def pre2post(expr):
expr = expr.split(" ")
new_segement = ""
while len(expr) != 1:
for counter, char in enumerate(expr):
if not counter < len(expr) - 2:
break
if char in operators.keys():
try:
if not expr[counter + 1] in operators.keys():
if not expr[counter + 2] in operators.keys():
new_segement = expr[counter + 1] + " "
new_segement = new_segement + expr[counter +
2] + " " + char
for x in range(3):
expr.pop(counter)
except:
print(
"\n\n\tInvalid Prefix Expression, Try again with new Input"
)
return [False, []]
else:
if new_segement:
if counter != 0:
expr = expr[:counter] + [new_segement
] + expr[counter:]
else:
expr = [new_segement] + expr
new_segement = ""
return [True, expr[0]]
def check_format(expr):
global operators, expression_format
if expr[0] in operators.keys():
exp_format = expression_format[0]
elif expr[-1] in operators.keys():
exp_format = expression_format[2]
else:
exp_format = expression_format[1]
print("\n\tExpression Format is ---> {}".format(exp_format))
return exp_format
def check_space(expr):
expr_list = expr.split(" ")
no_operators = True
no_alnum = True
for x in expr_list:
if x in operators.keys():
no_operators = False
if x.isalnum():
no_alnum = False
if no_operators or no_alnum:
return False
if not all(char for char in expr_list):
return False
for c, x in enumerate(expr):
if x == expr[-1]:
continue
if x.isspace() or expr[c + 1].isspace():
continue
else:
if x.isdigit() and expr[c + 1].isdigit():
continue
else:
return False
return True
def post2in(expr):
operand_list = []
expr = expr.split(" ")
for char in expr:
if char.isalnum():
operand_list.append(char)
if char in operators.keys():
try:
temp = "( " + operand_list[
-2] + " " + char + " " + operand_list[-1] + " )"
except:
print("\n\n\tOperand List empty, incorrect input")
return [False, []]
else:
operand_list = operand_list[:-2]
operand_list.append(temp)
try:
infix_expr = operand_list[0][1:-1].strip()
except:
print("\n\n\tInfix Can't be proccessed incorrect input")
return [False, []]
else:
pass
return [True, infix_expr]
def in2pre(expr):
prefix = []
opstack = []
expr = expr[::-1]
expr = expr.split(" ")
for counter, char in enumerate(expr):
if char == "(":
expr[counter] = ")"
elif char == ")":
expr[counter] = "("
else:
pass
if char.isalnum():
prefix.append(char)
elif char in operators.keys():
if not opstack:
opstack.append(char)
else:
while opstack:
last_item = opstack[-1]
if last_item == ")":
opstack.append(char)
break
elif operators[char] > operators[last_item]:
opstack.append(char)
break
elif operators[char] == operators[last_item]:
if not char == "*":
opstack.append(char)
break
else:
prefix.append(opstack.pop(-1))
opstack.append(char)
break
else:
prefix.append(opstack.pop(-1))
opstack.append(char)
break
else:
if char == ")":
opstack.append(char)
elif char == "(":
while opstack[-1] != ")":
prefix.append(opstack.pop(-1))
opstack.pop(-1)
else:
pass
while opstack:
prefix.append(opstack.pop(-1))
prefix = " ".join(prefix[::-1])
return [True, prefix]