code: public static MatrixFunction asConstFunction(final double arg) {
          return new MatrixFunction() {
              @Override
              public double evaluate(int i, int j, double value) {
                  return arg;
              }
          };
      }
docs: Creates a const function that evaluates it's argument to given {@code value}.
  
  @param arg a const value
  
  @return a closure object that does {@code _}