@kgryte

Description

This RFC proposes achieving ndarray API parity with built-in JavaScript arrays. Built-in JavaScript Array and TypedArray objects have a number of methods for searching, manipulating, sorting, and transforming array data.

The goal of this RFC is to add functional APIs providing equivalent functionality for ndarrays. By providing these APIs, stdlib can offer a powerful toolset using a similar vocabulary and interface design as existing art for working with ndarrays. This should help reduce the barrier to ndarray adoption and encourage their more widespread use.

Note, however, that ndarrays have considerable additional complexity due to their multi-dimensional nature, and, in particular, element-wise iteration requires specialized kernels for handling non-contiguous underlying data.

There does exist precedent in stdlib for such kernels (e.g., ndarray/base/assign, ndarray/base/nullary, and ndarray/base/unary). Those packages also provide C APIs which may or may not be relevant to the functional APIs proposed in this RFC.

What follows is an initial list of Array.prototype.* methods and notes regarding whether an equivalent already exists or what constraints we need to consider when designing ndarray equivalent packages.

Top-level: ndarray/*

• Array.prototype.at

  • ndarray/at

• Array.prototype.entries

  • ndarray/iter/entries

• Array.prototype.every

  • ndarray/every

• Array.prototype.forEach

  • ndarray/for-each

• Array.prototype.map

  • ndarray/map

• Array.prototype.filter

  • ndarray/filter

• Array.prototype.slice

  • ndarray/slice

• Array.prototype.keys

  • ndarray/iter/indices

• Array.prototype.values

  • ndarray/iter/values

• Array.prototype.includes

  • ndarray/includes

• Array.prototype.indexOf

  • blas/ext/index-of

• Array.prototype.find

  • reduction; specify one or more axes (WIP)

• Array.prototype.findIndex

  • blas/ext/find-index

• Array.prototype.lastIndexOf

  • blas/ext/last-index-of

• Array.prototype.some

  • ndarray/any

• Array.prototype.findLast

  • reduction; specify one or more axes

• Array.prototype.findLastIndex

  • blas/ext/find-last-index

• Array.prototype.reverse

  • ndarray/reverse

• Array.prototype.toReversed (WIP)

  • data copy
  • can potentially wrap "base"

• Array.prototype.sort

  • multiple functions for different sorting algorithms.
  • blas/ext/sorthp.

• Array.prototype.toSorted

  • specify one or more axes
  • data copy
  • multiple functions for different sorting algorithms.

• Array.prototype.fill

  • ndarray/fill and ndarray/fill-by
  • ndarray/fill-slice

• Array.prototype.flat

  • ndarray/flatten

• Array.prototype.reduce

  • reduction; specify one or more axes

• Array.prototype.concat (WIP)

  • NumPy: https://numpy.org/doc/stable/reference/generated/numpy.concat.html

• Array.prototype.copyWithin

  • specify axis
  • how would this work for strided arrays?
  • for ideal case, would prefer delegating to array prototype method, as likely faster; for non-ideal case, would need to take special care to avoid overwriting accessed values.
  • Slice + assign?
  • Temporary buffer for when there is overlap.

• Array.prototype.reduceRight

  • reduction; specify one or more axes
  • iterate in reverse direction

• Array.prototype.flatMap

  • ndarray/flatten-by

• Array.prototype.join

  • needs R&D
  • how would dimension separators work? a different separator for each dimension? configurable?

• Array.prototype.pop

  • ndarray/pop

• Array.prototype.push (???)

  • this would essentially be concat along an axis
  • support for broadcasting?
  • would require a data copy, no mutation

• Array.prototype.shift

  • ndarray/shift

• Array.prototype.splice

  • needs R&D
  • would involving slicing, concatenation, and data copy

• Array.prototype.toLocaleString

  • needs R&D

• Array.prototype.toSpliced

  • needs R&D

• Array.prototype.toString

  • just call ndarray.toString()?

• Array.prototype.unshift

  • this would essentially be concat along an axis
  • support for broadcasting?
  • would require a data copy, no mutation

• Array.prototype.with

  • ndarray/with

Base: ndarray/base/*

• Array.prototype.fill

  • ndarray/base/fill

• Array.prototype.forEach

  • ndarray/base/for-each

• Array.prototype.map

  • ndarray/base/map

• Array.prototype.reverse

  • ndarray/base/reverse

• Array.prototype.slice

  • ndarray/base/slice

• Array.prototype.toReversed

  • ndarray/base/to-reversed

• Array.prototype.every

  • ndarray/base/every-by

• Array.prototype.some

  • ndarray/base/any

• Array.prototype.find

  • ndarray/base/find

• Array.prototype.pop

  • ndarray/base/pop

• Array.prototype.shift

  • ndarray/base/shift

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• I have read and understood the Code of Conduct.
• Searched for existing issues and pull requests.
• The issue name begins with RFC:.