The built-in type `CartesianIndex` supports adding and subtracting, and presumably also multiplication. It is implemented very efficiently, based on tuples.
Otherwise, to generate efficient code, you might have to make use of "generated functions". These are similar to macros, but they know about the types upon which they act, and thus know the value of `N`. This is a bit low-level, so I'd use this only if (a) there is not other package available, and (b) you have examined Julia's performance and found it lacking. I would avoid overloading operators for `NTuple`, and instead us a new immutable type, since overloading operations for Julia's tuples can have unintended side effects. -erik On Wed, Aug 10, 2016 at 9:57 AM, 'Bill Hart' via julia-users < [email protected]> wrote: > Does anyone know an efficient way to add NTuples in Julia? > > I can do it using recursive functions, but for various reasons this is not > efficient in my context. I really miss something like tuple(a[i] + b[i] for > i in 1:N) to create the resulting tuple all in one go (here a and b would > be tuples). > > The compiler doesn't do badly with recursive functions for handling tuples > in very straightforward situations, but for example, if I want to create an > immutable type based on a tuple the compiler doesn't seem to be able to > handle the necessary optimisations. At least, that is what I infer from the > timings. Consider > > immutable bill{N} > d::NTuple{N, Int} > end > > and I want to add two bill's together. If I have to add the tuples > themselves using recursive functions, then I no longer seem to be able to > do something like: > > A[i] = B[i] + C[i] efficiently, where A, B and C are arrays whose elements > are of type bill. > > I know how to handle tuples via arrays, but for efficiency reasons I > certainly don't want to do that, e.g. tuple([a[i] + b[i] for i in 1:N]...). > > Bill. > -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/
