# Emulate local static variable?
**URL:** https://discourse.julialang.org/t/emulate-local-static-variable/956
**Category:** General Usage
**Tags:** question
**Created:** [December 14, 2016, 9:31pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956 "2016-12-14T21:31:27Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@e3c6](https://discourse.julialang.org/u/e3c6)
#### Post date: [December 14, 2016, 9:31pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/1 "2016-12-14T21:31:27Z")
Julia has no `static` keyboard. In `C`, a `static` variable inside a function has a value that persists over function calls.
One way to emulate this in Julia is with a `global` variable. This has two limitations: first, this pollutes the global scope; second, a global variable should be `const` for performance, since its type cannot be annotated. What if I want a non-const static variable?
Is there a way to emulate a local static variable in Julia?
Local in the sense that it should be visible only inside the scope of the function that uses it.
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [December 14, 2016, 9:43pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/2 "2016-12-14T21:43:38Z")
I’m not quite sure what `static` mean but I think it is this: A let block and a closure is the usual style. Here an example [https://github.com/JuliaLang/julia/blob/a304c557928d9eaa0a28af5fe96327d5da70d14b/base/random.jl#L1397](https://github.com/JuliaLang/julia/blob/a304c557928d9eaa0a28af5fe96327d5da70d14b/base/random.jl#L1397)
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### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [December 14, 2016, 9:44pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/3 "2016-12-14T21:44:47Z")
It’s unclear what the semantic of a static local variable in julia should be. On possible implementation with a certain semantic is
```julia
julia> macro static(expr)
if Meta.isexpr(:(::), expr)
T = eval(current_module(), expr.args[2])
name = expr.args[1]
else
T = Any
name = expr
end
:($(esc(name)) = $(Ref{T}()))
end
```
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### Author:  [@e3c6](https://discourse.julialang.org/u/e3c6)
#### Post date: [December 14, 2016, 10:55pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/4 "2016-12-14T22:55:35Z")
Can you use this in an example?
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### Author:  [@e3c6](https://discourse.julialang.org/u/e3c6)
#### Post date: [December 14, 2016, 10:56pm UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/5 "2016-12-14T22:56:13Z")
@mauro3 Yes, this works. Thanks.
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### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [December 15, 2016, 12:35am UTC](https://discourse.julialang.org/t/emulate-local-static-variable/956/6 "2016-12-15T00:35:20Z")
Or just do call overloading. This example has 2 constants which can be used inside the function:
```julia
type LotkaVolterra <: ParameterizedFunction
a::Float64
b::Float64
end
f = LotkaVolterra(0.0,0.0)
(p::LotkaVolterra)(t,u,du) = begin
du[1] = p.a * u[1] - p.b * u[1]*u[2]
du[2] = -3 * u[2] + u[1]*u[2]
end
```
The last line makes `f` a function `f(t,u,du)`, and uses the fields `a` and `b` from the type.
Since `f` is just an instance of a type, you can also change these fields outside of the function if you want. `f.a = 1`. Or you can only use them in the function, take your pick.