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 @c -*-texinfo-*-
 
-@chapter Value Expression
+@node Value Expressions, Variables, Basic Reporting Commands, Top
+@chapter Value Expressions
+
+Value expressions are an expression language used by LEDGER to
+calculate values used by the program for many different purposes:
+
+@enumerate
+@item
+The values displayed in reports
+@item
+For predicates (where truth is anything non-zero), to determine which
+postings are calculated (@option{-l}) or displayed (@option{-d}).
+@item
+For sorting criteria, to yield the sort key.
+@item
+In the matching criteria used by automated postings.
+@end enumerate
+
+Value expressions support most simple math and logic operators, in
+addition to a set of one letter functions and variables.  A function's
+argument is whatever follows it.  The following is a display predicate
+that I use with the @command{balance} command:
+
+@example
+ledger -d /^Liabilities/?T<0:UT>100 balance
+@end example
+
+The effect is that account totals are displayed only if: 1) A
+Liabilities account has a total less than zero; or 2) the absolute
+value of the account's total exceeds 100 units of whatever commodity
+contains.  If it contains multiple commodities, only one of them must
+exceed 100 units.
+
+Display predicates are also very handy with register reports, to
+constrain which transactions are printed.  For example, the following
+command shows only transactions from the beginning of the current month,
+while still calculating the running balance based on all transactions:
+
+@example
+ledger -d "d>[this month]" register checking
+@end example
+
+This advantage to this command's complexity is that it prints the
+running total in terms of all transactions in the register.  The following,
+simpler command is similar, but totals only the displayed
+postings:
+
+@example
+ledger -b "this month" register checking
+@end example
+
+@menu
+* Variables::                   
+@end menu
+
+@node Variables,  , Value Expressions, Value Expressions
+@section Variables
+
+Below are the one letter variables available in any value expression.
+For the register and print commands, these variables relate to
+individual postings, and sometimes the account affected by a
+posting.  For the balance command, these variables relate to
+accounts---often with a subtle difference in meaning.  The use of each
+variable for both is specified.
+
+@table @code
+@item t
+This maps to whatever the user specified with @option{-t}.  In a
+register report, @option{-t} changes the value column; in a balance
+report, it has no meaning by default.  If @option{-t} was not
+specified, the current report style's value expression is used.
+
+@item T
+This maps to whatever the user specified with @option{-T}.  In a
+register report, @option{-T} changes the totals column; in a balance
+report, this is the value given for each account.  If @option{-T} was
+not specified, the current report style's value expression is used.
+
+@item m
+This is always the present moment/date.
+@end table
+
+@subsection Posting/account details
+
+@table @code
+@item d
+A posting's date, as the number of seconds past the epoch.  This
+is always ``today'' for an account.
+
+@item a
+The posting's amount; the balance of an account, without
+considering children.
+
+@item b
+The cost of a posting; the cost of an account, without its
+children.
+
+@item v
+The market value of a posting, or an account without its children.
+
+@item g
+The net gain (market value minus cost basis), for a posting or an
+account without its children.  It is the same as @samp{v-b}.
+
+@item l
+The depth (``level'') of an account.  If an account has one parent,
+it's depth is one.
+
+@item n
+The index of a posting, or the count of postings affecting an
+account.
+
+@item X
+1 if a posting's transaction has been cleared, 0 otherwise.
+
+@item R
+1 if a posting is not virtual, 0 otherwise.
+
+@item Z
+1 if a posting is not automated, 0 otherwise.
+@end table
+
+@subsection Calculated totals
+
+@table @code
+@item O
+The total of all postings seen so far, or the total of an account
+and all its children.
+
+@item N
+The total count of postings affecting an account and all its
+children.
+
+@item B
+The total cost of all postings seen so far; the total cost of an
+account and all its children.
+
+@item V
+The market value of all postings seen so far, or of an account and
+all its children.
+
+@item G
+The total net gain (market value minus cost basis), for a series of
+postings, or an account and its children.  It is the same as
+@samp{V-B}.
+@end table
+
+@section Functions
+
+The available one letter functions are:
+
+@table @code
+@item -
+Negates the argument.
+
+@item U
+The absolute (unsigned) value of the argument.
+
+@item S
+Strips the commodity from the argument.
+
+@item A
+The arithmetic mean of the argument; @samp{Ax} is the same as
+@samp{x/n}.
+
+@item P
+The present market value of the argument.  The syntax @samp{P(x,d)} is
+supported, which yields the market value at time @samp{d}.  If no date
+is given, then the current moment is used.
+@end table
+
+@section Operators
+
+The binary and ternary operators, in order of precedence, are:
+
+@enumerate
+@item @samp{* /}
+@item @samp{+ -}
+@item @samp{! < > =}
+@item @samp{& | ?:}
+@end enumerate
+
+@section Complex expressions
+
+More complicated expressions are possible using:
+
+@table @code
+@item NUM
+A plain integer represents a commodity-less amount.
+
+@item @{AMOUNT@}
+An amount in braces can be any kind of amount supported by ledger,
+with or without a commodity.  Use this for decimal values.
+
+@item /REGEXP/
+@item W/REGEXP/
+A regular expression that matches against an account's full name.  If
+a posting, this will match against the account affected by the
+posting.
+
+@item //REGEXP/
+@item p/REGEXP/
+A regular expression that matches against a transaction's payee name.
+
+@item ///REGEXP/
+@item w/REGEXP/
+A regular expression that matches against an account's base name.  If
+a posting, this will match against the account affected by the
+posting.
+
+@item c/REGEXP/
+A regular expression that matches against the transaction code (the text
+that occurs between parentheses before the payee name).
+
+@item e/REGEXP/
+A regular expression that matches against a posting's note, or
+comment field.
+
+@item (EXPR)
+A sub-expression is nested in parenthesis.  This can be useful passing
+more complicated arguments to functions, or for overriding the natural
+precedence order of operators.
+
+@item [DATE]
+Useful specifying a date in plain terms.  For example, you could say
+@samp{[2004/06/01]}.
+@end table
+