Quick Overview of Julia language [pdf]

Re:Quick Overview of Julia language [pdf] by Jtsummers on Sunday January 10, 2021 @09:49PM (#25723753)

Somehow I missed this comment. But as michaelcampbell wrote, in Ada you'd select the range that made sense for your application.

So if your application makes sense with 0-based (time series in your example) then you can do it:

  Cash_Flows : array (0..max_time) of Double;

It may even make sense to go negative for some things. For instance:

  Object_at_Altitude : array (-100..1000) of Object;

Or characters:

  Selected_Answers : array (range 'a'..'z') of Boolean;

Or a type that you've created:

  type Color is Red, Green, Blue, Yellow, Orange;
  Histogram_of_Colors : array (Color'Range) of Natural;

But a particularly nice thing is that arrays in Ada, unlike C, don't lose their size, so you can always do:

  for I in Cash_Flows'Range loop
    Some_Function(Cash_Flows(I));
  end loop;

So really the index never even has to be directly touched or known after creation.

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Re:Quick Overview of Julia language [pdf] by mcabbott on Monday January 11, 2021 @05:26AM (#25727027)

The Julia translations of these might look as follows:

    using OffsetArrays
    
    cash_flows = zeros(0:max_time)
    
    altitude = zeros(Bool, -100:100)
    
    for I in eachindex(cash_flows)
        some_function(cash_flows[I])
    end
    # or in this case avoiding indexing:
    for cf in cash_flows
        some_function(cf)
    end
    foreach(some_function, cash_flows)

OffsetArrays is not quite a standard library but it's close. A lot of library code will work like this, calling `eachindex` or `axes` so as to be indifferent to how the arrays are indexed, and to pass this behaviour through to outputs as appropriate.

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Re:Quick Overview of Julia language [pdf] by Jtsummers on Monday January 11, 2021 @10:55AM (#25730583)

Thanks. I'll be taking a look a that for my code. I probably won't use this extensively, but it is a feature I have found useful in Ada (though I'm only a hobbyist, I gave up on convincing work to use it). I'm still a novice with Julia, but I'm doing some math heavy code and started exploring it for its relative ease of use (REPL, fast execution after compilation, ergonomics-focused language design).

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