kernel -- kernel of a ringmap, matrix, or chain complex

Ways to use kernel :

• kernel(ChainComplexMap) -- kernel of a chain complex map
• kernel(GradedModuleMap) -- see kernel(ChainComplexMap) -- kernel of a chain complex map
• kernel(Matrix) -- kernel of a matrix
• kernel(RingElement) -- see kernel(Matrix) -- kernel of a matrix
• kernel(RingMap) -- kernel of a ringmap
• kernel(SheafMap) (missing documentation)

For the programmer

The object kernel is a method function with options.