Bracket Parser

Bracket Parser.py

# expression := term operator term
# term := literal
# term := "(" expression ")"

# 0 - bracket open
# 1 - bracket close
# 2 - number
# 3 - operator

tokens = [
    {"type": 0},
    {"type": 2, "value": 10 ** 1},
    {"type": 3},
    {"type": 2, "value": 10 ** 2},
    {"type": 1},
    {"type": 3},
    {"type": 0},
    {"type": 0},
    {"type": 2, "value": 10 ** 4},
    {"type": 3},
    {"type": 2, "value": 10 ** 5},
    {"type": 1},
    {"type": 3},
    {"type": 2, "value": 10 ** 7},
    {"type": 1}
]

def cons(tokens):
    pos = 0
    start = pos
    term1 = None
    if tokens[pos]["type"] == 0:
        count = 1
        while count > 0:
            pos += 1
            if tokens[pos]["type"] == 0:
                count += 1
            elif tokens[pos]["type"] == 1:
                count -= 1
        term1 = cons(tokens[(start + 1):pos])
    elif tokens[pos]["type"] == 2:
        term1 = tokens[pos]["value"]
    else:
        print("syntax error")
        return

    pos += 1
    if tokens[pos]["type"] != 3:
        print("syntax error")
        return

    pos += 1
    start = pos
    term2 = None
    if tokens[pos]["type"] == 0:
        count = 1
        while count > 0:
            pos += 1
            if tokens[pos]["type"] == 0:
                count += 1
            elif tokens[pos]["type"] == 1:
                count -= 1
        term2 = cons(tokens[(start + 1):pos])
    elif tokens[pos]["type"] == 2:
        term2 = tokens[pos]["value"]
    else:
        print("syntax error")
        return

    return term1 + term2