On 10/17/2012 02:09 AM, H. S. Teoh wrote:
On Wed, Oct 17, 2012 at 01:09:09AM +0200, Timon Gehr wrote:
[...]
The following code is free of allocations if the compiler
implementation is correct:
auto cprod(R1,R2)(R1 A, R2 B) {
return zip(sequence!"n"(cast(size_t)0), A.save, B.save,
repeat(A), repeat(B))
.map!(function(a) => chain(
zip(repeat(a[1]), take(a[4].save,a[0])),
zip(take(a[3].save,a[0]+1), repeat(a[2]))
)).joiner;
}
It also works around the issue. (note that I got rid of some UFCS
calls. The reason is that we don't know whether R1 and/or R2 actually
have a member named 'take' or 'repeat' that would hijack the function
we want to call.)
[...]
Hmph. I seem to be running into one compiler bug after another. Using
the above code, which solves the initial problem, I get into another
problem:
void main() {
auto A = sequence!"2*n"(0);
auto B = sequence!"2*n+1"(0);
auto AB = cprod(A,B);
auto C = sequence!"100+n"(0);
auto D = sequence!"200+n"(0);
auto CD = cprod(C,D);
}
DMD gives this bizarre error:
Error: function
test3.cprod!(Sequence!("2*n",Tuple!(int)),Sequence!("2*n+1",Tuple!(int))).cprod.map!(__funcliteral2).map!(Zip!(Sequence!("n",Tuple!(uint)),Sequence!("100+n",Tuple!(int)),Sequence!("200+n",Tuple!(int)),Repeat!(Sequence!("100+n",Tuple!(int))),Repeat!(Sequence!("200+n",Tuple!(int))))).map
is a nested function and cannot be accessed from test3.cprod!(Sequence!("100+n",Tuple!(int)),Sequence!("200+n",Tuple!(int))).cprod
Commenting out either the first three lines (A, B, AB) or the second
three lines (C, D, CD) makes the problem go away.
Looking more carefully at the error message, it appears that dmd is for
some strange reason trying to reuse the first instance of cprod when
compiling cprod(C,D). This is totally wrong, since they should be
completely separate instantiations. Why this is so, I've no idea. :-(
T
Looks like http://d.puremagic.com/issues/show_bug.cgi?id=8542
But your test case is somewhat simpler, so it might be useful to add it
there.
