-- -*- M2-comint -*- hash: 5268845107301320519

i1 : codimBsInv = (m) -> (
        -- input: m, the list of projective degrees of a birational map
        -- output: the codimension of the base locus of the inverse map
        k:=#m -1; z:=m_k; d:=floor(m_(k-1)/z);
        for i from 2 to k do if z*d^i - m_(k-i) > 0 then return i;
     );

i2 : phi = toMap trim minors(2,genericSymmetricMatrix(QQ[x_0..x_5],3))

                                    2                                    2                       2
o2 = map (QQ[x ..x ], QQ[x ..x ], {x  - x x , x x  - x x , x x  - x x , x  - x x , x x  - x x , x  - x x })
              0   5       0   5     4    3 5   2 4    1 5   2 3    1 4   2    0 5   1 2    0 4   1    0 3

o2 : RingMap QQ[x ..x ] <-- QQ[x ..x ]
                 0   5          0   5

i3 : codimBsInv projectiveDegrees phi

o3 = 3

i4 : 
