In Julia, how to create a function that saves its own internal state?

[pbayer]

Use a closure:

julia> f(state=0) = ()->state+=1
f (generic function with 2 methods)

julia> foo = f()
#7 (generic function with 1 method)

julia> foo()
1

julia> foo()
2

julia> foo()
3

julia> foo.state
Core.Box(3)

julia> foo.state.contents
3