b) or there must be a way of storing the type information in other BATs
Did I already apologise for my dumb questions? :-) I found bbp.getNames, getHeadType, getTailType and I think I see how I could extract the necessary information with them. However, the question remains as how to create a bat with specific head and tail types which are given as String type names (result of getHeadType and getTailType). In bat5.mal the following functions which would have solved this problem are commented out: #command bat(ht:int, tt:int) :bat[:any_1,:any_2] #address BKCnewBat #comment "Creates a new empty transient BAT with head- and tail-types # as indicated."; # #command bat(ht:int, tt:int, size:int) :bat[:any_1,:any_2] #address BKCnewBATint #comment "Creates a new empty BAT, allocating 'size' elements."; # #command bat(ht:int, tt:int, size:lng) :bat[:any_1,:any_2] #address BKCnewBATlng #comment "Creates a new empty BAT, allocating 'size' elements."; I think I'll try to understand the output of some simple 'explain SELECT' statements. Good night Kambiz