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 Bronze Challenge (1) CLI Calculator filter_list Linear Mode Threaded Mode View a Printable Version Author Message
Challenge (1) CLI Calculator #1
In this Python challenge, you will attempt to a make a CLI (Command Line Interface) calculator. Basically, what that means is: a calculator that can interpret simple math equations (e.g. 2+3-5*6 => -25). It must correctly compute addition, subtraction, multiplication, and division. It sounds simple, but it can get a little complicated at times. You cannot use eval() or anything like that, you MUST parse everything yourself.
I am really interested in what you come up with. Good luck! 151st post! RE: Challenge (1) CLI Calculator #2
Done!
Code:
import re

def isMore(tokens):
for t in tokens:
if t == "*" or t == "/":
return True

return False

def lex(equation):
# remove all the whitespaces from the equation string
equation = equation.replace(" ", "")
return re.findall("[0-9]+|[\+, \-, \*, \/]", equation)

def evaluate1(tokens, isOrigin = False):
for i in range(0, len(tokens)):
if tokens[i] == "*":
a = int(tokens[i - 1]) * int(tokens[i + 1])
tokens = tokens[:i - 1]
tokens.insert(i, a)
break

elif tokens[i] == "/":
a = int(tokens[i - 1]) / int(tokens[i + 1])
tokens = tokens[:i - 1]
tokens.insert(i, a)
break

if isMore(tokens):
tokens = evaluate1(tokens)

def evaluate2(tokens, isOrigin = False):
if tokens == "+":
a = int(tokens) + int(tokens)
tokens = tokens[3:]
tokens.insert(0, a)

elif tokens == "-":
a = int(tokens) - int(tokens)
tokens = tokens[3:]
tokens.insert(0, a)

if len(tokens) > 1:
tokens = evaluate2(tokens)

if isOrigin:

else:

equation = raw_input("Enter an equation: ")
tokens = lex(equation)
tokens = evaluate1(tokens, isOrigin = True)
print(evaluate2(tokens, isOrigin = True))

And no, I didn't search up anything about this type of calculator for help.

RE: Challenge (1) CLI Calculator #3
Well, since my last code was just a lame hack... I re-wrote it to make it much neater and more professional.
No recursion this time... too clunky.
Code:
import re

def lex(equation):
# remove all the whitespaces from the equation string
equation = equation.replace(" ", "")
return re.findall("[0-9]+|[\+, \-, \*, \/]", equation)

def evalMulDiv(tokens):
i = 0
while i < len(tokens):
if tokens[i] == "*":
tokens = tokens[:i - 1] + [int(tokens[i - 1]) * int(tokens[i + 1])] + tokens[i + 2:]
i -= 2

elif tokens[i] == "/":
tokens = tokens[:i - 1] + [int(tokens[i - 1]) / int(tokens[i + 1])] + tokens[i + 2:]
i -= 2

i += 1

i = 0
while i < len(tokens):
if tokens[i] == "+":
tokens = tokens[:i - 1] + [int(tokens[i - 1]) + int(tokens[i + 1])] + tokens[i + 2:]
i -= 2

elif tokens[i] == "-":
tokens = tokens[:i - 1] + [int(tokens[i - 1]) - int(tokens[i + 1])] + tokens[i + 2:]
i -= 2

i += 1

def calc(equation):
tokens = lex(equation)
tokens = evalMulDiv(tokens)

equation = raw_input("> ")
print(calc(equation))

@Megan! You try! I think I will make a guide on CLI calculators soon. (possibly non-language specific -- pseudocode)

RE: Challenge (1) CLI Calculator #4
I'm new to Python and don't really know how your script works. Mine sucks but I did my best. Don't know if this is what you were looking for or not.

Code:
def a(n1,n2):
return float(n1 + n2)
def s(n1,n2):
return float(n1 - n2)
def m(n1,n2):
return float(n1 * n2)
def d(n1,n2):
return float(n1 / n2)
c = raw_input("Operation? (add, sub, mult, div): ")
n1 = float(raw_input("Enter the first number: "))
n2 = float(raw_input("Enter the second number: "))

if c == "add":
print(a(n1,n2))
elif c == "sub":
print(s(n1,n2))
elif c == "mult":
print(m(n1,n2))
elif c == "div":
print(d(n1,n2))
else:
print("The operation you entered does not exist.")

RE: Challenge (1) CLI Calculator #5
(12-15-2015, 04:22 AM)meow Wrote: I'm new to Python and don't really know how your script works. Mine sucks but I did my best. Don't know if this is what you were looking for or not.

Code:
def a(n1,n2):
return float(n1 + n2)
def s(n1,n2):
return float(n1 - n2)
def m(n1,n2):
return float(n1 * n2)
def d(n1,n2):
return float(n1 / n2)
c = raw_input("Operation? (add, sub, mult, div): ")
n1 = float(raw_input("Enter the first number: "))
n2 = float(raw_input("Enter the second number: "))

if c == "add":
print(a(n1,n2))
elif c == "sub":
print(s(n1,n2))
elif c == "mult":
print(m(n1,n2))
elif c == "div":
print(d(n1,n2))
else:
print("The operation you entered does not exist.")

Well, that's not exactly what I was looking for. But it is okay; your did your best! Cool on you for learning Python though. Basically, what I meant by a CLI calculator is that it takes a string such as "2 +8/2 * 4" and outputs the correct number (18). (note the use of operator precedence -- I do not require parentheses though)
Thanks for trying!!! NOTE: Windows calc.exe doesn't even use operator precedence!?!?!

RE: Challenge (1) CLI Calculator #6
If you could explain your code that'd be cool, especially the eval functions.

Why tokens?

RE: Challenge (1) CLI Calculator #7
(12-15-2015, 08:55 AM)God Wrote: If you could explain your code that'd be cool, especially the eval functions.

Why tokens?

Ok, I will make a separate guide on this.
Be looking for it. I've finished!
Enjoy! (This post was last modified: 12-15-2015, 03:20 PM by m0dem.)

RE: Challenge (1) CLI Calculator #8
J:
Code:
".;2}input

Python (supports addition, subtraction, multiplication, division, exponents, and modulus):
Code:
import re
import operator as op

ops={'+': op.add,'-': op.sub,'*': op.mul,'/': op.div,'^': op.pow,'%': op.mod}

while 1:
e=raw_input('} ')
for i in re.finditer('[\+,\-,\*,\/,\^,\%]',e): print ops[i.group()](int(e[:i.start()]),int(e[i.start()+1:]))

RE: Challenge (1) CLI Calculator #9
(12-16-2015, 03:30 PM)Nevermore Wrote: J:
Code:
".;2}input

Python (supports addition, subtraction, multiplication, division, exponents, and modulus):
Code:
import re
import operator as op

ops={'+': op.add,'-': op.sub,'*': op.mul,'/': op.div,'^': op.pow,'%': op.mod}

while 1:
e=raw_input('} ')
for i in re.finditer('[\+,\-,\*,\/,\^,\%]',e): print ops[i.group()](int(e[:i.start()]),int(e[i.start()+1:]))
Cool! Really compact code.
But.. your code can only do one operation per input. (you can't do "5+5*5" or "4*3-2*3")
You should be able to do an equation of arbitrary length.

RE: Challenge (1) CLI Calculator #10
(12-16-2015, 03:51 PM)m0dem Wrote: Cool! Really compact code.
But.. your code can only do one operation per input. (you can't do "5+5*5" or "4*3-2*3")
You should be able to do an equation of arbitrary length.

I just got bored in history, I'll take it seriously and finish it later.

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