John-Carmack quotes the D programming language

[bearophile]

Guillaume Chatelet:
> A very good article by John-Carmack about purity
>
> http://www.altdevblogaday.com/2012/04/26/functional-programming-in-c/

>Returning everything by value is the natural functional 
>programming style, but relying on compilers to always perform 
>return value optimization can be hazardous to performance, so 
>passing reference parameter for output of complex data 
>structures is often justifiable, but it has the unfortunate 
>effect of preventing you from declaring the returned value as 
>const to enforce single assignment.<

Is this what he is talking about?

class Foo {
     int x;
}
const(Foo) bar() pure {
     auto f = new Foo;
     f.x = 1;
     return f;
}
void main() pure {}

----------------------

Regarding D purity I have asked for another little improvements:
http://d.puremagic.com/issues/show_bug.cgi?id=7994

It's related to this other example:


import std.string: text;
string foo() {
     return text(1);
}
void main() pure {
     enum s = foo(); // currently an error
}

Bye,
bearophile