dispatch on type of ...

tuple_dispatch.jl

module Foos
type Foo{T <: Tuple} 
end 
m1{T}(f::Foo{Tuple{T}}, index::T...) = 42 # suggested by Bill Hart
m2{T}(f::Foo{T}, index::T...) = 42 # what I thought would work
_m3{T}(f::Foo{T}, index::T) = 42 # indirect solution
m3{T}(f::Foo{T}, index...) = _m3(f, index)
end

f1 = Foos.Foo{Tuple{Int}}()
Foos.m1(f1, 9)                  # works
Foos.m2(f1, 9)                  # won't work
Foos.m3(f1, 9)                  # works

f2 = Foos.Foo{Tuple{Int,Symbol}}()
Foos.m1(f2, 9, :a)               # won't work
Foos.m2(f2, 9, :a)               # won't work
Foos.m3(f2, 9, :a)               # indirect, works