Re: [Haskell-cafe] Re: [Haskell] Top Level <-

I actually was more interested in the problems with the "obvious fix" for this, namely the "construct on first use" idiom: int A(int a) { static int aa = a; return aa; } int B() { return A(3); } int C() { return A(7); } int D() { if (today() == "Tuesday") B(); else C(); return a(0); } What is the value of D? Notice that this is never a problem with pure functions. The problem is that today() makes this an IO monad, and the swearing starts again. Dan Bryan O'Sullivan wrote:

On Fri, Aug 29, 2008 at 4:33 PM, Dan Weston wrote:

...

C++ faced this very issue by saying that with global data, uniqueness of initialization is guaranteed but order of evaluation is not.

In C++ circles, this is referred to as the "static initialization order fiasco", and it is a frequent cause of crashes that are very difficult to debug.

http://www.parashift.com/c++-faq-lite/ctors.html#faq-10.12

I think it would be fair to say that C++ pushed this problem off to every user of the language. I haven't seen a coherent description of what the semantics of top-level "<-" should be, but avoidance of widespread swearing would be at the top of my list of requirements.