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
