types.py 文件源码

def parse_unit(item):
    if isinstance(item, ast.Name):
        if item.id not in valid_units:
            raise InvalidTypeException("Invalid base unit", item)
        return {item.id: 1}
    elif isinstance(item, ast.Num) and item.n == 1:
        return {}
    elif not isinstance(item, ast.BinOp):
        raise InvalidTypeException("Invalid unit expression", item)
    elif isinstance(item.op, ast.Mult):
        left, right = parse_unit(item.left), parse_unit(item.right)
        return combine_units(left, right)
    elif isinstance(item.op, ast.Div):
        left, right = parse_unit(item.left), parse_unit(item.right)
        return combine_units(left, right, div=True)
    elif isinstance(item.op, ast.Pow):
        if not isinstance(item.left, ast.Name):
            raise InvalidTypeException("Can only raise a base type to an exponent", item)
        if not isinstance(item.right, ast.Num) or not isinstance(item.right.n, int) or item.right.n <= 0:
            raise InvalidTypeException("Exponent must be positive integer", item)
        return {item.left.id: item.right.n}
    else:
        raise InvalidTypeException("Invalid unit expression", item)


# Parses an expression representing a type. Annotation refers to whether
# the type is to be located in memory or storage