Chapter $6-$Programming Project: using a stack, implement a function that takes in an arithmetic expression, and evaluates it$,$ supported operations are $+$ and $-,$ which have same precedence. This is a simplified version of the eval$\_$expr function we built in lecture.

Use the base code provided:

from stack$\_$list import Stack, Empty

# Assignment: Programming Project

def eval$\_$expr$($expression$)$:

$"""$

This function evaluates an arithmetic expression using a stack. The expression can contain digits and the operators $\text{'}+\text{'}$ and $\text{'}-\text{'}.$

The $\text{'}+\text{'}$ and $\text{'}-\text{'}$ operators have the same precedence and the expression is evaluated from left to right.

Parameters:

expression $($str$)$: The arithmetic expression to evaluate. The expression can contain digits $(0-9)$ and the operators $\text{'}+\text{'}$ and $\text{'}-\text{'}.$

Returns:

int: The result of the arithmetic expression.

$"""$

# WRITE YOUR CODE HERE

# Step $1$: Initialize stacks for numbers and operators.

# Hint: Use Stack class to create two stacks, one for numbers and one for operators.

# Step $2$: Parse the expression.

# Hint: Loop through each character in the expression.

# If the character is a digit, accumulate it in a string for multi$-$digit numbers.

# If the character is an operator, push the accumulated number to the number stack, and push the operator to the operator stack.

# Step $3$: Push the last accumulated number onto the number stack.

# Hint: After the loop, there might be a number that you haven't pushed onto the number stack yet.

# Step $4$: Reverse the stacks

# Hint: Create two new temporary stacks and pop from the original stacks to push into these, thereby reversing the order.

# Step $5$: Initialize the result with the first number from the reversed number stack.

# Hint: Pop the first number off the reversed number stack and store it as your initial result.

# Step $6$: Perform the operations.

# Hint: Loop through the reversed operator stack, pop one operator and one number each time from their respective reversed stacks,

# and update the result accordingly.

# Step $7$: Return the final result.

# Hint: The final result is the value you get after applying all operators to the numbers.

return $0$ # replace this line with the correct return

if $\_\_$name$\_\_==\text{'}\_\_$main$\_\_\text{'}$:

expression $="1+2"$

print$($eval$\_$expr$($expression$))$ # $3$

expression $="1+2-3"$

print$($eval$\_$expr$($expression$))$ # $0$

expression $="1+2-3+4-5"$

print$($eval$\_$expr$($expression$))$ # $-1$