next.sa


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-- Copyright (C) 2000 by K Hopper, University of Waikato, New Zealand        --
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abstract class $NEXT{TYP < $NEXT{TYP}}

abstract class $NEXT{TYP < $NEXT{TYP}} is -- This class defines the interface to be provided by classes which -- include NEXT{TYP}. -- Version 1.1 Apr 97. Copyright K Hopper, U of Waikato -- Development History -- ------------------- -- Date Who By Detail -- ---- ------ ------ -- 1 Jun 94 bg Original -- 4 Apr 97 kh Changed for INT to CARD next : TYP ; -- element in the list, if any. next( elem : TYP ) ; -- This routine sets the next pointer to elem. size : CARD ; -- This provides the number of elements in the list starting with self. -- Self may be void. insert( elem : TYP ) ; -- This routine inserts the given element after self. Neither self -- nor elem may be void. append( list : TYP ) ; -- This routine appends the given list after self. Self may be void, -- but List may not be void. end ; -- $NEXT{T}

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

partial class NEXT{T < $NEXT{T}} < $NEXT{T} is -- This partial class implements the linked list abstraction for those -- classes whose objects need to point to a list of objects of type T. -- Classes which inherit this get a `next' component and some features to -- manipulate it. It does not suport circular lists. -- Version 1.2 Nov 98. Copyright K Hopper, U of Waikato -- Development History -- ------------------- -- Date Who By Detail -- ---- ------ ------ -- 1 Jun 96 bg Original -- 4 Apr 97 kh Changed for INT to CARD -- 6 Nov 98 kh Refined, added pre/post conditions. attr next : T ; -- next element in list, if any. size : CARD pre true post (void(self) and (result = 0)) or (~void(self) and (result > 0)) is -- This routine returns the number of elements in the list starting -- with self. if void(self) then return 0 end ; res : CARD := 1 ; loc_next : T := next ; loop -- scan all the list until!(void(loc_next)) ; res := res + 1 ; loc_next := loc_next.next end ; return res end ; insert( elem : T ) pre ~void(self) and ~void(elem) and void(elem.next) post (size = (initial(size) + 1)) is -- This routine inserts the single element given after self. elem.next := next ; next := elem end ; append( list : T ) pre ~void(self) post (size = (initial(size) + list.size)) is -- This routine appends the given list at the end of self. Self may not -- be void but the list may be. if void(next) then next := list ; return end ; last : T := next ; loop -- need to scan to end first! until!(void(last.next)) ; last := last.next end ; last.next := list end ; end ; -- NEXT{T}