On Jul 28, 11 05:25, Asger Dam Hoedt wrote:
2011/7/27 Steven Schveighoffer <[email protected]
<mailto:[email protected]>>
On Wed, 27 Jul 2011 15:48:24 -0400, Asger Dam Hoedt
<[email protected] <mailto:[email protected]>> wrote:
Hey
I've very recently started playing around with D, but I seem to
have hit my
head against a bug in dmd. I want to create a Vector class
templated with
its dimension. This works fine until I try to overload the +
operator for my
vector and use it. I then get the error
Error: incompatible types for ((vec) + (vec)): 'Vector!(3)' and
'Vector!(3)'
I've boiled it down to a small example
struct Vector(int D) {
float es[D];
public:
this(immutable float x, immutable float y, immutable float z) {
es[0] = x; es[1] = y; es[2] = z;
}
Vector!(D) opBinary(string s)(immutable Vector!(D) rhs) if
(s == "+") {
Vector!(D) ret;
for(int i = 0; i < D; ++i)
ret.es <http://ret.es>[i] = es[i] + rhs.es <http://rhs.es>[i];
return ret;
}
}
alias Vector!(3) Vector3;
void main() {
Vector3 vec = Vector3(0,1,2);
vec = vec.opBinary!("+")(vec); // This works fine
vec = vec + vec; // This line fails miserably
}
If I replace the template argument in for the argument rhs with
3, then
everything works, but that's not really a nice solution :)
Is it me trying to use templates in a way they aren't meant to
be used or is
this a bug in dmd? If it is a bug, does anyone have an idea how
to solve
this? I wouldn't mind fixing it in dmd myself, I just need some
guidelines.
It is a bug, someone just brought up almost exactly this problem in
d.learn.
http://www.digitalmars.com/__webnews/newsgroups.php?art___group=digitalmars.D.learn&__article_id=28455
<http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=28455>
The proper workaround (and actually, the cleaner solution) is to use
Vector and not Vector!D. Inside a template, the name of the
template is the same as if you invoked the template with the same
template parameters.
If you actually do need a different value for D, I'm not sure what
works.
-Steve
Oh nice. I'll go with the clean solution then and disregard the bug for
now. Thanks for the quick help.
/asger
Actually you shouldn't need to write a vector struct if "+" is all it
required, as D supports array operation already:
void main() {
float[3] x = [1, 3, 5], y = [5, -6, 2];
x[] = x[] + y[];
assert(x == [6, -3, 7]);
}
It is also more efficient than the for-loop since this could use SIMD
operations in some cases.
