lisp to join 2 line or polyline become 1 line.
When they are both LINEs, attached is my JoinLines.lsp routine with its JL command, which I've used for decades. It could presumably be modified to allow Polylines too. Bear in mind that it works by simply changing the first Line selected to the far end of the second Line selected, and deleting the second Line, and the Lines don't need to be collinear. It could be altered to check for that, if desired.
Kent Cooper, AIA 
