Consider the following expression:
julia> macroexpand(:(@nexprs 3 j->(out[r, ix] *= z[r, i_{3-j+1}]) ))
quote
out[r,ix] *= z[r,i_3]
out[r,ix] *= z[r,i_2]
out[r,ix] *= z[r,i_1]
end
What I would really like to be able to do is have a macro generate the
expression
julia> ... some magic incantation here
quote
out[r,ix] = z[r,i_3]*z[r,i_2]*z[r,i_3]
end
Does anyone see an easy way to do this?
For some context, this appears in the following block of code:
immutable Degree{N} end
function n_complete(n::Int, D::Int)
out = 1
for d=1:D
tmp = 1
for j=0:d-1
tmp *= (n+j)
end
out += div(tmp, factorial(d))
end
out
end
@generated function complete_polynomial!{N}(z::Matrix, d::Degree{N},
out::Matrix)
complete_polynomial_impl!(z, d, out)
end
function complete_polynomial_impl!{T,N}(z::Type{Matrix{T}},
::Type{Degree{N}},
::Type{Matrix{T}})
quote
nobs, nvar = size(z, 1), size(z, 2)
if size(out) != (nobs, n_complete(nvar, $N))
error("z, out not compatible")
end
out[:, 1] = 1.0
out[:, 2:nvar+1] = z
# reset first column to ones
@inbounds for i=1nobs
out[i, 1] = 1.0
end
# set next nvar columns to input matrix
@inbounds for n=2:nvar+1, i=1:nobs
out[i, n] = z[i, n-1]
end
# reset all trailing columns to 1s
@inbounds for n=nvar+2:size(out, 2), i=1:nobs
out[i, n] = 1.0
end
ix = nvar+1
@nloops($N, # number of loops
i, # counter
d->((d == $N ? 1 : i_{d+1}) : nvar), # ranges
d->(d == $N ? nothing :
(ix += 1 ; for r=1:nobs @nexprs $N-d+1 j->(out[r, ix]
*= z[r, i_{$N-j+1}]) end)),
Expr(:block, :nothing) # bodyexpr
)
out
end
end
I would like to be able to generate the expression I mentioned before for
two reasons: 1.) so I can avoid having to set all trailing columns to 1s
before the @nloops and 2.) so I can only traverse out once in the prexpr
part of the @nloops call.
Any suggestions would be most welcome. Thanks!
