"""BulletML expression evaluator. http://www.asahi-net.or.jp/~cs8k-cyu/bulletml/index_e.html """ # BulletML assumes 1/2 = 0.5. from __future__ import division import random import re from bulletml.errors import Error class ExprError(Error): """Raised when an invalid expression is evaluated/compiled.""" pass class NumberDef(object): """BulletML numeric expression. This translates BulletML numeric expressions into Python expressions. The Examples: 35 360/16 0.7 + 0.9*$rand 180-$rank*20 (2+$1)*0.3 """ def __init__(self, expr): try: expr = expr.__original except AttributeError: pass self.__original = expr repl = lambda match: "params[%d]" % (int(match.group()[1:]) - 1) expr = re.sub(r"\$\d+", repl, expr.lower()) self.__expr = expr.replace("$rand", "rand").replace("$rank", "rank") try: try: self.__value = eval(self.__expr, dict(__builtins__={})) except NameError: fake = [0] * 99 variables = dict(rand=1, rank=1, params=fake, __builtins__={}) value = eval(self.__expr, variables) if not isinstance(value, (int, float)): raise TypeError(expr) self.__value = None except Exception: raise ExprError(expr) self.__expr = compile(self.__expr, __file__, "eval") def __call__(self, params, rank): """Evaluate the expression and return its value.""" if self.__value is not None: return self.__value rand = random.random() variables = dict(rand=rand, rank=rank, params=params) return eval(self.__expr, variables) def __repr__(self): return "%s(%r)" % (type(self).__name__, self.__original) class INumberDef(NumberDef): """A NumberDef, but returns rounded integer results.""" def __call__(self, params, rank): return int(round(super(INumberDef, self).__call__(params, rank)))