Mark Harrah c669606999 TaskKey[T].previous: Option[T], which returns the value of the task the last time it executed. ... This requires a Format[T] to be implicitly available at the call site and requires the task to be referenced statically (not in a settingDyn call). References to previous task values in the form of a ScopedKey[Task[T]] + Format[T] are collected at setting load time in the 'references' setting. These are used to know which tasks should be persisted (the ScopedKey) and how to persist them (the Format). When checking/delegating previous references, rules are slightly different. A normal reference from a task t in scope s cannot refer to t in s unless there is an earlier definition of t in s. However, a previous reference does not have this restriction. This commit modifies validateReferenced to allow this. TODO: user documentation TODO: stable selection of the Format when there are multiple .previous calls on the same task TODO: make it usable in InputTasks, specifically Parsers		2013-12-06 20:45:01 -05:00
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src	TaskKey[T].previous: Option[T], which returns the value of the task the last time it executed.	2013-12-06 20:45:01 -05:00
NOTICE	higher-kinded heterogeneous lists: MList[M[_]]	2010-05-30 18:42:58 -04:00