SG::Perm2Desc --
computes the list of descents of a permutation
Call(s)
SG::Perm2Desc(perm <,nb,maj,comaj>)
Parametersperm | - | any list denoting a permutation |
nb | - | only counts objects |
maj | - | sum of descent positions |
comaj | - | sum of all values |
IntroductionThe SG::Perm2Desc function computes the list of descents of the
permutation perm, i.e. the list of positions i,
such that perm[i] >
perm[i+1].
When called with the second argument maj, it returns the
sum of the descent positions.
When called with the second argument comaj, it returns the
sum of all values (n - descent position), where n is
equal to nops(perm).
Example 1>> muEC::SG::Perm2Desc( [3,1,4,2,6,5,7] );
[1, 3, 5]
>> muEC::SG::Perm2Desc( [3,1,4,2,6,5,7], nb );
3
>> muEC::SG::Perm2Desc( [3,1,4,2,6,5,7], maj );
9
>> muEC::SG::Perm2Desc( [3,1,4,2,6,5,7], comaj );
12
Related FunctionsMuPAD Combinat, an open source algebraic combinatorics package