Terms and Definitions

For the purposes of this specification, the following terms and definitions apply.

Normative Keywords

This specification aims to follow RFC 2119 and use the following keywords to indicate requirement levels:

must: a definition or behavior is an absolute requirement of this specification.

must not: a definition or behavior is an absolute prohibition of this specification.

should: valid reasons may exist to ignore a definition or behavior in particular circumstances; however, the full implications must be understood and carefully weighed before choosing a different course.

should not: valid reasons may exist when a particular discouraged behavior is acceptable or even useful; however, the full implications must be understood and carefully weighed before implementing any behavior described by this keyword.

may: a definition or behavior is truly optional.

General Terminology

array: a (usually fixed-size) multidimensional container of items of the same type and size.

axis: an array dimension.

branch cut: a curve in the complex plane across which a given complex function fails to be continuous.

broadcast: automatic (implicit) expansion of array dimensions to be of equal sizes without copying array data for the purpose of making arrays with different shapes have compatible shapes for element-wise operations.

compatible: two arrays whose dimensions are compatible (i.e., where the size of each dimension in one array is either equal to one or to the size of the corresponding dimension in a second array).

element-wise: an operation performed element-by-element, in which individual array elements are considered in isolation and independently of other elements within the same array.

matrix: a two-dimensional array.

rank: number of array dimensions (not to be confused with the number of linearly independent columns of a matrix).

shape: a tuple of N non-negative integers that specify the sizes of each dimension and where N corresponds to the number of dimensions.

singleton dimension: a dimension whose size is one.

vector: a one-dimensional array.