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Tracks and c°Before going further, we'll need the definition of an "entity". I'll have more to say on that topic later, but for now let's take it as is.
Apart from the name, nothing weird here. Robert is not going to speak of ghosts or alien entities.
Robert_Mauriès, p.2 wrote:Une entité de G est l’ensemble formé de tous les candidats d’une même case, ou de tous les candidats de même occurrence d’une même zone
Translator = me wrote:An entity is the set of candidates for the same cell or the set of candidates with the same number in the same unit"
(I've translated to more usual Sudoku vocabulary.)
In my vocabulary, an "entity" is merely the content of a 2D-cell or CSP-Variable.
Robert_Mauriès, p.3 wrote:Définitions 2-1
1) Une piste P(Ak ) issue d’un candidat Ak est l’ensemble des candidats Ai ∈ G que l’on placerait avec les TR si Ak était placé.
2) Une antipiste P’(Ak ) issue d’un candidat Ak est l’ensemble des candidats Ai ∈ G que l’on placerait avec les TR si Ak était éliminé de la grille.
On dit que P’(Ak ) est l’antipiste de la piste P(Ak ).
3) Une piste P(E) issue d’un ensemble de candidats E est l’ensemble des candidats Ai communs à toutes les pistes issues de tous les candidats Ak ∈ E .
On a donc P(E) = ∩ E P(Ak ), soit P(E) ⊆ P(Ak ) ∀k.
4) Une antipiste P’(E) issue d’un ensemble de candidats E est l’ensemble des candidats Ai que l’on placerait avec les TR si on éliminait tous les candidats A k ∈ E .
On dit que P’(E) est l’antipiste de la piste P(E).
Translator = me wrote:Definitions 2.1
1) The track P(Ak) based on a candidate Ak is the set of candidates that would be asserted as true by the TR if Ak was true.
2) The antitrack P'(Ak) based on a candidate Ak is the set of candidates that would be asserted as true by the TR if Ak was false.
3) The track P(E) based on a set of candidates E is the set of candidates common to all the tracks P(Ak), Ak ∈ E.
We therefore have P(E) = ∩E P(Ak ), i.e. P(E) ⊆ P(Ak ) ∀k.
4) The antitrack P'(E) based on a set of candidates E={Ak...} is the set of candidates that would be asserted as true by the TR if all the Ak ∈ E were false.
We say that P'(E) is the anti track of the track P(E).
Edit: I've improved the translation of 4) so that there is no ambiguity about the meaning of "true")
Nothing to say here (except always the same remarks about "the TR"). Just a bunch of definitions. Whether they are useful will be sen later.
Ah, yes, something more; just a remark on the fly: the end of definition 3 -
"P(E) = ∩E P(Ak ), i.e. P(E) ⊆ P(Ak ) ∀k" - must be a new fundamental theorem in Set Theory, making Robert a potential candidate for a Fields Medal.
Starting from today, P(E) = ∩E P(Ak ) is equivalent to P(E) ⊆ P(Ak ) ∀k; you don't need to prove the reverse inclusion.
That'll make a lot of students happy; they can replace half of their home work by playing with their Nintendo.
Sometimes, you think something is a fly, but it turns out to be a hornet.
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