On 04/24/2012 12:15 AM, Eric Niebler wrote:

implicit_expr() returns an object that holds its argument and is convertible to any expression type. The conversion is implemented by trying to implicitly convert all the child expressions, recursively. It sort of worked, but I never worked out all the corner cases, and documenting it would have been a bitch. Perhaps I should take another look. Patches welcome. :-)

I think this is an important issues to solve as far as Proto grokability does.
One of my coworker on NT2 tried to do just this (the norm2 thingy) and he get puzzled by the random crash.

I think we should at least document the issues (I can write that and submit a patch for the doc) and
maybe resurrect this implicit_expr. Do you have any remnant of code lying around so I don't start from scratch ?