Thread overview
Is there a "nice" way to access the names of template parameters outside?
July 27

Consider the following template

auto foo(T, int W, int H)(T p1, T p2) { }

Is there a "nice" way from the outside the get the names of the template values?

E.g:

pragma(msg, TemplateParameterNames!(foo)); // AliasSeq!("T", "W", "H") or ["T", "W", "H"]

I know you can find the names values in a very hacky way. (atleast in dmd 2.097.1)

template HackyHack(alias T) {
   enum RawName = T.stringof;
   enum HackyHack = parseRawName(RawName); // Or templateParse!RawString;
}

I currently have the HackyHack solution "working" but I really don't like it and I would be supprised if it works on other dmd version or other compilers.

I know I can do things like:

template foo(T, int W, int H) {
   enum names = ... // some magic with __traits or just assing it to ["T", "W", "H"]
   auto foo(T p1, T p2) { }
}

Use template mixins or other solutions to get what I want but if possible I prefer to just introspect on the template.

Usecase right now is to do some cuda kernel generation from a D shortfunction.

Something like this:

@kernel
auto saxpy(T, int Iters, int N, int Stride)(T a, T* x, T* y, T* output) => q{
    int tid = blockIdx.x * blockDim.x + threadIdx.x;
    for(int idx = tid, int i = 0; i < Iters && idx < N; ++i, idx += Stride) {
        output[idx] = a * x[idx] + y[idx];
    }
};

Would get transformed to:

template<typename T, int Iters, int N, int Stride>
__global__ void saxpy(T a, T* x, T* y, T* output) {
    //Identical function body / parameters and template arguments from the @kernel
    //D function.
    int tid = blockIdx.x * blockDim.x + threadIdx.x;
    for(int idx = tid, int i = 0; i < Iters && idx < N; ++i, idx += Stride) {
        output[idx] = a * x[idx] + y[idx];
    }
}

Really need the names to make this translation, correctly.

Just to be clear i'm not interested in getting the arguments a template was instantiated with. I can use TemplateArgsOf!T for that.

July 27

On Tuesday, 27 July 2021 at 08:15:12 UTC, Lukas Borin wrote:

>

Consider the following template

auto foo(T, int W, int H)(T p1, T p2) { }

Is there a "nice" way from the outside the get the names of the template values?

As far as I'm aware there is no way to introspect on template parameters at all.

July 27

On Tuesday, 27 July 2021 at 09:31:07 UTC, Paul Backus wrote:

>

On Tuesday, 27 July 2021 at 08:15:12 UTC, Lukas Borin wrote:

>

Consider the following template

auto foo(T, int W, int H)(T p1, T p2) { }

Is there a "nice" way from the outside the get the names of the template values?

As far as I'm aware there is no way to introspect on template parameters at all.

Let's say i instantiate the template does that change anything? Can I get the "placeholder" names in any way then?

July 27

On Tuesday, 27 July 2021 at 10:15:51 UTC, Lukas Borin wrote:

>

On Tuesday, 27 July 2021 at 09:31:07 UTC, Paul Backus wrote:

>

On Tuesday, 27 July 2021 at 08:15:12 UTC, Lukas Borin wrote:

>

Consider the following template

auto foo(T, int W, int H)(T p1, T p2) { }

Is there a "nice" way from the outside the get the names of the template values?

As far as I'm aware there is no way to introspect on template parameters at all.

Let's say i instantiate the template does that change anything? Can I get the "placeholder" names in any way then?

I don't think instantiating it changes anything. The underlying issue is that is(symbol == __parameters) doesn't work on templates.