Enter your Notes name here <firstname_lastname@lotus.com> wrote:
> I seem to remember that back in the old days, when Dylan had
> Scheme-style syntax, that you could add slots to individual instances.
> Can you do this in the current version of Dylan?
No -- it was probably too hard to implement efficiently.
> Also, does Dylan have something like call/cc from Scheme? Thanks!
Sort of. Dylan has first-class continuations, but they have dynamic
extent rather than unlimited extent like in Scheme. You can create
them with the block statement:
block(dynamic-continuation)
// dynamic-continuation is a bound to a first-class continuation
// function, but it is only legal to invoke it within the scope of
// this block. Attempts to call it outside the block will return an
// error.
end;
An examples of use:
// This will search an unsorted binary tree for a value, and
// abort the computation to return #t if it finds it:
define method find-symbol(tree, id) => (answer :: <boolean>);
local method find-cc(tree, id, k)
select (tree by instance?)
<node>
=> find-cc(tree.left, id, ) | find-cc(tree.right, id, k);
<leaf>
=> if (id = tree.key)
k(#t)
else
#f
end if;
end select;
end method find-cc;
block(return)
find-cc(tree, id, return)
end block;
end method find-symbol;
Hope this helps.
Neel