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Update CHANGELOG for v1.0.0
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‎CHANGELOG.md

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# Digraphs package for GAP - CHANGELOG
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Copyright (C) 2014-19 by Jan De Beule, Julius Jonušas, James D. Mitchell, Michael Torpey, Wilf A. Wilson et al.
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# CHANGELOG – Digraphs package for GAP
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Copyright © 2014-19 by Jan De Beule, Julius Jonušas, James D. Mitchell, Michael
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Torpey, Wilf A. Wilson et al.
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Licensing information can be found in the LICENSE file.
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Licensing information can be found in the `LICENSE` file.
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## Version 1.0.0 (released 03/10/2019)
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Version 1.0.0!
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DigraphColoring (american spelling) was removed.
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Changed IsEulerian.
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QuotientDigraph is changed.
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This is a major release of the Digraphs package that introduces significant new
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functionality, some changes in behaviour, general improvements, and several
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small bugfixes. With this version, we welcome Reinis Cirpons as a contributor
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to the package.
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### Changed functionality or names
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* Perhaps the most immediately visible change is that the `ViewString` for
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immutable digraphs attempts to show more of the known information about the
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digraph. This will break tests that relied on the previous behaviour, that
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contained only the numbers of vertices and edges.
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* The behaviour of `QuotientDigraph` has been changed so that it no longer
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returns digraphs with multiple edges.
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* `IsEulerianDigraph` would previously return `true` for digraphs
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that are Eulerian when their isolated vertices were removed, which
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contradicted the documentation. `IsEulerianDigraph` now returns `false` for
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_all_ digraphs that are not strongly connected.
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* The type of all digraphs has been renamed from `DigraphType` to
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`DigraphByOutNeighboursType`.
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* The synonym `DigraphColoring` (American-style spelling) for `DigraphColouring`
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was removed.
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### Immutable and mutable digraphs
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Previously, every digraph in the Digraphs package was an immutable,
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attribute-storing digraph. It is now possible to create mutable digraphs.
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Mutable digraphs are not attribute-storing, but they can be altered in place -
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by adding or removing vertices and edges - which, unlike with
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immutable digraphs, does not require a new copy of the digraph to be made.
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This can save time and memory.
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This is particularly useful when one wants to create a digraph, alter the
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digraph in some way, and then perform some computations. One can now typically
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do this with fewer resources by creating a mutable digraph, modifying it in
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place, and then converting it into an immutable digraph (which can store
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attributes and properties), before finally performing the computations.
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Every digraph now belongs to precisely one of the categories `IsMutableDigraph`
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or `IsImmutableDigraph`, according to its mutability. A mutable digraph can be
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converted in-place into an immutable digraph with `MakeImmutable`. The are
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various new and updated functions for creating mutable and immutable digraphs,
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and for making mutable or immutable copies.
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Most digraph-creation functions in the package now accept an optional first
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argument, that can be either `IsMutableDigraph` or `IsImmutableDigraph`. Given
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one of these filters, the function will according create the digraph to be of
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the appropriate mutability. When this is option available, the default is
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always to create an immutable digraph.
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On the whole, for a function in the package that takes a digraph as its argument
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and again returns a digraph, the function now returns a digraph of the same
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mutability as its result, and moreover, given a mutable argument, it converts
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the mutable digraph in-place into the result. However, please consult the
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document to learn the exact behaviour of any specific function.
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Old attributes `Foo` in the package that take and return a single digraph have
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been converted into the operation `Foo`, with a corresponding new attribute,
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`FooAttr`. This means that the getter and setter functions, `HasFoo` and
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`SetFoo`, are renamed to `HasFooAttr` and `SetFooAttr`. See `DigraphReverse`
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for an example. For an immutable (and therefore attribute-storing) digraph,
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calling `Foo` calls `FooAttr` and returns an immutable digraph, which it
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stores, and so the effect is as before. For an mutable digraph, calling `Foo`
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modifies the digraph in-place, which remains mutable.
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### New and extended functions
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The package now includes the following new functions:
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* `AsSemigroup` can produce strong semilattices of groups (i.e. Clifford)
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from semilattice digraphs, groups, and homomorphisms. This functionality was
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added by Finn Smith in
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[PR #161](https://github.com/gap-packages/Digraphs/pull/161).
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* `AutomorphismGroup` and `BlissAutomorphismGroup` can now take an optional third
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argument that specifies an edge colouring for the digraph. In this case, the
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functions return only automorphisms of the digraph that preserve the edge
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colouring (and the vertex colouring, if one is given). This brilliant new
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functionality was added by Finn Smith in
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[PR #186](https://github.com/gap-packages/Digraphs/pull/186).
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* `DegreeMatrix`, `LaplacianMatrix`, and `NrSpanningTrees` were introduced by
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Reinis Cirpons in
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[PR #224](https://github.com/gap-packages/Digraphs/pull/224).
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* `DigraphCartesianProduct` and `DigraphDirectProduct`, along with the
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companion functions `DigraphCartesianProductProjections` and
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`DigraphDirectProductProjections`, were introduced by Reinis Cirpons in
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[PR #228](https://github.com/gap-packages/Digraphs/pull/228).
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* `DigraphMycielskian` was added by Murray Whyte in
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[PR #194](https://github.com/gap-packages/Digraphs/pull/194).
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* `DigraphNrStronglyConnectedComponents` was added by Murray Whyte in
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[PR #180](https://github.com/gap-packages/Digraphs/pull/180).
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* `DigraphOddGirth` was added by Murray Whyte in
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[PR #166](https://github.com/gap-packages/Digraphs/pull/166)
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* `DigraphCore` and `IsDigraphCore` were added by Murray Whyte in PRs
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[#221](https://github.com/gap-packages/Digraphs/pull/221) and
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[#217](https://github.com/gap-packages/Digraphs/pull/217), respectively.
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* `DotHighlightedDigraph` was added by Finn Smith in
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[PR #169](https://github.com/gap-packages/Digraphs/pull/169).
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* `IsCompleteMultipartiteDigraph` was added by [Wilf A. Wilson](http://wilf.me)
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in [PR #236](https://github.com/gap-packages/Digraphs/pull/236).
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* `IsEquivalenceDigraph` was added by [Wilf A. Wilson](http://wilf.me) in
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[PR #234](https://github.com/gap-packages/Digraphs/pull/234) as a synonym for
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`IsReflexiveDigraph and IsSymmetricDigraph and IsTransitiveDigraph`.
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* `IsVertexTransitive` and `IsEdgeTransitive` were added by Graham Campbell
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in [PR #165](https://github.com/gap-packages/Digraphs/pull/165).
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* `PetersenGraph` and `GeneralisedPetersenGraph`
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were added by Murray Whyte in PRs
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[#181](https://github.com/gap-packages/Digraphs/pull/181) and
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[#204](https://github.com/gap-packages/Digraphs/pull/204),
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respectively.
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* `RandomLattice` was added by Reinis Cirpons in
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[PR #175](https://github.com/gap-packages/Digraphs/pull/175).
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### New technical functionality
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* The ability to compile (with the flag `--with-external-bliss`) and use the
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Digraphs package with the system version of `bliss` was added
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by Isuru Fernando in
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[PR #225](https://github.com/gap-packages/Digraphs/pull/225).
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* The ability to compile (with the flag `--with-external-planarity`) and use
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the Digraphs package with the system version of the Edge Addition Planarity
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Suite was added by [James D. Mitchell](http://goo.gl/ZtViV6) in
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[PR #207](https://github.com/gap-packages/Digraphs/pull/207).
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## Version 0.15.4 (released 06/08/2019)
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