Help with Python: Implementing Algorithm

[FallArk]

Working solution:

def eval_infix_sum(expr,pos):
    ans, pos = eval_infix_product(expr,pos)
    while expr[pos] == '+' or expr[pos] == '-':
        if expr[pos] == '+':
            rhs,pos = eval_infix_product(expr,pos + 1)
            ans = ans + rhs
        elif expr[pos] == '-':
            rhs,pos = eval_infix_product(expr,pos + 1)
            ans = ans - rhs
    return ans,pos
def eval_infix_product(expr,pos):
    ans,pos = eval_infix_factor(expr,pos)
    while expr[pos] == '*' or expr[pos] == '/' or expr[pos] == '%':
        if expr[pos] == '*':
            rhs,pos = eval_infix_factor(expr,pos + 1)
            ans = ans * rhs
        elif expr[pos] == '/':
            rhs,pos = eval_infix_factor(expr,pos + 1)
            ans = ans / rhs
        elif expr[pos] == '%':
            rhs,pos = eval_infix_factor(expr,pos + 1)
            ans = ans % rhs
    return ans,pos
def eval_infix_factor(expr,pos):
    if expr[pos] == '(':
        ans,pos = eval_infix_sum(expr,pos+1)
        return ans,pos+1
    else:
        return int(expr[pos]),pos+1
def eval_infix_list(expr):
    ans,discard = eval_infix_sum(expr,0)
    return ans
def eval_infix(expr):
    return eval_infix_list(expr.split() + [ ";"])

Working on making it support minus(es?):p

 

[I like Serena]

Looks good! (Yes)