Generate transactions from PeriodicTransaction within a DateSpan. This should be a closed span with both start and end dates specified; an open ended span will generate no transactions.

Note that new transactions require txnTieKnot post-processing. The new transactions will have three tags added: - a recur:PERIODICEXPR tag whose value is the generating periodic expression - a generated-transaction: tag - a hidden _generated-transaction: tag which does not appear in the comment.

>>> import Data.Time (fromGregorian)
>>> _ptgen "monthly from 2017/1 to 2017/4"
2017-01-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/4
    a           $1.00

2017-02-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/4
    a           $1.00

2017-03-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/4
    a           $1.00

>>> _ptgen "monthly from 2017/1 to 2017/5"
2017-01-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/5
    a           $1.00

2017-02-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/5
    a           $1.00

2017-03-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/5
    a           $1.00

2017-04-01
    ; generated-transaction: ~ monthly from 2017/1 to 2017/5
    a           $1.00

>>> _ptgen "every 2nd day of month from 2017/02 to 2017/04"
2017-02-02
    ; generated-transaction: ~ every 2nd day of month from 2017/02 to 2017/04
    a           $1.00

2017-03-02
    ; generated-transaction: ~ every 2nd day of month from 2017/02 to 2017/04
    a           $1.00

>>> _ptgen "every 30th day of month from 2017/1 to 2017/5"
2017-01-30
    ; generated-transaction: ~ every 30th day of month from 2017/1 to 2017/5
    a           $1.00

2017-02-28
    ; generated-transaction: ~ every 30th day of month from 2017/1 to 2017/5
    a           $1.00

2017-03-30
    ; generated-transaction: ~ every 30th day of month from 2017/1 to 2017/5
    a           $1.00

2017-04-30
    ; generated-transaction: ~ every 30th day of month from 2017/1 to 2017/5
    a           $1.00

>>> _ptgen "every 2nd Thursday of month from 2017/1 to 2017/4"
2017-01-12
    ; generated-transaction: ~ every 2nd Thursday of month from 2017/1 to 2017/4
    a           $1.00

2017-02-09
    ; generated-transaction: ~ every 2nd Thursday of month from 2017/1 to 2017/4
    a           $1.00

2017-03-09
    ; generated-transaction: ~ every 2nd Thursday of month from 2017/1 to 2017/4
    a           $1.00

>>> _ptgen "every nov 29th from 2017 to 2019"
2017-11-29
    ; generated-transaction: ~ every nov 29th from 2017 to 2019
    a           $1.00

2018-11-29
    ; generated-transaction: ~ every nov 29th from 2017 to 2019
    a           $1.00

>>> _ptgen "2017/1"
2017-01-01
    ; generated-transaction: ~ 2017/1
    a           $1.00

>>> let reportperiod="daily from 2018/01/03" in let (i,s) = parsePeriodExpr' nulldate reportperiod in runPeriodicTransaction True (nullperiodictransaction{ptperiodexpr=reportperiod, ptspan=s, ptinterval=i, ptpostings=["a" `post` usd 1]}) (DateSpan (Just $ Flex $ fromGregorian 2018 01 01) (Just $ Flex $ fromGregorian 2018 01 03))
[]

>>> _ptgenspan "every 3 months from 2019-05" (DateSpan (Just $ Flex $ fromGregorian 2020 01 01) (Just $ Flex $ fromGregorian 2020 02 01))

>>> _ptgenspan "every 3 months from 2019-05" (DateSpan (Just $ Flex $ fromGregorian 2020 02 01) (Just $ Flex $ fromGregorian 2020 03 01))
2020-02-01
    ; generated-transaction: ~ every 3 months from 2019-05
    a           $1.00

>>> _ptgenspan "every 3 days from 2018" (DateSpan (Just $ Flex $ fromGregorian 2018 01 01) (Just $ Flex $ fromGregorian 2018 01 05))
2018-01-01
    ; generated-transaction: ~ every 3 days from 2018
    a           $1.00

2018-01-04
    ; generated-transaction: ~ every 3 days from 2018
    a           $1.00

>>> _ptgenspan "every 3 days from 2018" (DateSpan (Just $ Flex $ fromGregorian 2018 01 02) (Just $ Flex $ fromGregorian 2018 01 05))
2018-01-04
    ; generated-transaction: ~ every 3 days from 2018
    a           $1.00

Check that this date span begins at a boundary of this interval, or return an explanatory error message including the provided period expression (from which the span and interval are derived).