Editing Formula language

{{refimprove|date=August 2018}}
The '''Formula language''' is a [[scripting language]] used by [[Lotus Notes]]. It is often referred to as '''@Formula''' language (pronounced ''at-formula'') because many language elements start with the @-character. Here is an example of a selection formula:

<pre>
SELECT @NoteId = "NT0050D26"
</pre>

== Development ==
It was created by [[Ray Ozzie]] during the early development of Lotus Notes. He borrowed the compiler and decompiler from the [[Lotus 1-2-3]] spreadsheet, but unlike the spreadsheet language Formula Language was designed primarily for string and list processing, not numerical processing.  It was originally a [[Functional programming]] language with unique text list-handling features inspired by Ray Ozzie's prior use of [[Icon (programming language)|Icon]] and [[Lisp (programming language)|Lisp]].

The Formula language engine was rewritten by Damien Katz for Notes and Domino 6.<ref>{{Cite web |title= Formula Engine Rewrite |author= Damien Katz |url= http://www.damienkatz.net/2005/01/formula-engine-rewrite.html |work= Personal blog |date= January 4, 2005 |accessdate= September 30, 2016 }}</ref> New features were added to the language, such as looping and dynamic execution, and performance was improved.<ref>{{Cite web |title=Enhancements to the formula language in Domino 6  |date= November 4, 2002 |url= http://www.ibm.com/developerworks/lotus/library/ls-formula_enhancements |url-status= dead |archiveurl= https://web.archive.org/web/20121022162650/https://www.ibm.com/developerworks/lotus/library/ls-formula_enhancements/ |archivedate= October 22, 2012 |publisher= IBM |accessdate= September 30, 2016 }}</ref>

== Structure ==
The Formula language has two parts:
* ''@Functions'' for calculations and simple logic
* ''@Commands'' for performing actions in the user interface

''@Functions'' can be used in several places throughout Lotus Notes. The most important uses are:
* to select documents to show to the user in a view (a kind of index) or to select documents for further processing. In this case, the formula will evaluate to a 'true' (selected) or 'false' value (not selected) for each document.
* to provide default values for fields, to transform the data entered by the user (like stripping off redundant spaces) and to validate this data.
* to get a list of values from a Notes database or even from a relational database (using [[ODBC]]). This may be used to provide a user with a list of values to choose from.
* to process a set of documents. The formula is placed in an agent, a program or macro that can be started by a user or by the Notes server according to a schedule. When the agent is triggered, the formula executes for each selected document (this a very limited form of a loop). This is an efficient way to change many documents, if the logic is not too complicated. In case of complicated changes, [[LotusScript]] is used.

''@Commands'' are like menu commands: they perform actions in the Lotus Notes client. Examples of actions are:
* opening a Notes database
* creating an e-mail
* putting the cursor in a specific data-entry field
* closing a window
* starting an agent
@Commands are primarily used in formulas that are triggered by user action, such as in button formulas. It is possible to combine them with @Functions, for example by making execution of an @command conditional on a field value.

==References==
{{Reflist}}

[[Category:Scripting languages]]
[[Category:Functional languages]]
[[Category:Lotus Software software]]