Custom Blocks

[dsimcha]

== Quote from Andrei Alexandrescu (SeeWebsiteForEmail at erdani.org)'s article
> Chris Williams wrote:
> > I'm not sure whether the design of D 2.0 has stabilized as yet, but if not,
> > I would like to suggest the ability to create custom block types.
> [snip]
> FWIW we've been talking a long time ago about a simple lowering - if the
> last argument to a function is a delegate, allow moving the delegate's
> body outside of the function:
> fun(a, b, c) { body }
>   |
>   V
> fun((a, b, c) { body });
> As far as Walter and I could tell, there are no syntactical issues
> created by such a lowering. But we've been wrong about that in the past
> (me 10x more often than him).
> Andrei

So this would basically allow the creation of custom flow control constructs at
least to a limited extent?  For example:

void unless(T)(T condition, void delegate() executeThis) {
    if(!condition) executeThis();
}

void until(T)(T condition, void delegate() executeThis) {
    while(!condition) executeThis();
}

void main() {
    until(someoneKnowsWhetherPequalsNP() ) {
        writeln("Who knows?");
    }

    unless(P == NP) {
        writeln("P != NP");
    }
}