Question

Write a python parser program that uses the following context free grammar

<S> → ‘a’ <S> ‘b’

<S> → ‘c’

Test your parser with c, acb, aacbb, λ, ca, ab,acbb, aacb, and bca(λ represents a null string)

Answer 1

Code

s = input('Enter String: ')
s = list(s)
buff = ['S']
print('Input',s,' Buffer',buff)
while s!=[]:
if buff==[]:
break
if s[0]==buff[0]:
print('Match ',s.pop(0))
buff.pop(0)
elif buff[0]=='S':
buff.pop(0)
if s[0]=='a':
buff=['a','S','b']+buff
print('Using Production S->aSb')
elif s[0]=='c':
buff=['c']+buff
print('Using Production S->c')
else:
print('Error in parsing!! No Production found!!')
break;
else:
print('Error in parsing!! Mismatch found')
break;
print('Input',s,' Buffer',buff)
if s==[] and buff==[]:
print('Parsing complete!!')
else:
print('Parsing failed!!')