next.sa


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-- next.sa: Inherited by elements of singly linked lists.


abstract class $NEXT{T < $NEXT{T}}

abstract class $NEXT{T < $NEXT{T}} is -- The interface obeyed by classes which include NEXT{T}. next:T; -- Pointer to next element in list, if any. next(e:T); -- Set next pointer to `e'. size:INT; -- The number of elements in the list -- starting with self. Self may be void. insert(e:T); -- Insert the single element `e' after self. -- Neither may be void. append(l:T); -- Append the list `l' to the end of the -- list self. self may not be void but `l' may be. end;

class NEXT{T < $NEXT{T}} < $NEXT{T}

class NEXT{T < $NEXT{T}} < $NEXT{T} is -- Inherited by classes whose objects need to point to a list of -- objects of type T. Classes which inherit this get a `next' -- pointer and some features to manipulate it. It doesn't suport -- circular lists. attr next:T; -- Pointer to next element in list, if any. size:INT is -- The number of elements in the list starting with self. -- Self may be void. if void(self) then return 0 end; r::=1; n::=next; loop until!(void(n)); r:=r+1; n:=n.next end; return r end; insert(e:T) -- Insert the single element `e' after self. Neither may be void, -- `e.next' must be void. pre ~void(self) and ~void(e) and void(e.next) is e.next:=next; next:=e end; append(l:T) -- Append the list `l' to the end of the list self. self may -- not be void but `l' may be. pre ~void(self) is if void(next) then next:=l; return end; last::=next; loop until!(void(last.next)); last:=last.next end; last.next:=l end; end;