On Tuesday, 31 March 2015 at 06:50:16 UTC, Andrei Alexandrescu
wrote:
On 3/30/15 11:34 PM, deadalnix wrote:
On Tuesday, 31 March 2015 at 06:20:22 UTC, Andrei Alexandrescu
wrote:
On 3/30/15 8:49 PM, deadalnix wrote:
On Tuesday, 31 March 2015 at 01:01:24 UTC, Andrei
Alexandrescu wrote:
On 3/30/15 5:49 PM, deadalnix wrote:
Why are you doing the replacement top/down rather than
bottom up ?
What would be the alternative? -- Andrei
Doing the replacement bottom up :
a = a++;
a += { auto olda = a; a = a + 1; return olda; }();
a = cast(typeof(a)) (a + { auto olda = a; a = a + 1; return
olda; }());
You need another lowering here because you evaluate a twice.
Consider:
import std.stdio;
int a;
ref int fun() { writeln("meh"); return a; }
void main() {
fun() = i++;
}
Yeah, I had an int in mind. Make it
{
aPtr = &a;
*aPtr = cast(typeof(a)) (*aPtr + { auto olda = *aPtr;
*aPtr = a +
1; return olda; }());
return *aPtr;
}()
So you propose the following lowering for e1 += e2:
e1 += e2
-\>
{
auto __p = &(e1);
*__p = cast(typeof(e1)) (*__p + e2);
}()
This looks contrived and it's no surprise is inconsistent with
opOpAssign as you yourself noted. I prefer the lowering that
identifies += to a function calls with two parameters:
e1 += e2
-\>
(ref a, b) { a = (cast(typeof(a)) (a + b); }(e1, e2)
Other code transformation do not require a function call to
take place,
so why would this require one (which force eager evaluation
of
parameters) ?
Everything needs to be evaluated (and only once).
That is also inconsistent with LTR evaluation.
I don't see how.
a appear on the left of a++. a should be evaluated before a++.
You
propose that it isn't.
I see, thanks.
Guess we should change the spec no matter what. My money is on
the lowering I mentioned.
Andrei
I might be a bit confused here, but from what you're saying:
b += a++;
and
b += ++a;
Are doing the same thing in DMD?
