[iterate-devel] Bug with (collect :at :beginning)

[psexton.2a at gmail.com]

When collecting values into a list, if the first value collected uses (collect val :at :beginning),
and a subsequent value does not use the ":at :beginning" clause, then an error will occur: 
"The value nil is not of type cons".

The following reproduces this error:

(iterate
 (for i from 1 to 10)
 (if (oddp i)
     (collect i :at :beginning)
     (collect i)))