rebol/rebol — pull request #205 by BrianHawley (2014-03-06 04:28:57+00:00)
Title: TO-VALUE function

This fills a hole in the basic evaluation model: converting non-values to values. This is how you turn an unset value that doesn't have to be considered erroneous into a nice safe none; all else passed through. Filters out the unset values from the data flow.

See http://issue.cc/r3/2003 for details.