length GradedModule -- length of a graded module

length GradedModule -- length of a graded module

Synopsis:

Function: length -- length

Input:

an instance of class GradedModule.

Output:

an instance of class ZZ.

The length of a graded module is the difference between the largest and smallest indices of occupied spots. Chain complexes are graded modules, so this function applies to them, too.

i1 : R = QQ[x..z];

i2 : C = res coker vars R



      1      3      3      1

o2 = R  <-- R  <-- R  <-- R  <-- 0

                                  

     0      1      2      3      4



o2 : ChainComplex

i3 : length C



o3 = 3

Code:

     -- ../../../Macaulay2/m2/gradedmodules.m2:22-24
     length GradedModule := (M) -> (
          s := spots M;
          if #s === 0 then 0 else max s - min s)