def half_int_float_to_str(f):
    """Given the decimal representation of a half-integer or integer, returns
    the string fraction representation.
    Example:
    > half_int_float_to_str(1.5)
    '3/2'
    """
    if int(f) - f == 0:
        return str(int(f))
    else:
        return str(int(2 * f)) + '/2'