Thus, an expression can know if the context in which it's being
evaluated requires a string, and if so, determine it's output
accordingly. For example:
account ; returns the full name of the posting's account
account.total ; here the context is SCOPE, so account is an obj
These can occur in many places:
; Within an automated transaction, the assert is evaluated every time
; a posting is matched, with the expression context set to the
; matching posting.
= /Food/
assert account("Expenses:Food").total >= $100
2010-06-12 Sample
Expenses:Food $100
Assets:Checking
; At file scope, the expression is evaluated with "global" scope.
assert account("Expenses:Food").total == $100
; At the top of a transction, the assertion's scope is the
; transaction. After a posting, the scope is that posting. Note
; however that account totals are only adjusted after successful
; parsing of a transaction, which means that all the assertions below
; are true, even though it appears as though the middle posting should
; affect the total immediately (which is not the case).
2010-06-12 Sample 2
assert account("Expenses:Food").total == $100
Expenses:Food $50
assert account("Expenses:Food").total == $100
Assets:Checking
assert account("Expenses:Food").total == $100
For example, consider the following automated transaction:
= /Food/
; Next Date:: date + 10
(Expenses:Tax) 1.00
; Next Date:: date + 20
This will add a metadata field named 'Next Date' to the _matching
posting_, with a value that is 10 days later than that posting. It will
also generate a new posting for that transaction, whose amount is the
same as the matching posting. Further, it will add a 'Next Date'
metadata tag to the _generated posting_ whose value is 20 days later
than the date of the matching posting.
For example, just the word "account" returns the name of the current
posting's account, but account("Expenses:Food") returns the actual
account object, so that it's total may be accessed.
The metadata construct 'Key: Value' is now just a special case for
'Key:: "Value"'. Another after a :: in metadata setting is parsed as a
full value expression and typed as such. For example:
; Key:: $400 + $500
ledger -l 'tag("Key") < $1000'
This is to work around undefined behavior according to the Standard,
[lib.res.on.functions]/2:
"In particular, the effects are undefined in the following cases: [..]
- if an incomplete type (3.9) is used as a template argument when
instantiating a template component."
