Pattern for a version of spatial coding. For each dimension, there is an unlimited (and possibly zero) number of elements active with a particular location and amplitude. Superpose and append compute the same function: the lists of elements for a common dimension are concatenated. Inner_product computes the sum of the peaks of the superposition functions, subject to the constraints of winning receivers, which is unrelated to the conventional inner product for vectors. Layers using spatial_pattern use more specialized functions than inner_product.