@c  -l, --limit EXPR       calculate only postings matching EXPR

Value expressions can be quite complex, and are treated more fully in
@ref{Value expressions}.  They can be used for limiting a report with
@option{--limit} (@option{-l}).  The following command report income
since august, but expenses since october:

@example
ledger -l '(/income/&d>=[aug])|(/expenses/&d>=[oct])' reg
@end example

The basic form of this value expression is @samp{(A&B)|(A&B)}.  The
@samp{A} in each part matches against an account name with
@samp{/name/}, while each @samp{B} part compares the date of the
posting (@samp{d}) with a specified month.  The resulting report
will contain only postings which match the value expression.

@c  -t, --amount EXPR      use EXPR to calculate the displayed amount
@c  -T, --total EXPR       use EXPR to calculate the displayed total

Another use of value expressions is to calculate the amount reported
for each line of a register report, or for computing the subtotal of
each account shown in a balance report.  This example divides each
posting amount by two:

@example
ledger -t 'a/2' reg ^exp
@end example

The @option{-t} option doesn't affect the running total, only how the
posting amount is displayed.  To change the running total, use
@option{-T}.  In that case, you will likely want to use the total
(@samp{O}) instead of the amount (@samp{a}):

@example
ledger -T 'O/2' reg ^exp
@end example