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What does double dot (..) in Julia Programming Language mean?

For example in the code below, x is defining the domain, but why is there the double dot between 0 and 4pi?

using ApproxFun
x=Fun(identity,0..4π)
Solution

  • .. is not part of Julia, rather part of the packages used by ApproxFun.

    It is used to represent intervals, see the code below

    julia> u = 1..3
1..3

julia> dump(u)
Interval{:closed,:closed,Int64}
  left: Int64 1
  right: Int64 3

    So this is just a convenience constructor for the Interval object, see:

    julia> 1..3 === Interval{:closed,:closed,Int64}(1,3)
true