equal
deleted
inserted
replaced
16 \begin{center} |
16 \begin{center} |
17 $r ::= \varnothing \;|\; \epsilon \;|\; c \;|\; r_1 + r_2 \;|\; r_1 \cdot r_2 \;|\; r^*$ |
17 $r ::= \varnothing \;|\; \epsilon \;|\; c \;|\; r_1 + r_2 \;|\; r_1 \cdot r_2 \;|\; r^*$ |
18 \end{center} |
18 \end{center} |
19 |
19 |
20 \item Define the function $zeroable$ which takes a regular expression as argument |
20 \item Define the function $zeroable$ which takes a regular expression as argument |
21 and returns an integer. The function should satisfy the following property: |
21 and returns a boolean.\footnote{In an earlier version there was an error.} The |
|
22 function should satisfy the following property: |
22 \begin{center} |
23 \begin{center} |
23 $zeroable(r)$ \;if and only if\; $L(r) = \varnothing$ |
24 $zeroable(r)$ \;if and only if\; $L(r) = \varnothing$ |
24 \end{center} |
25 \end{center} |
25 |
26 |
26 \item Define the tokens and regular expressions for a language |
27 \item Define the tokens and regular expressions for a language |