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Tableaux

A Young diagram, or Ferrers diagram, is a collection of boxes, or cells, arranged in left--justified rows, with a weakly decreasing number of boxes in each row. Listing the number of boxes in each row gives a partition (its shape) of n, where n is the total number of boxes in the diagram. Conversely, each partition corresponds to a unique Young diagram. A filling of a Young diagram places a positive integer in each box. A Young tableau, or simply tableau, is a filling which has i) weakly increasing entries across each row, and ii) strictly increasing entries down each column. Flipping a diagram over its main diagonal gives the Conjugate diagram, its shape being the ConjugatePartition of the original shape.

A Skew diagram or Skew Shape is the diagram obtained by removing a smaller Young diagram from a larger on that contains it. A Skew tableau is a filling on a skew diagram obeying the same restrictions on entries.

Every tableau has an outer shape and a skew shape, both partitions. Calculus of the tableau takes place by way of standard row insertion and Jeu De Taquin algorithms.

Tableau(s) : SeqEnum -> Tableau
s is a sequence of sequences of positive integers which are the entries of the tableau. To form a skew tableau, zeros are to be used to denote skew entries.
ReverseFilling(P1, P2) : SeqEnum,SeqEnum -> Tableau
Returns a standard skew tableau of outer shape P1 and skew shape P2, entries are from biggest to smallest right to left bottom to top.

ReverseFilling(P1) : SeqEnum -> Tableau
Returns a (non--skew) standard tableau of outer shape P1, entries are from biggest to smallest right to left and bottom to top.
WordToTableau(w) : SeqEnum -> Tableau
Each word corresponds to a unique tableau. This tableau is obtained through row insertion of w (from the left) into the empty tableau.
HookLength(P, i, j) : Tableau,RngIntElt,RngIntElt -> RngIntElt
Each Partition corresponds to a Young diagram, and each position on that diagram has an associated hook. The hook consists of all boxes in its row to the right of the box, and all boxes in its column below the hook. HookLength returns the length of the hook of the (i, j)th position of the Young Diagram for the partition P.

NumberOfStandardTableaux(P) : SeqEnum -> RngIntElt
Returns the number of standard tableau constructible on the shape described by the partition P.
NumberOfTableauxOnAlphabet(P, m) : SeqEnum,RngIntElt -> RngIntElt
Returns the number of tableau constructible on the shape described by the partition P, and with entries coming from [m].
DiagonalSum(t1, t2) : Tableau,Tableau -> Tableau
The DiagonalSum of two tableau is formed by first having a rectangle of empty squares, with the same number of columns as t1 and the same number of rows as t2. Then t1 is attached below the rectangle and t2 attached to right of it.

JeuDeTaquin(~t) : Tableau ->
JeuDeTaquin(t) : Tableau -> Tableau
Rectify(~t) : Tableau ->
Rectify(t) : Tableau -> Tableau
If t is skew then it will be rectified using Jeu de Taquin to remove any skewed entries.

RowInsert(~t, i) : Tableau,RngIntElt ->
RowInsert(t, i) : Tableau,RngIntElt -> Tableau
The value i is row inserted into tableau t using the standard row insertion algorithm.

RowInsert(~t, w) : Tableau,SeqEnum ->
RowInsert(t, w) : Tableau,SeqEnum -> Tableau
The word w is row inserted left to right into the tableau t using the standard row insertion algorithm.
Content(t) : Tableau -> SeqEnum
The content of a tableau is a sequence where the ith position denotes the number of occurrences of i in the tableau.
Word(t) : Tableau -> SeqEnum
RowWord(t) : Tableau -> SeqEnum
Returns the row word of the tableau, reading entries left to right, bottom to top.

ColumnWord(t) : Tableau -> SeqEnum
Returns the column word of tableau t, reading the entries from bottom to top, left to right.
Shape(t) : Tableau -> SeqEnum
OuterShape(t) : Tableau -> SeqEnum
Returns the partition denoting the outer shape of the tableau.
SkewShape(t) : Tableau -> SeqEnum
Returns the partition (with trailing zeros) of the skew shape of the tableau.
Weight(t) : Tableau -> RngIntElt
Returns the weight of the tableau, which is the number of (non--skew) entries
SkewWeight(t) : Tableau -> RngIntElt
Returns the skew weight of the tableau, which is the number of skew entries
NumberOfRows(t) : Tableau -> RngIntElt
Nrows(t) : Tableau -> RngIntElt
The number of rows in the tableau.
NumberOfSkewRows(t) : Tableau -> RngIntElt
NSrows(t) : Tableau -> RngIntElt
Returns the number of skewed rows in the tableau.
Row(t, i) : Tableau -> SeqEnum
Returns the ith row of tableau t. If tableau is skew, then skewed positions will be filled with zeros

Rows(t) : Tableau -> SeqEnum
Returns an sequence of sequence's which are the rows of the tableau (skewed positions filled with zeros)
FirstRowEntry(t, i) : Tableau,RngIntElt -> RngIntElt
Returns the index of the first non--skew entry of the ith row. If the row has no non--skew entries then the index will be 1 greater than the length of the row, ie out of bounds.
LastRowEntry(t, i) : Tableau,RngIntElt -> RngIntElt
RowLength(t, i) : Tableau,RngIntElt -> RngIntElt
Returns the index of the last entry of the tableau in the ith row, which is the length of the ith row.
FirstColumnEntry(t, j) : Tableau,RngIntElt -> RngIntElt
Returns the index of the first non--skew entry of the jth column. If the column has no non--skew entries then the index will be 1 greater than the length of the column, ie out of bounds.
LastColumnEntry(t, j) : Tableau,RngIntElt -> RngIntElt
ColumnLength(t, j): Tableau,RngIntElt -> RnfIntElt
Returns the index of the last entry of the tableau in the jth column, which is the length of the jth column.
RowSkewLength(t, i) : Tableau,RngIntElt -> RngIntElt
Returns the length of the skewed portion of the ith row (zero if no skewed portion)
ColumnSkewLength(t, j) : Tableau,RngIntElt -> RngIntElt
Returns the length of the skewed portion of the jth column (zero if no skewed portion)
IsStandard(t) : Tableau -> BoolElt
Returns true if t is a standard tableau. ie has entries 1 ... n, where n is the weight of the tableau. No repeats are allowed.
IsSkew(t) : Tableau -> BoolElt
Returns true if t is a skew tableau.
IsLittleWoodRichardsonSkew(t) : Tableau -> BoolElt
Returns true if t is a Littlewood--Richardson Skew tableau, i.e. if the content of t forms a reverse lattice word.
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