1554 machine that does a derivative of regular expressions

  1554 

  1555 on all strings simultaneously, taking 

  1556 the bits by going throught the regular expression tree

  1557  structure in a depth first manner, regardless of whether

  1558  the part being traversed is nullable or not.

  1559  It put all possible bits that can be produced on such a traversal

  1560  into a set.

  1561  For example, if we are given the regular expression 

  1562 $((a+b)(c+d))^*$, the tree structure may be written as\\

  1563 \\

  1564 \\

  1565 \\

  1566 \\

  1567 \\

  1568 \\

  1569 \begin{center}

  1570 \begin{tikzpicture}

  1571 \tikz[tree layout]\graph[nodes={draw, circle}] {

  1572 * -> 

  1573     {@-> {

  1574     {+1 ->

  1575         {a , b}

  1576         },

  1577     {+ ->

  1578         {c , d }

  1579         }

  1580         }

  1581     }

  1582 };