sum(ChainComplex) -- direct sum of the components of a chain complex

i1 : R = ZZ/101[a..d];

i2 : C = res coker vars R

      1      4      6      4      1
o2 = R  <-- R  <-- R  <-- R  <-- R  <-- 0
                                         
     0      1      2      3      4      5

o2 : ChainComplex

i3 : sum C

      16
o3 = R

o3 : R-module, free, degrees {0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4}

i4 : degrees oo

o4 = {{0}, {1}, {1}, {1}, {1}, {2}, {2}, {2}, {2}, {2}, {2}, {3}, {3}, {3},
     ------------------------------------------------------------------------
     {3}, {4}}

o4 : List