"""Provide a decorator that caches expensive functions
"""
import logging
_logger = logging.getLogger(__file__)
info = _logger.info
def infop(*args):
    info(' '.join(str(a) for a in args))

def memo(f):
    #TODO: support kwargs to rval.  This requires looking up the names of f's parameters to 
    #      construct a proper key.

    #TODO: use weak references instead of a normal dict so that the cache doesn't prevent
    #      garbage collection
    cache = {}
    def rval(*args):
        if args not in cache:
            cache[args] = f(*args)
        return cache[args]
    def forget():
        for k in cache.keys():
            del cache[k]
    rval.cache = cache
    rval.forget = forget
    rval.__name__ = 'memo@%s'%f.__name__
    rval.cache = cache
    return rval