├── OUTPUT-Recursive-descent-parser.JPG
├── README.md
└── Recursive-descent-parser.py


/OUTPUT-Recursive-descent-parser.JPG:
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https://raw.githubusercontent.com/Abhishekmishra-17/Recursive-Descent-Parser-using-python/HEAD/OUTPUT-Recursive-descent-parser.JPG


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/README.md:
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 1 | # Recursive-Descent-Parser-using-python
 2 | This is program of recursive descent parser using Python programming language.
 3 | 
 4 | # Recursive Descent Parser:
 5 | It is a kind of Top-Down Parser. A top-down parser builds the parse tree from the top to down, starting with the start non-terminal. A Predictive Parser is a special case of Recursive Descent Parser, where no Back Tracking is required.
 6 | By carefully writing a grammar means eliminating left recursion and left factoring from it, the resulting grammar will be a grammar that can be parsed by a recursive descent parser.
 7 | 
 8 | 
 9 | **Here 'i' is Epsilon or any terminals symbol.**
10 | 
11 | For Recursive Descent Parser, we are going to write one program for every variable.
12 | 
13 | 
14 | **Any suggestion regarding this program is helpful for me**
15 | 


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/Recursive-descent-parser.py:
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 1 | print("Recursive Desent Parsing For following grammar\n")
 2 | print("E->TE'\nE'->+TE'/@\nT->FT'\nT'->*FT'/@\nF->(E)/i\n")
 3 | print("Enter the string want to be checked\n")
 4 | global s
 5 | s=list(input())
 6 | global i
 7 | i=0
 8 | def match(a):
 9 |     global s
10 |     global i
11 |     if(i>=len(s)):
12 |         return False
13 |     elif(s[i]==a):
14 |         i+=1
15 |         return True
16 |     else:
17 |         return False
18 | def F():
19 |     if(match("(")):
20 |         if(E()):
21 |             if(match(")")):
22 |                 return True
23 |             else:
24 |                 return False
25 |         else:
26 |             return False
27 |     elif(match("i")):
28 |         return True
29 |     else:
30 |         return False
31 | def Tx():
32 |     if(match("*")):
33 |         if(F()):
34 |             if(Tx()):
35 |                 return True
36 |             else:
37 |                 return False
38 |         else:
39 |             return False
40 |     else:
41 |         return True
42 | def T():
43 |     if(F()):
44 |         if(Tx()):
45 |             return True
46 |         else:
47 |             return False
48 |     else:
49 |         return False
50 | def Ex():
51 |     if(match("+")):
52 |         if(T()):
53 |             if(Ex()):
54 |                 return True
55 |             else:
56 |                 return False
57 |         else:
58 |             return False
59 |     else:
60 |         return True
61 | def E():
62 |     if(T()):
63 |         if(Ex()):
64 |             return True
65 |         else:
66 |             return False
67 |     else:
68 |         return False
69 | if(E()):
70 |     if(i==len(s)):
71 |         print("String is accepted")
72 |     else:
73 |          print("String is not accepted")
74 |     
75 | else:
76 |     print("string is not accepted")
77 | 


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