Example of Rust code

[Walter Bright]

On 8/10/2012 3:42 PM, bearophile wrote:
> Walter Bright:
>
>> I'd say we're doing all right.
>
> Are you serious?

You can also do things called "expression templates" in D:


import std.stdio;

auto val(T)(T v) { static struct S { T v; int eval() { return v; }} auto s = 
S(v); return s; }

auto plus(A,B)(A a, B b) { static struct S { A a; B b; int eval() { return 
a.eval() + b.eval(); }} auto s = S(a,b); return s; }

auto minus(A,B)(A a, B b) { static struct S { A a; B b; int eval() { return 
a.eval() - b.eval(); }} auto s = S(a,b); return s; }

void main() {

     auto x = minus(val(5), plus(val(3), val(1)));

     writeln("val: ", x.eval());
}

relying on "parametric polymorphism". You could reduce the repetitive 
boilerplate by using a template mixin, but I just banged this out in a few 
minutes, and it illustrates the idea. Note that there is no heap allocation 
anywhere, nor even any testing/branching.

The compiler should inline this, but doesn't, but that's not a fault in D. The 
inliner could be improved.