Many views require that a history be selected (if running in a simulator) and/or a background scenario be picked in. In these cases a section of code near the top of the view - following the object declarations - is used to check that the required history and/or background is in place. If not in place the code advises the user and quits.

Common code sections are listed below.
===== Simulator - history and background required =====

<code>
boolean $answer
if $history == false
	say ("This view requires a history.")
	listen ("                              enter to continue >> ",$answer)
	quit (-1)
endif
if $background == false
	say ("This view requires a background scenario.")
	listen ("                              enter to continue >> ",$answer)
	quit (-1)
endif
</code>

FIXME - do we have a best practice on the quit() return code?

===== Simulator - both history and background optional=====

<code>
integer $index
$index = 1
if $history == true
	$index = $index + 1
endif
if $background == true
	$index = $index + 1
endif
</code>

Note the use of $index for indexing the appropriate view.

===== Simulator - history required, background optional =====
<code>
if $history == false
	say ("this view must be run with a history")
	quit (1)
endif

integer $index
if $background == false
	$index = 2
else
	$index = 3
endif
</code>

Note the use of $index for indexing the appropriate view.