Re: C++0x - a quick and dirty introduction (as of November 2007)
Assuming, recursion would be supported, this would be written as
follows:
constexpr int factorial(int n)
{
if (n == 1)
return 1;
else
return n * factorial(n-1);
}
This would seem even more readable as the syntax of D ;-)
I agree with that.
constexpr seems like it would solve many of the problems more
elegantly but there are certainly cases where it wouldn't do the job.
I have never programmed in D but the as far as I understand it "static
if" allows the you to include or exclude bits of code at will as if
you were using #if and #endif but using compile-time information. Note
that the the keyword "is" allows you to bring type information to the
table too. This is one of those things one finds oneself trying to do
but having to use include_if, inelegant inheritance structures and
other things you would rather not show your parents.
I don't want to get "feature happy" but the "static if" seems to me as
one with no knowledge in the area at all rather an easy feature to add
to a compiler, relatively speaking. That is to say it doesn't mess
with anything else, it just adds a layer of logic on top. The compiler
works out which part of the code it needs to compile then tries to do
so. There are other related features in D which might seems sensible
in place but would work less naturally in c++.
The net result is to remove the need for 90% if not all precompiler
stuff, which can't really do the job anyway because it doesn't have
the (compile time) information and the template tricks that are there
to bypass the fact that at compile time you don't officially have the
power to pick which bits of the code you want to compile.
It seems like a win-win feature in a world full of tradeoffs but it is
probably not that simple. Please let me know why I'm wrong (or, less
likely, right).
on conditional compilation:
http://www.digitalmars.com/d/version.html
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