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AbstractBlockArray documentation enhancement #456

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2a35639
feat(docs): Imitate the standard library docs strings for AbstractArray
kunzaatko Apr 10, 2025
10b8a9f
feat(docs): Add documentation anchors in the index page
kunzaatko Apr 10, 2025
79bf530
chore(docs): Format tables and fix column headers
kunzaatko Apr 10, 2025
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4 changes: 2 additions & 2 deletions docs/src/index.md
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Expand Up @@ -4,9 +4,9 @@

[![Build Status](https://travis-ci.org/JuliaArrays/BlockArrays.jl.svg?branch=master)](https://travis-ci.org/JuliaArrays/BlockArrays.jl) [![codecov](https://codecov.io/gh/JuliaArrays/BlockArrays.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaArrays/BlockArrays.jl)

A block array is a partition of an array into multiple blocks or subarrays, see [wikipedia](https://en.wikipedia.org/wiki/Block_matrix) for a more extensive description. This package has two purposes. Firstly, it defines an interface for an `AbstractBlockArray` block arrays that can be shared among types representing different types of block arrays. The advantage to this is that it provides a consistent API for block arrays.
A block array is a partition of an array into multiple blocks or subarrays, see [wikipedia](https://en.wikipedia.org/wiki/Block_matrix) for a more extensive description. This package has two purposes. Firstly, it defines an interface for an [`AbstractBlockArray`](@ref) block arrays that can be shared among types representing different types of block arrays. The advantage to this is that it provides a consistent API for block arrays.

Secondly, it also implements two concrete types of block arrays that follow the `AbstractBlockArray` interface. The type `BlockArray` stores each single block contiguously, by wrapping an `AbstractArray{<:AbstractArray{T,N},N}` to concatenate all blocks – the complete array is thus not stored contiguously. Conversely, a `BlockedArray` stores the full matrix contiguously (by wrapping only one `AbstractArray{T, N}`) and only superimposes a block structure. This means that `BlockArray` supports fast non copying extraction and insertion of blocks, while `BlockedArray` supports fast access to the full matrix to use in, for example, a linear solver.
Secondly, it also implements two concrete types of block arrays that follow [`AbstractBlockArray` interface](@ref abstract_block_array_interface). The type [`BlockArray`](@ref) stores each single block contiguously, by wrapping an `AbstractArray{<:AbstractArray{T,N},N}` to concatenate all blocks – the complete array is thus not stored contiguously. Conversely, a [`BlockedArray`](@ref) stores the full matrix contiguously (by wrapping only one `AbstractArray{T, N}`) and only superimposes a block structure. This means that `BlockArray` supports fast non copying extraction and insertion of blocks, while `BlockedArray` supports fast access to the full matrix to use in, for example, a linear solver.


## Terminology
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22 changes: 10 additions & 12 deletions docs/src/man/abstractblockarrayinterface.md
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the block axis interface.


| Methods to implement | Brief description |
| :---------------------- | :---------------- |
| `blockaxes(A)` | A one-tuple returning a range of blocks specifying the block structure |
| `getindex(A, K::Block{1})` | return a unit range of indices in the specified block |
| `blocklasts(A)` | Returns the last index of each block |
| `findblock(A, k)` | return the block that contains the `k`th entry of `A`
| Methods to implement | Brief description |
| :------------------------- | :--------------------------------------------------------------------- |
| `blockaxes(A)` | A one-tuple returning a range of blocks specifying the block structure |
| `getindex(A, K::Block{1})` | Returns a unit range of indices in the specified block |
| `blocklasts(A)` | Returns the last index of each block |
| `findblock(A, k)` | Returns the block that contains the `k`th entry of `A` |


# The `AbstractBlockArray` interface
# [The `AbstractBlockArray` interface](@id abstract_block_array_interface)

An arrays block structure is inferred from an axes, and therefore every array
is in some sense already a block array:
Expand All @@ -37,10 +36,9 @@ julia> A[Block(1,1)]
```
It is possible to override additional functions to improve speed, however.

| Methods to implement | Brief description |
| :---------------------- | :---------------- |
| **Optional methods** |
| `BlockArrays.viewblock(A, i::Block)` | Specialised non-allocating `X[Block(i...)]`, blocked indexing |
| Optional methods | Default definition | Brief description |
| :----------------------------------- | :------------------------------------------------- | :------------------------------------------------------------ |
| `BlockArrays.viewblock(A, i::Block)` | defined in terms `Base.view` and the block indices | Specialised non-allocating `X[Block(i...)]`, blocked indexing |

For a more thorough description of the methods see the public interface documentation.

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32 changes: 19 additions & 13 deletions src/abstractblockarray.jl
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####################################

"""
abstract AbstractBlockArray{T, N} <: AbstractArray{T, N}

The abstract type that represents a blocked array. Types that implement
the `AbstractBlockArray` interface should subtype from this type.

** Typealiases **
AbstractBlockArray{T, N} <: AbstractArray{T, N}
Supertype for `N`-dimensional block arrays with elements of type `T`. [`BlockedArray`](@ref), [`BlockArray`](@ref) and other types are subtypes of this. See the manual section on the
the `AbstractBlockArray` interface.
"""
abstract type AbstractBlockArray{T,N} <: LayoutArray{T,N} end

* `AbstractBlockMatrix{T}` -> `AbstractBlockArray{T, 2}`
"""
AbstractBlockMatrix{T}
Supertype for two-dimensional block arrays with elements of type `T`. Alias for [`AbstractBlockArray{T,2}`](@ref).
"""
const AbstractBlockMatrix{T} = AbstractBlockArray{T,2}

* `AbstractBlockVector{T}` -> `AbstractBlockArray{T, 1}`
"""
AbstractBlockVector{T}
Supertype for one-dimensional block arrays with elements of type `T`. Alias for [`AbstractBlockArray{T,1}`](@ref).
"""
const AbstractBlockVector{T} = AbstractBlockArray{T,1}

* `AbstractBlockVecOrMat{T}` -> `Union{AbstractBlockMatrix{T}, AbstractBlockVector{T}}`
"""
abstract type AbstractBlockArray{T, N} <: LayoutArray{T, N} end
const AbstractBlockMatrix{T} = AbstractBlockArray{T, 2}
const AbstractBlockVector{T} = AbstractBlockArray{T, 1}
const AbstractBlockVecOrMat{T} = Union{AbstractBlockMatrix{T}, AbstractBlockVector{T}}
AbstractVecOrMat{T}
Union type of [`AbstractBlockMatrix`](@ref) and [`AbstractBlockVector`](@ref).
"""
const AbstractBlockVecOrMat{T} = Union{AbstractBlockMatrix{T},AbstractBlockVector{T}}

block2string(b, s) = string(join(map(string,b), '×'), "-blocked ", Base.dims2string(s))
_block_summary(a) = string(block2string(blocksize(a), size(a)), " ", typeof(a))
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