NAME ____________________________________________

CS 420/520 Theory of Computation, Spring 2019 at Indiana State University, taught by Jeff Kinne
Quiz 6 - regular languages still

Points - each part is graded as 1 point, half credit is possible.

1) If the following language is regular, give an RE, DFA, or NFA for the language.
   If it is not regular, prove it is not regular using the pumping lemma.

   L = {strings of 0's and 1's with an even # of 1's and an odd # of 0's}
   In the language:     101, 01010, 11000, 011, 000
   Not in the language: 1000, 0100, 00, 1










2) If the following language is regular, give an RE, DFA, or NFA for the language.
   If it is not regular, prove it is not regular using the pumping lemma.

   L = {strings of 0's and 1's of the form 0^n 1^m 0^n | m,n >= 0}
   In the language:     00100, 111, 010, 00001110000
   Not in the language: 0100, 00111000















3) If the following language is regular, give an RE, DFA, or NFA for the language.
   If it is not regular, prove it is not regular using the pumping lemma.

   L = {w | the even positions in w form a string of a's and b's with an even # of a's, and
            the odd positions in w form a string of a's and b's that begin and end with b}
   In the language:     ab ab bb ba bb, ab ba aa bb, ab ab
   Not in the language: ab bb, aa ab, ab aa










4) Complete the Python3 code to determine if a string input by the user is a valid math
   expression involving positive integers, +, *, -, /
   Note -     in the language: 1234+234-234*234, 1234, 2*4
        - not in the language: (23+23)/234, -234, hello, 234k, pi, 2.3, 2 + 3


s = input('Please enter a valid math expression: ')
import re




match = re.match('                                                                    ', s)



if match: print('Valid!')
else: print('Not valid. :(')











5) Complete the Python3 code to determine if a string input by the user is a valid C variable
   name that has the following rules - must start with a letter; can contain letters, digits,
   and underscore
   Note -     in the language: hello123, hello, h_, hello_there, HI
        - not in the language: hello.one, _hello, 234hello

s = input('Please enter a valid variable name: ')
import re




match = re.match('                                                                    ', s)



if match: print('Valid!')
else: print('Not valid. :(')