koszulExtension -- creates the Koszul extension complex of a map

• Usage:

  MM = koszulExtension(FF,BB,psi1,ff)

• Inputs:
  • FF, a complex, resolution over S
  • BB, a complex, two-term complex BB_1-->BB_0
  • psi1, a matrix, from BB_1 to FF_0
  • ff, a matrix, regular sequence annihilating the module resolved by FF
• Outputs:
  • MM, a complex, the mapping cone of the induced map B[-1]\otimes KK(ff) to W extending psi