Code Golf
petStorm
Given two lists only containing positive integers, return all items among these two lists that aren't contained in both of the lists.

## Rules
From the set definition:
> A set is a collection of definite distinct items.

* So you can assume the items in the input lists are always unique.
* You can also take input as a set if your language supports it.

## Test cases
[Here](https://tio.run/##bY2xCsMgFAD39xVv9JFnIG2nUAr6FYI4pEWKEE1RIRTy7zZZSofecNPB@TxP6Sl9eeTwqq1BeUehWBPKG@CONbhtaPAqUTGmpeIcSi1j9PHuszCMmhxg1/2W@n@pyPUAcQpJWPc9hGVcc6heHGs78InPju1uvjiivrUP) is a sample program that generates the test cases.
```
[1,2,3],[2,3,4] -> [1,4]
```
Top Answer Kotlin
ajc2
# [Kotlin], 16 bytes

    {a,b->a-b+(b-a)}

[Try it online!][TIO-k8z2em2a]

[Kotlin]: https://kotlinlang.org
[TIO-k8z2em2a]: https://tio.run/##y84vycnM@1@WmKNQXJmbkplmpaARnFpi45lXYqejAGNpKujawTkKtv@rE3WSdO0SdZO0NZJ0EzVr/6eV5inkJmbmaWgqVHNxgkxLVLBVKE4t8U/TMNQx0jHWhIgmwUWBYjomQNGCosy8Eg2I3RpAYzU1uWr/AwA "Kotlin – Try It Online"
Answer #2 Julia 1.0
Lennart Jonsson
# [Julia 1.0], 24 bytes

```julia
symdiff([1,2,3],[2,3,4])
```

[tio.run](https://tio.run/##yyrNyUw0rPj/v7gyNyUzLU0j2lDHSMc4VicaSOqYxGr@/w8A)
Answer #3 APL (Dyalog Unicode)
Adám
# [APL (Dyalog Unicode)], 3 bytes

```apl
∪~∩
```
[Try it online!][TIO-k9kfg28t]

`∪` union `~` without `∩` intersection.

[APL (Dyalog Unicode)]: https://www.dyalog.com/
[TIO-k9kfg28t]: https://tio.run/##SyzI0U2pTMzJT////1HHqrpHHSv/pz1qm/Cot@9RV/Oj3jWPerccWm/8qG3io76pwUHOQDLEwzP4v6GCkYKxQhqYNAEA "APL (Dyalog Unicode) – Try It Online"
Answer #4 CJam
EsolangingFruit
# [CJam], 3 bytes

    {^}

[Try it online!][TIO-k9hb52gb]

[CJam]: https://sourceforge.net/p/cjam
[TIO-k9hb52gb]: https://tio.run/##S85KzP1fWPe/Oq72f13B/2hDBSMF41iFaCCpYBILAA "CJam – Try It Online"
Answer #5 J
Nobody
# [J](https://jsoftware.com), 8 bytes

```J
,-.[-.-.
```
[Try it online!](https://tio.run/##y/qvpKdenKJga6WgrqCjYKBgBcS6egrOQT5u/3V09aJ19XT1/mtypSZn5CsYKhgpGCsAVYMoE4SYKUzMHCZmCuRYgESNTRTMQYr/AwA)

Concatenate minus intersection.

Simply concatenates (`,`) the two arguments and set-subtracts (`-.`) from it the intersection ($f(A,B)=A{\backslash}(A{\backslash}B)$ ; `[ -. -.`) of them.

edit: right after posting this, I realized there is a very clever 6-byte solution (I saw it after I checked the answers to this challenge on CGSE). I didn't come up with it myself so I won't count it towards my score, but I'm putting it here anyway.

`-.,-.~`

Explanation:

Concatenate (`,`) A\B (`-.`) and B\A (`-. ~`)

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