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descentSet -- the descent set of a permutation

Description

Given a permutation in 1-line notation, lists the location of its descents, i.e., the least $i$ so that $w_{i+1}<w_i$.

i1 : w = {7,2,5,8,1,3,6,4}

o1 = {7, 2, 5, 8, 1, 3, 6, 4}

o1 : List
 
i2 : descentSet w

o2 = {1, 4, 7}

o2 : List

Ways to use descentSet:

  • descentSet(List)

For the programmer

The object descentSet is a method function.

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/MatrixSchubert/permutationMethodsDOC.m2:102:0.