# Setminus unicode operator

**URL:** <https://discourse.julialang.org/t/setminus-unicode-operator/18287>\
**Category:** New to Julia\
**Created:** [December 4, 2018, 5:15pm UTC](https://discourse.julialang.org/t/setminus-unicode-operator/18287 "2018-12-04T17:15:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![harven](https://avatars.discourse-cdn.com/v4/letter/h/3da27b/32.png) [@harven](https://discourse.julialang.org/u/harven)\
**Post date:** [December 4, 2018, 5:15pm UTC](https://discourse.julialang.org/t/setminus-unicode-operator/18287/1 "2018-12-04T17:15:17Z")

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I am trying to use the setminus unicode character as a function name but I get an error (julia 1.01).

```
 julia> ∖(A,B) = setdiff(A,B)
 ERROR: syntax: invalid character "∖"

  julia> (∖)(A,B) = setdiff(A,B)
 ERROR: syntax: invalid character "∖"

```

What am I doing wrong here?

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**Author:** ![rdeits](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rdeits/32/286_2.png) [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Post date:** [December 4, 2018, 5:27pm UTC](https://discourse.julialang.org/t/setminus-unicode-operator/18287/2 "2018-12-04T17:27:51Z")

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As far as I know, the only characters which can be used as identifiers or operators are the ones listed here: [julia/julia-parser.scm at master · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/blob/master/src/julia-parser.scm)

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**Author:** ![simonbyrne](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/simonbyrne/32/19_2.png) [@simonbyrne](https://discourse.julialang.org/u/simonbyrne)\
**Post date:** [December 4, 2018, 8:13pm UTC](https://discourse.julialang.org/t/setminus-unicode-operator/18287/3 "2018-12-04T20:13:15Z")

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It is discussed in this issue: [https://github.com/JuliaLang/julia/issues/26361#issuecomment-371849427](https://github.com/JuliaLang/julia/issues/26361#issuecomment-371849427)