[void] is an an object which represents "not present" or "non-existant". This is used primarily for method return values. For example, [map->find] will return [void] when the object being searched for is not contained within the map. [void] is the default return value for a method which does not explicitly return anything. It is recommended that [void] only be used in method returns and in value comparison. To illustrate, inserting a void into a map would make it difficult to determine whether or not the value exists within the map.
[void] in Lasso has the following attributes.
This example shows how void is used to indicate "not found" when searching a map.
local(mp = map('a'=1, 'b'=2, 'c'=null)) void == #mp->find('c') // yields false. 'c' was contained within the map #mp->find('d') == void // yields true. 'd' was not contained within the map