[DGD] lambda operator re-re-visited?

[Dread Quixadhal]

To be fair, I said that exporting an anonymous function is a design mistake
if you can't (or don't) update the reference when you are recompiled.  In
my example, SetLong() needs to be called again from the on_update()
function (or whatever your mudlib does when a recompile happens).

Let's look at the input chaining usage.

A menu system would obviously make use of this, since you'd want to
generate the list of valid options on the fly, as you walk the menus.

So, your user is picking off a menu when the object that presented the menu
gets recompiled.  Presumably, the driver will attempt to call the old
version of their current menu step when the next line of input shows up.
Because the menu system is generic, it can't easily inform the user object
of the updated code, since it doesn't know where that particular user is,
in their menu walking.

What would happen?  If you did nothing, the old version of the menu would
be called with the user having input a choice based on the old options,
which may now mean something different.  Maybe they picked "rename
character" which is now "delete character".

If you caused the old function to become nil, presumably the driver would
generate an error trying to call nil as a function.  The input handler
would have to catch that and restore the default input handler.  The user
would likely end up confused, as they just fell out of the menu and are
back at a normal prompt.

Either way, the user won't be very happy.  But is that a good reason to not
have anonymous functions at all?  It's a good reason to make sure anyone
using them understands their limitations, to be sure.

The ideal solution would be for the freshly recompiled menu object's
on_update() function to change the user's input_to() hook... but that's
likely not possible, since the object would lack the specific user's input
data to know how to do that.

It is possible to have anonymous functions that would be useful, if the
user were careful and understood the implications of using them in a
persistent system. But if you require a 100% bulletproof solution for every
conceivable use case, then I'll stop commenting here, because I don't think
it's possible.  Like the old strtok() function from the C standard library,
it can be very handy, and it can hurt you badly if you don't know what it
does.

Cheers!