On Monday, 18 June 2012 at 14:48:37 UTC, deadalnix wrote:
Le 18/06/2012 16:44, Mehrdad a écrit :
Interesting, making the delegate `pure' doesn't change
anything either.
So 'pure' doesn't let you "infer something just by looking at
the code
either", right?
It does ! It tell you that the function have no side effect,
and that the function called with identical arguments will
return identical results.
pure will not ensure constness or immutability. const and
immutable are made for that.
The fact that D decouple purity and immutability is a very nice
design decision and is explained nicely here :
http://klickverbot.at/blog/2012/05/purity-in-d/
Identical calls giving identical results? What?
import std.stdio;
struct S
{
this(int a)
{
this.a = a;
this.increment = { return this.a++; };
}
int a;
int delegate() pure increment;
auto oops() const { return this.increment(); }
}
void main()
{
auto c = immutable(S)(0);
writeln(c.oops()); // 0
writeln(c.oops()); // 1
writeln(c.oops()); // 2
writeln(c.oops()); // 3
writeln(c.oops()); // 4
writeln(c.oops()); // 5
}
