/problem-with-searchsortedfirst/73332.md?page=2)