On Thu, Oct 9, 2014 at 8:50 AM, Ivar Nesje <[email protected]> wrote: > How can I return #undef from a function? > >
You will have to modify the internals of Julia so that *#undef* becomes a > value that can be passed around. Currently it isn't, but we have a new > concept in 0.4-dev with nullable types > <http://docs.julialang.org/en/latest/manual/nullable-types/> that might > suit your need. > Please don't try to actually do this – the fact that #undef is not a first-class value is very much by design. Tony Hoare has given entire talks <http://www.infoq.com/presentations/Null-References-The-Billion-Dollar-Mistake-Tony-Hoare> about why including null references as first class values in Algol was a "billion dollar mistake", which was of course, then copied by C, Java, etc. This should perhaps go in our FAQ.
