Hello, I’m on the way of learning Ocaml, and one of the things I’m most interested about are Functors. I am reading the section on realWorldOcaml about functors, and the first part is quite clear to me. The problems start to appear when you try restrict bypassing the create function. It starts crea…

Thanks @lindig , your example is simple but complete. However, my big concern is about how declaring an internal type that is just an alias to the provided type allows the compiler restrict using the internal types and forces you go through the create function. I understand how the := destructive s…

[image] Danielo_Rodriguez: I just supposed that, being RealWorld Ocaml the only book of reference and having it publicly available everybody would know about it’s examples. “Real World OCaml” is a great book, but is not the language manual (which exists and is quite readable in most places) a…

Is your problem the following? When implementing functor Make, you want to take advantage of knowing the type defined in the functor argument (Key.t). For example, if you know that Key.t is int, you would like to use that knowledge to create values directly. If indeed this is your problem, there is…

Is the part that confuses you the abstract type? That’s a feature of the module system and it’s not limited to functors. For example, you might have an id type that is useful for tracking the objects that your module deals with, but you don’t want users of your module to use it as a normal int by p…

Yes exactly. It’s that. Thank you for your clarification. I’m still unsure how, without using the abstract type at all, you get the opaque benefit. On your example you are declared everything as just Int s. I saw a related answer on another suggested post Curious about needs for private record fiel…

The compiler just figures that on its own if you declare it properly in the module’s signature, as I did above. I’m not familiar with the theory behind it so I couldn’t tell you how exactly. [image] Danielo_Rodriguez: Seems they are also called private fields. Private record fields do not ex…

[image] perry: the language manual (which exists and is quite readable in most places) Exactly, and we can say this is the only book of reference. :slight_smile: The answers for this thread are given here: The module system Destructive substitution By the way, I’ll try to explain how modul…

Thank you very much @kantian !! Your explanation was awesome It’s amazing how putting the same information on different words could make someone (in tis case me) understand something. On the first part (before functors) it’s a bit awkward to me that you Just define the module, the signature and th…

[image] Danielo_Rodriguez: On the first part (before functors) it’s a bit awkward to me that you Just define the module, the signature and then you build the new abstract module by just saying that the first module has te type previously defined: Surely, that’s awkward, but in pratice you’ll …

Again, @kantian , thank you very much. I cant’ ask for more, the concept is clear and your explanations are superb. Now the only thing left is getting familiar with the concept and try to use it at some places. Thank you very much.

Help me to understand functors

Learning

perry September 13, 2018, 10:30pm 24

I managed to get a minute to do the things above. Someone check if I got them right.

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Help me to understand functors

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