42 SILICON VALLEY Piscine 2017 - evalexpr

evalexpr.py

def is_number(val):
    if val >= '0' and val <= '9':
        return True
    else:
        return False

def my_atoi(val):
    global p
    local_p = 0
    ret = 0
    
    while is_number(val[local_p]) == True:
        ret = ret * 10 + int(val[local_p])
        local_p += 1
        p += 1

    return ret

def reformat(val, ary):
    global p
    minus_flg = 0
             
    while True:
        if val[p] == '\n':
            ary.append(val[p])
            break
        
        if val[p] == ' ':
            p += 1

        if val[p] == '-':
            if is_number(val[p + 1]) == True:
                minus_flg = 1
                ary.append('(')
                ary.append(0)
                
            ary.append('-')
            p += 1
            continue
        
        if is_number(val[p]) == False:
            ary.append(val[p])
            p += 1
            continue
        else:
            ary.append(my_atoi(val[p:]))
            
            if minus_flg == 1:
                ary.append(')')
                minus_flg = 0

def factor(ary):
    global i
    print('factor', '\t', ary[i:])
    
    if ary[i] == '(':
        i += 1
        ret = expression(ary)
        i += 1
    else:
        ret = ary[i]
        i += 1

    return ret

def term(ary):
    global i
    print('term', '\t', ary[i:])
    ret = factor(ary)

    while ary[i] != '\n':
        if ary[i] == '*':
            i += 1
            ret = ret * factor(ary)
        elif ary[i] == '/':
            i += 1
            ret = int(ret / factor(ary))
        elif ary[i] == '%':
            i += 1
            ret = int(ret % factor(ary))
        else:
            break

    return ret

def expression(ary):
    global i
    print('expr', '\t', ary[i:])    
    ret = term(ary)
    
    while ary[i] != '\n':
        if ary[i] == '+':
            i += 1
            ret = ret + term(ary)
        elif ary[i] == '-':
            i += 1
            ret = ret - term(ary)
        else:
            break;

    return ret

def eval_expr(val):
    global p
    global i
    
    val = '(' + val + ')' + '\n'
    ary = []
    
    p = 0
    reformat(val, ary)
    
    i = 0
    return expression(ary)

arg = '42'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', 42)

arg = '-42'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', -42)

arg = '(-42)'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', (-42))

arg = '(1+2+3) * (-1) * 10 + 102'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', (1+2+3) * (-1) * 10 + 102)

arg = '(1+2+3) * -1 * 10 + 102'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', (1+2+3) * -1 * 10 + 102)

arg = '(-100 - -100 - -100 - -100 * 3) /10 + 2'
print('from eval', '\t', eval_expr(arg))
print('from console', '\t', (-100 - -100 - -100 - -100 * 3) /10 + 2)