The dontCollect value is used in for loops to signal that the value is not to be collected.
See For Loop for details.
dontCollect is a separate distinguished instance of the Undefined class, and so will fail in the way the undefined value does if used in computations.
Constructor
dontCollect
EXAMPLES
``` -- collect all spheres with radius less than 5 little_spheres = for i in $* collect if classOf i == sphere and i.radius < 5 then i else dontCollect
```