申論題

這是一個簡單的解析器，它會根據由左至右的規則計算四則運算的結果，當進行除法時，它會捨去任何小數位數來只取整數結果。以下是該解析器的 Python 實現：

python
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def simple_calculator(expression):
    # Initial total is the first number in the expression
    elements = expression.split()
    total = int(elements[0])
    
    # Process the rest of the expression
    i = 1
    while i < len(elements):
        operator = elements[i]
        number = int(elements[i + 1])

        if operator == '+':
            total += number
        elif operator == '-':
            total -= number
        elif operator == '*':
            total *= number
        elif operator == '/':
            total //= number  # Use floor division to get an integer result
        
        i += 2  # Move past the operator and number

    return total

# Example usage:
# expression = input("Enter an expression: ")
# result = simple_calculator(expression)
# print("The result is:", result)

# Since we cannot get user input in this environment, let's use the given example
example_expression = "121 * 3 / 2"
result = simple_calculator(example_expression.replace('*', ' * ').replace('/', ' / '))
print("The result is:", result)