Object models for computer aided design

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24 2.3.3 :􁪽􋴚􁪽􋵫ked Data Structure􁪽􋴚 􁪽􋴚􁪽􋵡averse the l􁪽􋴚􁪽􋵫ks alcng so􁪽􋵥e 􁪽􋵡ath. For exarrple, the A li􁪽􋵫ked data structure is a grou􁪽􋵯 of records 􁪽􋵴tich are tied 􁪽􋵯o;etter by var􁪽􋵯o􁪽􋵳s poi􁪽􋵴ters cr links. The 􁪽􋵮n􁪽􋵩ivi6ual reccrds are accessed by operatio􁪽􋵳s which !i􁪽􋵫ked str􁪽􋵣cture 􁪽􋵩ight be a list of a􁪽􋵰point􁪽􋵥ent dates where Each cate record conta􁪽􋵮ned a pointer to the next and a 5?ecial syrrtol rrarks the ene of the list. The operations cefi􁪽􋵥ed to traverse such a list require the introduction of a new type of variable com􁪽􋵯only called a "pointer". The poin􁪽􋵥er variables associated with linked structures are thought of as references rather than as containers and they are dyna􁪽􋵩icaly bo􁪽􋵮nc by the traversing o?erations rather :􁪽􋴳3n 􁪽􋴚􁪽􋴚􁪽􋴚􁪽􋵴 the program is corrpiled or a 􁪽􋵲rocedcre invoked. is a cirected graph where the set of records corresponds to the set of vertices, the set of pointers corresponds to the set of arcs, and the structure defines a mapping from the arcs onto the vertices. ey isposing restrictions or. the general structure, one can define trees, list, and other scecific linked structures. Khen dealing 􁪽􋵩ith linked s:ructures it is irrDorta􁪽􋵴t to realize that 􁪽􋵵uch of the in:crmation is carried in the structure itself.