Evaluates mathmatical expressions.

    Syntax: {command} <expression>

def cmd(send, msg, args):
    """Evaluates mathmatical expressions.

    Syntax: {command} <expression>

    """
    if not msg:
        send("Calculate what?")
        return
    cursor = args['db']
    scores = get_scores(cursor)
    for word in msg.split():
        if word in scores:
            msg = msg.replace(word, str(scores[word]))
    msg += '\n'
    proc = subprocess.Popen(['bc', '-l'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    try:
        output = proc.communicate(msg.encode(), timeout=5)[0].decode().splitlines()
    except subprocess.TimeoutExpired:
        proc.terminate()
        send("Execution took too long, you might have better luck with WolframAlpha.")
        return
    if len(output) > 3:
        send("Your output is too long, have you tried mental math?")
    else:
        for line in output:
            send(line)