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app.py
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app.py
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import sys
from flask import Flask , jsonify,redirect, request,render_template
from flask.helpers import url_for
app = Flask(__name__)
app.config["DEBUG"] = True
# non_terminals = ['A','B','C','D','E','F']
# FIRST = {'A':{'!','a','ds','%'},'B':{'!','a','ds','%'},'C':{'!','a','ds','%'},'D':{'!','a','ds','%'},'E':{'!','a','ds','%'},'F':{'!','a','ds','%'},}
# FOLLOW = {'A':{'v','k','*','#'},'B':{'v','k','*','#'},'C':{'v','k','*','#'},'D':{'v','k','*','#'},'E':{'v','k','*','#'},'F':{'v','k','*','#'},}
no_of_terminals = 0
terminals = []
no_of_non_terminals = 0
non_terminals = []
starting_symbol = "_"
no_of_productions = 0
productions = []
productions_dict = {}
FIRST = {}
FOLLOW = {}
j=0
alter_dict_check = {}
def first(string):
alternatives = []
first_ = set()
if string in non_terminals:
alternatives = productions_dict[string]
for alternative in alternatives:
if alter_dict_check[alternative]!=-1:
first_2 = first(alternative)
first_ = first_ |first_2
elif string in terminals:
first_ = {string}
elif string=='' or string=='@':
first_ = {'@'}
else:
first_2 = first(string[0])
if '@' in first_2:
i = 1
while '@' in first_2:
#print("inside while")
first_ = first_ | (first_2 - {'@'})
#print('string[i:]=', string[i:])
if string[i:] in terminals:
first_ = first_ | {string[i:]}
break
elif string[i:] == '':
first_ = first_ | {'@'}
break
first_2 = first(string[i:])
first_ = first_ | first_2 - {'@'}
i += 1
else:
first_ = first_ | first_2
#print("returning for first({})".format(string),first_)
return first_
def follow(nT):
#print("inside follow({})".format(nT))
follow_ = set()
#print("FOLLOW", FOLLOW)
prods = productions_dict.items()
if nT==starting_symbol:
follow_ = follow_ | {'$'}
for nt,rhs in prods:
#print("nt to rhs", nt,rhs)
for alt in rhs:
for char in alt:
if char==nT:
following_str = alt[alt.index(char) + 1:]
if following_str=='':
if nt==nT:
continue
else:
follow_ = follow_ | follow(nt)
else:
follow_2 = first(following_str)
if '@' in follow_2:
follow_ = follow_ | follow_2-{'@'}
follow_ = follow_ | follow(nt)
else:
follow_ = follow_ | follow_2
#print("returning for follow({})".format(nT),follow_)
return follow_
@app.route("/",methods = ['POST','GET'])
def input_data():
global no_of_terminals,terminals,no_of_non_terminals,non_terminals,starting_symbol,no_of_productions,productions,productions_dict,j,alter_dict_check
global FIRST,FOLLOW
data = {
"starting_symbol":starting_symbol,
"non_terminals":non_terminals,
"FIRST":FIRST,
"FOLLOW":FOLLOW
}
if request.method == 'POST':
no_of_terminals = request.form['not']
terminals = request.form['ts']
no_of_non_terminals = request.form['nont']
non_terminals = request.form['nts']
starting_symbol = request.form['ss']
no_of_productions = request.form['nop']
productions = request.form['ps']
context = {
"no_of_terminals":no_of_terminals,
"terminals":terminals,
"no_of_non_terminals":no_of_non_terminals,
"non_terminals":non_terminals,
"starting_symbol":starting_symbol,
"no_of_productions":no_of_productions,
"productions":productions,
}
terminals = terminals.split(",")
non_terminals = non_terminals.split(",")
productions = productions.split(",")
# print(type(terminals))
# productions_dict = {}
for nT in non_terminals:
productions_dict[nT] = []
# print("\nproductions_dict",productions_dict)
for production in productions:
nonterm_to_prod = production.split("->")
# print("\nNON TERM ",nonterm_to_prod)
alternatives = nonterm_to_prod[1].split("/")
for alternative in alternatives:
productions_dict[nonterm_to_prod[0]].append(alternative)
#print("productions_dict",productions_dict)
for nt in non_terminals:
for i in range(len(productions_dict[nt])):
if nt == productions_dict[nt][i][0]:
alter_dict_check[productions_dict[nt][i]]=-1
# print(f"\nNT : {nt}, string : {productions_dict[nt]}")
else:
alter_dict_check[productions_dict[nt][i]]=1
# print("nonterm_to_prod",nonterm_to_prod)
print("\n \t alternatives dict : ",alter_dict_check)
# return "done"
for non_terminal in non_terminals:
FIRST[non_terminal] = set()
for non_terminal in non_terminals:
FOLLOW[non_terminal] = set()
#print("FIRST",FIRST)
for non_terminal in non_terminals:
j=0
FIRST[non_terminal] = FIRST[non_terminal] | first(non_terminal)
print("FIRST :",FIRST)
# exit()
FOLLOW[starting_symbol] = FOLLOW[starting_symbol] | {'$'}
# print(FOLLOW[starting_symbol])
for non_terminal in non_terminals:
FOLLOW[non_terminal] = FOLLOW[non_terminal] | follow(non_terminal)
for non_terminal in non_terminals:
FIRST[non_terminal] = list(FIRST[non_terminal])
FOLLOW[non_terminal] = list(FOLLOW[non_terminal])
data = {
"starting_symbol":starting_symbol,
"non_terminals":non_terminals,
"productions":productions_dict,
"FIRST":FIRST,
"FOLLOW":FOLLOW
}
print("\nPRODUCTIONS_DICT : ", productions_dict)
# pass
return render_template("app.html", data=data)
else:
data["starting_symbol"] = "_"
no_of_terminals = 0
terminals = []
no_of_non_terminals = 0
non_terminals = []
starting_symbol = "_"
no_of_productions = 0
productions = []
productions_dict = {}
return render_template("app.html", data=data)
if __name__ == "__main__":
app.run(threaded=True)