Manual:DIL Manual islight() - Seifert69/DikuMUD3 GitHub Wiki

Function:  integer islight ( u : unitptr )

  u
         Unit that you are checking
  returns
         TRUE' if item is a light, 'FALSE' if it is notway to small', 'to small', 'way to large', 'to large', or null if fits

Simply checks the item to see if it is a light.