The type must be a symbol naming a foreign type. If the allocation is nil then the allocation type will be computed from the object argument. The slot-names are symbols or integers.
Symbols name the slots to access.
Integers are used to specify array indices. The symbol naming a slot can either be the exact symbol used when the type was defined, or it can be a keyword package symbol with the same symbol-name as the one used to define the slot. The value accessed must be a primitive value. It cannot be a structure or a whole array. The documentation is described in introduction.htm and the index is in index.htm .