On Tuesday, 9 June 2015 at 15:28:16 UTC, Andrei Alexandrescu
wrote:
Following the use of This in Algebraic
(https://github.com/D-Programming-Language/phobos/pull/3394),
we can apply the same idea to Tuple, thus allowing one to
create self-referential types with ease.
Consider:
// A singly-linked list is payload + pointer to list
alias List(T) = Tuple!(T, This*);
// A binary tree is payload + two children
alias Tree(T) = Tuple!(T, This*, This*);
// or
alias Tree(T) = Tuple!(T, "payload", This*, "left", This*,
"right");
// A binary tree with payload only in leaves
alias Tree2(T) = Algebraic!(T, Tuple!(This*, This*));
Is there interest in this? Other application ideas to motivate
the addition?
Yes, I'm interested. As a practical example, how would you
represent a JSON AST type, which might look something like this
in OCaml (type json at the top)
http://mjambon.com/yojson-doc/Yojson.Safe.html
using Algebraic? And once you've encoded it using Algebraic, how
do you operate on it, for example, how would you write a
'toString' on the AST? These are both straightforward in OCaml
(the straightforward yet inefficient toString pracitically writes
itself from the definition, the efficient version with buffers is
only a little more involved) so a D version would be a good test.
