subtract_and_divide_reduce.rs

fn reduce_subtraction(stack: &mut Vec<Token>) -> Result<Token, RuntimeError> {
    let operands = unwrap_operand_tokens(stack);
    match operands {
        Ok(mut operand_vec) =>{
            let initial_positive_option = operand_vec.pop();
            if let Some(initial_positive) = initial_positive_option {
                Ok(Token::Operand(
                    operand_vec
                        .iter()
                        .fold(initial_positive, |sum, value| sum - value)))
            } else {
                Err(RuntimeError{})
            }
        },
        Err(_) => Err(RuntimeError{})
    }
}

fn reduce_division(stack: &mut Vec<Token>) -> Result<Token, RuntimeError> {
    let operands = unwrap_operand_tokens(stack);
    match operands {
        Ok(mut operand_vec) =>{
            let initial_numerator_option = operand_vec.pop();
            if let Some(initial_numerator) = initial_numerator_option {
                Ok(Token::Operand(
                    operand_vec
                        .iter()
                        .fold(initial_numerator, |numerator, value| numerator / value)))
            } else {
                Err(RuntimeError{})
            }
        },
        Err(_) => Err(RuntimeError{})
    }
}