So I do not totally understand the goal of what you are trying to achieve,
but could you try to do this with a macro?
macro value(d)
@show d
quote
println("d at runtime ", $d)
end
end
@ngenerate N T function example{T,N}(A::Array{T,N}, xs::NTuple{N,Real}...)
@nexprs N dim->begin
@nexprs N d->begin
@value(d)
end
end
end
example(rand(2,2), 1.5, 0.7)
So at least the value of d is know at the time when the macro value is run
and you could then call expression generating code based on that value.
dispatching on types of some additional arguments
>
That sounds like you should/could use staged functions for that.
On Tuesday, 30 December 2014 17:59:37 UTC+1, Tomas Lycken wrote:
>
> I’m doing some metaprogramming for Interpolations.jl, and I’m getting
> stuck at an error that I think is due to scoping issues in my nested
> quotes, and I’ve stared at this for so long now I’m not getting anywhere.
>
> I can do the following
>
> matching(d) = quote
> println("Matching: ", $d)
> end
>
> nonmatching(d) = quote
> println("Not matching: ", $d)
> end
>
> @ngenerate N T function example{T,N}(A::Array{T,N}, xs::NTuple{N,Real}...)
> @nexprs N dim->begin
> @nexprs N d->begin
> if d==dim
> eval(matching(d))
> else
> eval(nonmatching(d))
> end
> end
> end
> end
>
> example(rand(2,2), 1.5, 0.7)
>
> and get the expected output:
>
> Matching: 1
> Not matching: 2
> Not matching: 1
> Matching: 2
>
> Examining with macroexpand, I see that the eval calls are still there,
> but for performance reasons I want to avoid them, so I try to rewrite it to
> use eval(ngenerate(...)) instead of @ngenerate ...:
>
> #matching and nonmatching defined as before
>
> ex = ngenerate(
> :N,
> :T,
> :(example{T,N}(A::Array{T,N}, xs::NTuple{N,Real}...)),
> N->quote
> @nexprs $N dim->begin
> @nexprs $N d->begin
> if d==dim
> $(matching(d))
> else
> $(notmatching(d))
> end
> end
> end
> end
> )
>
> eval(ex)
>
> example(rand(2,2), 1.5, 0.7)
>
> But this doesn’t work: I get ERROR: d not defined on $(matching(d)) (and,
> if I comment that one out, $(nonmatching(d))). I’ve tried $(matching($d))
> (ERROR: error compiling anonymous: syntax: prefix $ in non-quoted
> expression) as well as $(matching(esc(d))) and $(esc(matching(d))) (both
> ERROR:
> d not defined), and I’m at a loss for what to try (these errors are all
> thrown at the stage of *defining* the quoted expression, so macroexpand
> hasn’t helped me here either, as I don’t get any expression to call it on…).
>
> Eventually, this will be used to do different things for different array
> dimensions like here, but with both matching and nonmatching also
> dispatching on types of some additional arguments that I left out for
> simplicity, and choosing expressions by means of multiple dispatch this way
> is really at the core of Interpolations.jl, so I can’t move the contents of
> matching and nonmatching out of their respective functions.
>
> Thanks in advance for any ideas that get me forward,
>
> // Tomas
>
>
