Implementing a programming language in D: Lexical Analysis

Re:Implementing a programming language in D: Lexical Analysis by tomjakubowski on Monday December 28, 2015 @09:19PM (#10804775)

Can you name the variants to distinguish two variants which "carry" the same types? It wouldn't be as useful if you can't express something like:

    enum ConnState {
        Disconnected,
        Connecting,
        Connected(net::TcpSocket),
        Transferring(net::TcpSocket),
     }

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Re:Implementing a programming language in D: Lexical Analysis by jeremiep on Tuesday December 29, 2015 @12:46AM (#10805434)

I would probably do it like this in D (disclaimer: I haven't tested this code!)

  import std.typecons;
  import std.socket;
  import std.variant;

  struct Disconnected {}
  struct Connecting {}

  alias Connected = Typedef!(TcpSocket, null, "connected");
  alias Transferring = Typedef!(TcpSocket, null, "transferring");

  alias ConnState = Algebraic!(Disconnected, Connecting, Connected, Transferring);

You could use plain structs instead of the typedef template for the same result.

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Re:Implementing a programming language in D: Lexical Analysis by p0nce on Tuesday December 29, 2015 @06:45AM (#10806251)

I see what you mean.

You can create such new types with std.typecons.Typedef https://dlang.org/phobos/std_typecons.html#.Typedef

Though it's less pretty.

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