anchor.diff:   (jacobi-2d
     (jacobi-2d domain)))
   
  -;;; Finally, let's have a glimpse at the Petalisp intermediate
  -;;; representation of Jacobi's algorithm.
  +;;; Finally, let's have a glimpse at the Petalisp data flow representation
  +;;; of Jacobi's algorithm and the corresponding IR.
   
   (petalisp.graphviz:view
  - (first
  -  (petalisp.ir:ir-from-lazy-arrays
  -   (list
  -    (jacobi-2d
  -     (jacobi-2d domain))))))
  + (list
  +  (jacobi-2d
  +   (jacobi-2d domain))))
  +
  +(petalisp.graphviz:view
  + (petalisp.ir:ir-from-lazy-arrays
  +  (list
  +   (jacobi-2d
  +    (jacobi-2d domain)))))
  
positive.code:   (let ((interior (interior grid)))
      (fuse*
       grid
       (α #'* 0.25
          (α #'+
             (reshape grid (τ (i j) ((1+ i) j)) interior)
             (reshape grid (τ (i j) ((1- i) j)) interior)
  
negative.code: 
  (in-package #:petalisp.examples.getting-started)
  
  (defun present (&rest arrays)
    (format t "~{~& => ~A~}"
            (multiple-value-list
             (apply #'compute arrays))))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  