def upcast_char(*args):
t = _upcast_memo.get(args)<EOL>if t is not None:<EOL><INDENT>return t<EOL><DEDENT>t = upcast(*map(np.dtype, args))<EOL>_upcast_memo[args] = t<EOL>return t<EOL>
Same as `upcast` but taking dtype.char as input (faster).