On Sun, 19 Aug 2012 14:08:17 +0200, bearophile <bearophileh...@lycos.com>
wrote:
Walter Bright:
Oh come on. That's called a "user defined type."
This D code compiles and it throws an "Enforcement failed" Exception at
runtime:
import std.typecons: Nullable;
void main() {
Nullable!int x;
int y = x;
}
With a different type system the compiler makes sure at compile-time
that x is not empty (this means the compiler makes sure in no code paths
x is used before testing it contains something), avoiding the run-time
exception.
We could define a Nullable!T that does not allow access to the payload
value, and only give that access inside a special function, like
pattern matching in other languages:
Nullable!int a;
int n = a.match!(
(int x) => x,
(None n) => 0
);
--
Simen
