homomorphism' -- get the element of Hom from a homomorphism

i1 : R = QQ[x,y,z]

o1 = R

o1 : PolynomialRing

i2 : f = vars R ++ vars R

o2 = | x y z 0 0 0 |
     | 0 0 0 x y z |

             2       6
o2 : Matrix R  <--- R

i3 : g = homomorphism' f

o3 = {-1} | x |
     {-1} | 0 |
     {-1} | y |
     {-1} | 0 |
     {-1} | z |
     {-1} | 0 |
     {-1} | 0 |
     {-1} | x |
     {-1} | 0 |
     {-1} | y |
     {-1} | 0 |
     {-1} | z |

             12       1
o3 : Matrix R   <--- R

i4 : target g === Hom(source f, target f)

o4 = true

i5 : f' = homomorphism g

o5 = | x y z 0 0 0 |
     | 0 0 0 x y z |

             2       6
o5 : Matrix R  <--- R

i6 : f === f'

o6 = true