# Singular

#### D.14.1.44 printMoebius

Procedure from library `arr.lib` (see arr_lib).

Usage:
printMoebius(A); arr A

Return:
[] displays the moebius values of all the flats in the poset

Remarks:
Mainly used for debugging.

Example:
 ```LIB "arr.lib"; ring R = 0,(x,y,z,t),dp; arr A = arrBraid(4); arrposet P = arrLattice(A); ==> ==> ==> === Computing poset === ==> ==> ==> rank 2: found 7 flats in 0s ==> rank 3: found 1 flats in 0s ==> ==> ==> Matrix tests: 38 P; ==> Given Arrangement: ==> _[1]=x-y ==> _[2]=x-z ==> _[3]=x-t ==> _[4]=y-z ==> _[5]=y-t ==> _[6]=z-t ==> ==> Corresponding poset: ==> ====== rank 1: 6 flats ====== ==> (1), (2), (3), (4), (5), (6), ==> ====== rank 2: 7 flats ====== ==> (1,2,4), (1,3,5), (1,6), (2,3,6), (2,5), (3,4), (4,5,6), ==> ====== rank 3: 1 flats ====== ==> (1,2,3,4,5,6), ==> ====== rank 4: 0 flats ====== ==> ==> //As you can see the values are not calculated yet: printMoebius(P); ==> Moebius values: ==> ====== rank 1: 6 flats ====== ==> (-1), (-1), (-1), (-1), (-1), (-1), ==> ====== rank 2: 7 flats ====== ==> (0), (0), (0), (0), (0), (0), (0), ==> ====== rank 3: 1 flats ====== ==> (0), ==> ====== rank 4: 0 flats ====== ==> P = moebius(P); //Now all entries are initialized: printMoebius(P); ==> Moebius values: ==> ====== rank 1: 6 flats ====== ==> (-1), (-1), (-1), (-1), (-1), (-1), ==> ====== rank 2: 7 flats ====== ==> (2), (2), (1), (2), (1), (1), (2), ==> ====== rank 3: 1 flats ====== ==> (-6), ==> ====== rank 4: 0 flats ====== ==> ```