Hello, please help me understand how to solve

Question

Write a calculator to perform basic arithmetic, but using an alternative syntax for writing the expressions.
In this alternative notation, the operators precede the operands. For example while in traditional notation we might write 3+ 4, Instead we would write + 3 4.
The main advantage of this format is that it does not require parentheses for any ambiguous expression.
Traditional notation
3+4
3-(4*5)
(3+4)*5
(3-4)/(5+2)
Alternative notation
+ 3 4
- 3 * 4 5
* + 3 4 5
/ - 3 4 + 5 2
In the code provided, exports a calculate function. This function is expected to take an alternative expression as a string, and output the numerical solution.

Please Implement the calculate function to solve expressions in the alternative format as expected.

Answer 1

Looks like Bob_Li has figured it out.

But I've found a github project about this.

https://github.com/aghamohammadi/prefix-calculator

You can find an alternative solution here.
https://github.com/aghamohammadi/prefix-calculator/blob/main/app/calculator.js

It works in sololearn playground if you remove exports. from the calculate function.

Answer 2

Don't post the code like that, please see the post

https://sololearn.com/compiler-playground/Wek0V1MyIR2r/?ref=app

Answer 3

Here is my code:
exports.calculate = function(expression){
const token = [];
const stack = [];
for (let i=tokens.length-1; i>=0; i++){
if(isNaN(tokens[i])){
let result;
switch(tokens[i]){
case '+':
result=stack.pop()+stack.pop()
break;
case '-':
result=stack.pop()+stack.pop()
break;
case '*':
result=stack.pop()+stack.pop()
break;
case '/':
result=stack.pop()+stack.pop()
break;
}
stack.push(result);
} else {
stack.push(tokens[i]);
}
}
return stack.pop[i];
}

Answer 4

Lilit
remember to convert your string to number.

maybe something like this:

https://sololearn.com/compiler-playground/WRxEnDe6q7yR/?ref=app

Answer 5

Can you share your attempt?

Answer 6

This method of expression is called Polish Notation. For better understanding of the assignment, see this link: https://en.m.wikipedia.org/wiki/Polish_notation

Answer 7

Python
def calculate(expression):
"""
This function evaluates an expression written in Reverse Polish Notation (RPN).

Args:
expression: A string containing the expression in RPN format.

Returns:
The numerical result of the expression.
"""
stack = []
for token in expression.split():
if token.isdigit():
stack.append(float(token)) # Handle decimals as well
else:
try:
num2 = stack.pop()
num1 = stack.pop()
result = {
'+': num1 + num2,
'-': num1 - num2,
'*': num1 * num2,
'/': num1 / num2
}[token]
stack.append(result)
except IndexError:
raise ValueError("Invalid expression: missing operands")
if len(stack) != 1:
raise ValueError("Invalid expression: extra operands")
return stack.pop()

Answer 8

Chris Coder
thanks. great link. I can see a few places where my code could be improved. Those links are really helpful.

Answer 9

I don’t know anything that they didn’t explain.

Answer 10

Yes, I see but my code doesn't work

Answer 11

I can’t see your code.

Answer 12

Please I need to learn

Answer 13

Hello guys