i4 : f vars R
 ker (1) called with OptionTable: OptionTable{SubringLimit => infinity}
 ker (1) returned CacheFunction: *a cache function*
 ker (1) called with Matrix:  a b c a b c 
 ker (1) returned Module: image {1}  1 0 0 b 0 c 
 {1}  0 1 0 a c 0 
 {1}  0 0 1 0 b a 
 {1}  1 0 0 0 0 0 
 {1}  0 1 0 0 0 0 
 {1}  0 0 1 0 0 0 
assert( ker(map(R^1,R^{6:{1}},{{a, b, c, a, b, c}})) === (image(map(R^{6:{1}},R^{3:{1}, 3:{2}},{{1, 0, 0, b, 0, c}, {0, 1, 0, a, c, 0}, {0, 0, 1, 0, b, a}, {1, 0, 0, 0, 0, 0}, {0, 1, 0, 0, 0, 0}, {0, 0, 1, 0, 0, 0}}))))
o4 = image {1}  1 0 0 b 0 c 
{1}  0 1 0 a c 0 
{1}  0 0 1 0 b a 
{1}  1 0 0 0 0 0 
{1}  0 1 0 0 0 0 
{1}  0 0 1 0 0 0 
6
o4 : Rmodule, submodule of R
