On Tuesday, 14 March 2023 at 10:19:24 UTC, Elfstone wrote:
```D
struct Matrix(S, size_t M, size_t N)
{
}
alias Vector(S, size_t N) = Matrix!(S, N, 1);
enum isVector(V) = is(V == Vector!(S, N), S, size_t N); // it
doesn't work
enum isVectorCorrect(V) = is(V == Matrix!(U, N, 1), U, size_t
N); // the "correct" way and how much I like to REPEAT myself!
void foo(U)(Vector!(U, 3) a)
{
}
void bar(U)(U a) if (isVector!U)
{
}
void main()
{
import std.stdio;
Vector!(float, 3) v;
foo(v); // Error: none of the overloads of template
`app.doSomething` are callable using argument types
`!()(Matrix!(float, 3LU, 1LU))
bar(v); // failed constraint isVector!U
}
```
I went back to some of my old code and couldn't stand what I
had ended up with - If I already have a well-defined `Vector`,
why do I have to write extra code to implement `isVector`, and
use `isVector` instead of simply declaring the param to be
`Vector`?
But that's simply the current state: it looks like DIP1023
isn't going anywhere, and I'm not a compiler expert.
Note that I had to repeat `Matrix!(S, N, 1)` to for both
`Vector` and `isVector`.
Is there a way around this?!
--
It can get worse.
```D
alias Vec2(S) = Vector!(S, 2);
alias Vec3(S) = Vector!(S, 3);
enum isVec3(V) = is(V == Matrix!(S, 2, 1), S);
enum isVec3(V) = is(V == Matrix!(S, 3, 1), S);
void foobar(U)(U v) if (isVec3!U);
```
It works, but it hurts my eyes.
**just a noob seeing if can solve this no idea if this is vaild
code**
```D
// T int, double, float
// N element
// V number of elements / weight
template Matrix(T, size_t N = 2, size_t V = 1)
{
struct Matrix
{
static if (is(Matrix!(T, N, V)))
{
alias enum isVec3 = N == 3;
alias enum isVec2 = N == 2;
alias enum isVaildVec = (isVec2 || isVec3);
}
}
}
bool foo(T)(Matrix!T element)
{
return element.isVaildVec;
}
void main()
{
import std.stdio : writeln;
// defaults to vec2 of 1
Matrix!int c;
c.foo.writeln;
c.writeln;
}
```
