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Core C++ A Software Engineering Approach phần 3

. Một nguyên tắc ghi nhớ tốt để thông qua các thông số bằng con trỏ là: Khi bạn chọn tên cho một tham số, bạn phải bắt đầu tên này với cácHình ảnh cũng cho thấy rằng khi các mã khách hàng cần các giá trị của lĩnh vực xi lanh (ví dụ, để tính toán khối lượng xi lanh, mở rộng quy mô, in ấn, hoặc thiết lập các giá trị trường), | file Administrator General 20English 20Learning it2002-7-6 core.htm include cstring using SimpcsPDFMergeand Split Unregistered Version - http www.simpopdf.com union StreetOrPOB char street 30 alternative interpretations long int POB struct Address char first 30 int kind 0 street address 1 P.O.B. StreetOrPOB second either one or another meaning char third 30 int main Address a1 a2 strcpy a1.first Doe John address with street strcpy a1.second.street 15 Oak Street a1.kind 0 strcpy a1.third Anytown MA 02445 strcpy a2.first King Amy a2.second.POB 761 a2.kind 1 address with POB strcpy a2.third Anytown MA 02445 cout a1.first endl if a1.kind 0 check data interpretation cout a1.second.street endl else cout P.O.B. a1.second.POB endl cout a1.third endl cout endl cout a2.first endl if a2.kind 0 check data interpretation cout a2.second.street endl else cout P.O.B. a2.second.POB endl cout a2.third endl return 0 This is nice but it introduces yet another level into the hierarchical structure of types. As a result the programmer has to use names like a1.second.street and this is no fun. Meanwhile the only use of type StreetOrPOB in the program is with type Address. To remedy this C supports anonymous unions. They have no name and no variable of this type can be defined however their fields can be used without any qualification. For example we can define type Address without using type StreetOrPOB but using an anonymous union instead. struct Address file Administrator General 20English 20Leaming it2002-7-6 core.htm 241 of 1187 8 17 2002 2 57 49 PM file Administrator General 20English 20Learning it2002-7-6 core.htm char first 30 int kSimpo PDF Merge and Split Unregistered Version -Ihttp www.simpopdf.com O.B. union char street 30 long int POB no second field of type StreetOrPOB char third 30 The union type is gone but type Address now has two alternative fields street and POB and they can be referred to by name as in any other field. Of course it remains the responsibility of the .