Comments on: Data Constructors and Readability

By: Elliotte

Elliotte — Sat, 07 Feb 2009 01:54:23 +0000

I should probably set the stylesheet not to make pre text bold though…

By: Elliotte

Elliotte — Sat, 07 Feb 2009 01:53:47 +0000

Aha! It worked. Everyone should be able to use pre here now. I’ll to make the same change on the Cafes.

Thanks for the nudge.

By: Elliotte

Elliotte — Sat, 07 Feb 2009 01:53:00 +0000

Let’s see if this works now:

so much depends on
   a red Haskell
     furiously thinking
        green thoughts

By: elharo

elharo — Sat, 07 Feb 2009 01:51:54 +0000

OK. The problem isn’t registration. It’s that pre is specifically disallowed (more accurately, not specifically allowed). let me see if I can fix that.

By: elharo

elharo — Sat, 07 Feb 2009 01:45:01 +0000

Nope, that didn’t work.

By: elharo

elharo — Sat, 07 Feb 2009 01:44:40 +0000

OK, Let’s see if this works:

This is some
preformatted
text
so much depends on
a red Haskell
furiously thinking
green thoughts

By: Elliotte Rusty Harold

Elliotte Rusty Harold — Sat, 07 Feb 2009 01:39:24 +0000

I fixed your comment. I think you have to register to be allowed to use HTML, but I turned off registration a few months ago because no one did, and a security hole had been found in it. Let me turn it back on and see what happens.

By: Michael Day

Michael Day — Sat, 07 Feb 2009 01:14:25 +0000

…and my nicely formatted

has been mangled, sigh.

By: Michael Day

Michael Day — Sat, 07 Feb 2009 01:13:53 +0000

Try Mercury: like Haskell, but more parentheses :)

:- type doc
    --->    char(char)
    ;       text(string)
    ;       line
    ;       concat(doc, doc)
    ;       union(doc, doc).

By: Elliotte Rusty Harold

Elliotte Rusty Harold — Fri, 06 Feb 2009 15:01:05 +0000

Java doesn't have algebraic data types and pattern matching as such, so there these would probably be subclasses. E.g.

public abstract class Doc {
}

public class Empty extends Doc {
}

public class Text extends Doc {

  public Text(String s) {
  }

}

and so forth. This isn't ideal because this isn't how you'd solve this problem in Java. However if one were to imagine a true Haskell equivalent that used Java-like syntax but Haskell semantics you might see something like this:

datatype Doc implements Show, Eq {
  
  constructor Char (Char c);
  constructor Text (String s);
  constructor Line();
  constructor Empty();
  constructor Concat(Doc d1, Doc d2);
  constructor Union(Doc d1, Doc d2);

}

That could mean exactly the same thing as the actual Haskell; but I for one would find it much easier to read. Yes, it takes a little longer to type, but ease of reading trumps ease of typing. Of course we could play with the exact keywords. Maybe adt or data instead of datatype; maybe new instead of constructor, but you get the idea.