# Immutable expression issue

**URL:** <https://discourse.julialang.org/t/immutable-expression-issue/26396>\
**Category:** General Usage\
**Tags:** question\
**Created:** [July 16, 2019, 12:03am UTC](https://discourse.julialang.org/t/immutable-expression-issue/26396 "2019-07-16T00:03:46Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Aquaman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/aquaman/32/6586_2.png) [@Aquaman](https://discourse.julialang.org/u/Aquaman)\
**Post date:** [July 16, 2019, 12:03am UTC](https://discourse.julialang.org/t/immutable-expression-issue/26396/1 "2019-07-16T00:03:46Z")

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Dear all,

how can define **immutable** in Julia 1.1.0?

e.g.;

```julia

immutable MySingleton end ERROR: syntax: extra token "MySingleton" after end of expression

```

Best regards

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<div class="post-metadata">

**Author:** ![jkbest2](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jkbest2/32/7350_2.png) [@jkbest2](https://discourse.julialang.org/u/jkbest2)\
**Post date:** [July 16, 2019, 12:08am UTC](https://discourse.julialang.org/t/immutable-expression-issue/26396/2 "2019-07-16T00:08:15Z")

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`struct`s are immutable by default in v1.0+.

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<div class="post-metadata">

**Author:** ![Aquaman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/aquaman/32/6586_2.png) [@Aquaman](https://discourse.julialang.org/u/Aquaman)\
**Post date:** [July 16, 2019, 12:36am UTC](https://discourse.julialang.org/t/immutable-expression-issue/26396/3 "2019-07-16T00:36:50Z")

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in Julia 1.0 …

how can we redefine:

```julia

immutable NeoHook{T}
    μ::T
    λ::T
end

```

thanks in advance

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<div class="post-metadata">

**Author:** ![StefanKarpinski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stefankarpinski/32/24_2.png) [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)\
**Post date:** [July 16, 2019, 12:47am UTC](https://discourse.julialang.org/t/immutable-expression-issue/26396/4 "2019-07-16T00:47:58Z")

</div>

`struct`