def __add__(self, period_tensor):
"""Adds a tensor of periods.
When adding months or years, the resulting day of the month is decreased
to the largest valid value if necessary. E.g. 31.03.2020 + 1 month =
30.04.2020, 29.02.2020 + 1 year = 28.02.2021.
Args:
period_tensor: A `PeriodTensor` object broadcastable to the shape of
"self".
Returns:
The new instance of DateTensor.
#### Example
```python
dates = tff.datetime.dates_from_tuples([(2020, 2, 25), (2020, 3, 31)])
new_dates = dates + tff.datetime.month()
# DateTensor([(2020, 3, 25), (2020, 4, 30)])
new_dates = dates + tff.datetime.month([1, 2])
# DateTensor([(2020, 3, 25), (2020, 5, 31)])
```
"""
period_type = period_tensor.period_type()
if period_type == constants.PeriodType.DAY:
ordinals = self._ordinals + period_tensor.quantity()
return from_ordinals(ordinals)
if period_type == constants.PeriodType.WEEK:
return self + periods.PeriodTensor(period_tensor.quantity() * 7,
constants.PeriodType.DAY)
def adjust_day(year, month, day):
return tf.math.minimum(day, _num_days_in_month(month, year))
if period_type == constants.PeriodType.MONTH:
m = self._months - 1 + period_tensor.quantity()
y = self._years + m // 12
m = m % 12 + 1
d = adjust_day(y, m, self._days)
return from_year_month_day(y, m, d, validate=False)
if period_type == constants.PeriodType.YEAR:
y = self._years + period_tensor.quantity()
# Use tf.shape to handle the case of dynamically shaped `y`
m = tf.broadcast_to(self._months, tf.shape(y))
d = adjust_day(y, m, self._days)
return from_year_month_day(y, m, d, validate=False)
raise ValueError("Unrecognized period type: {}".format(period_type))
def __sub__(self, period_tensor):
"""Subtracts a tensor of periods.
When subtracting months or years, the resulting day of the month is
decreased to the largest valid value if necessary. E.g. 31.03.2020 - 1 month
= 29.02.2020, 29.02.2020 - 1 year = 28.02.2019.
Args:
period_tensor: a PeriodTensor object broadcastable to the shape of "self".
Returns:
The new instance of DateTensor.
"""
return self + periods.PeriodTensor(-period_tensor.quantity(),
period_tensor.period_type())
def subtract_period_and_roll(
self,
date_tensor,
period_tensor,
roll_convention=constants.BusinessDayConvention.NONE):
"""Subtracts given periods from given dates and rolls to business days.
The original dates are not rolled prior to subtraction.
Args:
date_tensor: DateTensor of dates to subtract from.
period_tensor: PeriodTensor broadcastable to `date_tensor`.
roll_convention: BusinessDayConvention. Determines how to roll a date that
falls on a holiday.
Returns:
The resulting DateTensor.
"""
minus_period_tensor = periods.PeriodTensor(-period_tensor.quantity(),
period_tensor.period_type())
return self.add_period_and_roll(date_tensor, minus_period_tensor,
roll_convention)
