On Saturday, 23 July 2016 at 11:19:34 UTC, rikki cattermole wrote:
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.
Hi and thanks for your quick replay.
A looked to the gl3n code, although the code is clear and clean,
it is not really what I want to do in my example.
The gl3n is eager evaluation. If I write "v = v1+v2+v3;", then it
will create a temporary variable "tmp1=v1+v2;" then a second temp
"tmp2=tmp1+v3;" and finally "v=tmp2;".
what I'm trying to do to use lazy evaluation in order to create
only one tmp that will that will directly hold the result of
v1[i]+v2[i]+v3[i]. That concept is then generalized in order to
perform more optimization based on entire expression trees, no
just tow operands.
And thanks for the suggestion regarding the channel, I'll try to
use it as soon as I have the time. I feel on advantage of the
forum is that it stays for other people and not just for me.
best regards
