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 tim
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...
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-...
More Sign in Auto Union Type C (6.0) specsCar type Open-wheeler Curb weight 734 kg (1618 lbs) Years built 1936 - 1937 Origin country Germany Views 421 Submitted by LotusFanPowertrain specs Engine type V16 Displacement 6.0 l (366 ci / 6005 cc) Power 527 ps (520 bhp / 388 kw) @...
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: ...
the values (or rows) inBthat contribute to the union. If there is a repeated value (or row) appearing exclusively inB, thenibcontains the index to the first occurrence of the value. If a value (or row) appears in bothAandB, thenibdoes not contain an index to the value (or row)....
“代数数据类型(Algebraic Data Type, ADT)” 模式匹配(Pattern Matching) 更多Tagged Union 你可能时常听到有人谈到一个叫做“Tagged union(标记联合体)”的概念,并告诉你很多编程语言里的概念(比如“和类型(Sum type)”)本质上就是 Tagged union——这似乎有些故弄玄虚的意味,乍一听你也许感觉自己好像用不上这么...