HomologicalShiftIdeals - A Macaulay2 package for computing the homological shift ideals of a monomial ideal of a polynomial ring

[Antonino-Ficarra]

A Macaulay2 package for computing the homological shift ideals of a monomial ideal of a polynomial ring

[d-torrance]

Thanks for your contribution!

Both new package files should have the .m2 file extension.

[Antonino-Ficarra]

Thanks for your contribution!

Both new package files should have the .m2 file extension.

Ok, sorry. I added the ".m2" extension.

[Antonino-Ficarra]

I forgot a semicolon

[Antonino-Ficarra]

I forgot some semicolons

[d-torrance]

Those semicolons don't really matter. The only time when you definitely need semicolons is when a function body contains multiple statements:

f = x -> (
  statement1;
  statement2;
  statement3;
  statement4)

The other time is when you want to suppress the output when interacting directly with Macaulay2.

[d-torrance]

This is the same map that was constructed for toMultidegree, but you're applying it to an ideal instead of a ring element. Perhaps you could extract this code into a helper function that both methods could call? (DRY principle when programming -- don't repeat yourself!)

[Antonino-Ficarra]

Fixed a small error

[d-torrance]

There was a conflict with =distributed-packages since another package was recently added, so I fixed that and force-pushed. I also added MatchingPowers to that file since it was missing.

[d-torrance]

There are still a number of examples that are producing errors:

-- -*- M2-comint -*- hash: 2495905948357533320

i1 : S = QQ[x_1..x_4];

i2 : I = ideal(x_1*x_2,x_3^2,x_4^2);

o2 : Ideal of S

i3 : matchingPower(I,2)
stdio:3:13:(3): error: expected ideals for the same ring
-- -*- M2-comint -*- hash: 11433797791073189326

i1 : S = QQ[x_1..x_4];

i2 : I = ideal(x_1*x_2,x_3^2,x_4^2);

o2 : Ideal of S

i3 : J = ideal(x_1*x_3,x_2);

o3 : Ideal of S

i4 : matchingProduct(I,J)
stdio:4:15:(3): error: expected ideals for the same ring
-- -*- M2-comint -*- hash: 4326397003292871051

i1 : S = QQ[x_1..x_4];

i2 : I = ideal(x_1*x_2,x_3^2,x_4^2);

o2 : Ideal of S

i3 : monomialGrade I
stdio:3:13:(3): error: expected ideals for the same ring
-- -*- M2-comint -*- hash: 4326397004548556957

i1 : S = QQ[x_1..x_4];

i2 : I = ideal(x_1*x_2,x_3^2,x_4^2);

o2 : Ideal of S

i3 : gFunction I
stdio:3:9:(3): error: expected ideals for the same ring
-- -*- M2-comint -*- hash: 4025997899046634755

i1 : S = QQ[x_1..x_5];

i2 : I = ideal(x_1,x_2,x_3,x_4)*ideal(x_3,x_4,x_5);

o2 : Ideal of S

i3 : admissibleOrder I

                   2                     2
o3 = {x x , x x , x , x x , x x , x x , x , x x , x x , x x , x x }
       1 3   2 3   3   1 4   2 4   3 4   4   1 5   2 5   3 5   4 5

o3 : List

i4 : S = QQ[x,y];

i5 : I = ideal(x^2,y^2);

o5 : Ideal of S

i6 : admissibleOrder I
stdio:6:15:(3): error: the ideal does not have linear quotients

[d-torrance]

@Antonino-Ficarra: Have you had a chance to look at the examples that are failing?