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Maps as objects: inversion, homothety, Moebius maps, with composition, inverse and the image of a set

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Avaliação

Dificuldade
5/5
Tempo estimado
Mais de uma semana
Facilidade para iniciantes
35/100
Tipo de issue
Funcionalidade
Clareza
Razoavelmente clara
Status de atividade
Ativa
Stack de tecnologia
csharp
Domínio
backend

Direção de pesquisa

Start with the node model and the related issues #495, #330, #217, and #2132; the issue says map objects need domain, inverse, fixed points, composition, set images, and a point at infinity. Check how image(f, z in S) is represented and why membership is undecided for 2z + 1 on the unit circle. Done means maps can be composed, inverted and applied to sets, with inversion mapping a circle to a decided circle result.

Escrita pelo modelo de indexação a partir do texto da issue.

Descrição

Chapter IV of Modenov's Problems in Geometry (#2131) is about inversion, and Chapters I–III use homotheties, rotations, reflections, similarities and Möbius maps throughout. The book composes them, inverts them, finds their fixed points, and maps circles and regions through them.

What AngouriMath has: apply(lambda(z, (a*z + b)/(c*z + d)), w) works, and lambdas compose numerically. What it lacks:

  • a map with a domain, an inverse and fixed points;
  • composition as an operation on maps that can be simplified;
  • the image of a set under a map. image(f, z in S) parses, but membership in it is undecided even for 2z + 1 on the unit circle;
  • the point at infinity, without which an inversion is not a bijection (#217).

Wanted, for v3:

  • maps as objects, with builders such as inversion(O, k) and homothety(O, k), that can be composed, inverted and applied to sets;
  • an inversion that sends a circle to a circle as a decided result.

The builders could be tried in 2.8 as lambdas, but the object needs the node model. A lambda applied to a vector is wrong today (#2132).

Related: #495 (lambdas as entities), #330 (image sets), #217 (complex infinity).

Linguagem predominante
C#
Estrelas
831
Forks
79
Merge médio
1h 14min
PRs com merge (30d)
522

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