On 23/07/2016 11:05 PM, Etranger wrote:
[snip]
***************** start of code ******************
import std.stdio;
import std.traits;
import std.conv;
struct VecExpression(alias mixins) {
mixin (mixins);
VecSum!(typeof(this), VecExpression!(RHS)) opBinary(string op, alias
RHS)(ref VecExpression!(RHS) rhs)
{
static if (op == "+") return VecSum!(typeof(this),
VecExpression!(RHS))(&this, &rhs);
}
}
mixin template Vec_impl(int n) {
double[n] elems;
@disable this();
this(double[n] e){
elems=e;
}
double opIndex(int i) {
return elems[i];
}
}
alias Vec(alias n) = VecExpression!("mixin
Vec_impl!("~to!string(n)~");"); //Vec(int n) does not work
mixin template VecSum_impl(E1, E2) {
E1 * e1;
E2 * e2;
@disable this();
this(E1 * ee1, E2 * ee2){
e1=ee1;
e2=ee2;
}
double opIndex(int i) {
return (*e1)[i]+(*e2)[i];
}
}
alias VecSum(E1, E2) = VecExpression!("mixin
VecSum_impl!("~fullyQualifiedName!E1~","~fullyQualifiedName!E2~");");
void main()
{
Vec!(3) v1 = Vec!(3)([5., 2., 3.]), v2 = Vec!(3)([1., 4., 3.]), v3 =
Vec!(3)([3., 2., 1.]);
auto res = v1+v2;
for(int i=0; i < 3; ++i){
writefln("%f + %f = %f", v1[i], v2[i], res[i]);
}
auto res2 = res+v3;
for(int i=0; i < 3; ++i){
writefln("%f + %f = %f", res[i], v3[i], res2[i]);
}
writeln(res);
writeln(res2);
// VecExpression!(Vec_impl!(3)) ve; // Error: template instance
Vec_impl!3 mixin templates are not regular templates
}
***************** end of code ******************
My questions:
1- Is there a cleaner way to do it ? I had to use struct because I want
every thing to happen at compile time and on the stack (without gc). And
I had to use string mixins because template mixin does not work the way
I tried to use it ( see the error last line).
2- Is there a safer way to do it (without using pointers) ?
3- Do you think I'll hit a wall with this approach ?
4- Do you known any D libs that uses expression template for linear
algebra ?
I thank you in advance for your help and wish you a nice weekend (and
apologize for my bad english) :)
My goodness that code is awful.
I have a fair idea what you are attempting to do here.
So I'm going to point you directly to gl3n. Its meant for game dev so
won't provide you a 100% solution. But it should give you ideas of how
to do it.
https://github.com/Dav1dde/gl3n/blob/master/gl3n/linalg.d#L49
If you have any questions and want somebody to talk with you instead of
write, reply cycle. Please hop on to Freenode #d channel.
