KERNEL _ _ _ _ _ _ _ _ _ _ _ _ type

A kernel is a form that cannot be modified further by the REDUCE canonical simplifier. Scalar variables are always kernels. The other important class of kernels are operators with their arguments. Some examples should help clarify this concept:

        Expression                     Kernel?

          x                              Yes
          varname                        Yes
          cos(a)                         Yes
          log(sin(x**2))                 Yes
          a*b                            No
          (x+y)**4                       No
          matrix-identifier              No

Many REDUCE operators expect kernels among their arguments. Error messages result from attempts to use non-kernel expressions for these arguments.