A union in C is a user-defined data type that allows you to store different data types in the same memory location. This can be useful for saving memory, especially when you only need to store one value at a time.
union Message { int int_value; float float_value; char *str_value; // 此处用个指针代替,这样可以存储更多数据到堆中 }; // 定义一个承载Message的类型,可以区分不同的枚举数据 struct DataMessage { DataType type; // 这个data的数据类型 union Message msg; // 具备多种类型存储的能力 }; // ...
7operatorlong()const{returndata.l;} 8private: 9enumtype {Int, String }; 10union 11{ 12constchar*ch; 13inti; 14} datatype; 15type stype; 16test(test&); 17test&operator=(consttest&); 18}; 19test::test(constchar*p):stype(String),datatype.ch(p) { } 20test::test(intin):styp...
operator long() const {return data.l;} private: enum type {Int, String }; union { const char* ch; int i; }datatype; type stype; test(test&); test& operator=(const test&); }; test::test(const char *p):stype (String),datatype.ch(p) { } test::test(int in):stype(Int),...
例4: #include<stdio.h> voidmain() { unionnumber {/*定义一个联合*/ inti; struct {/*在联合中定义一个结构*/ charfirst; charsecond; }half; }num; num.i=0x4241;/*联合成员赋值*/ printf("%c%c/n",num.half.first,num.half.second); num.half.first='a';/*联合中结构成员赋值*/ num....
In C++, the union keyword is not required.העתק union DATATYPE var2; // C declaration of a union variable DATATYPE var3; // C++ declaration of a union variable A variable of a union type can hold one value of any type that is declared in the union. Use the member-...
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A C union type can contain only data members. In C, you must use the union keyword to declare a union variable. In C++, the union keyword is unnecessary: Example 1 union UNKNOWN var2; // C declaration of a union variable UNKNOWN var3; // C++ declaration of a union variable ...
cannot be used as a baseclass,nor can it have base classes.Default access of members in aunionispublic. A Cuniontype can contain only data members. In C,you must use theunionkeyword to declare aunionvariable.In C++,theunionkeyword is unnecessary: ...
C = union([5 5 3],[1 2 5],'sorted') C = 1 2 3 5 'stable' The values (or rows) inCreturn in the same order as they appear inA, thenB. Example C = union([5 5 3],[1 2 5],'stable') C = 5 3 1 2 Data Types:char|string ...