C++中有多少关键字
asm auto bad_cast bad_typeidbool break case catchchar class const const_castcontinue default delete dodouble dynamic_cast else enumexcept explicit extern falsefinally float for friendgoto if inline intlong mutable namespace newoperator private protected publicregister reinterpret_cast return shortsigned sizeof static static_caststruct switch template thisthrow true try type_infotypedef typeid typename unionunsigned using virtual voidvolatile wchar_t while(1)asmasm已经被__asm替代了,用于汇编语言嵌入在C/C++程序里编程,从而在某些方面优化代码.虽然用asm关键字编译时编译器不会报错,但是asm模块的代码是没有意义的.(2)auto 这个这个关键字用于声明变量的生存期为自动,即将不在任何类、结构、枚举、联合和函数中定义的变量视为全局变量,而在函数中定义的变量视为局部变量。
这个关键字不怎么多写,因为所有的变量默认就是auto的。(3)bad_cast,const_cast,dynamic_cast,reinterpret_cast,static_cast关于异常处理的,还不是太了解..(4)bad_typeid也是用于异常处理的,当typeid操作符的操作数typeid为Null指针时抛出.(5)bool不用多说了吧,声明布尔类型的变量或函数.(6)break跳出当前循环.The break statement terminates the execution of the nearest enclosing loop or conditional statement in which it appears. (7)caseswitch语句分支.Labels that appear after the case keyword cannot also appear outside a switch statement. (8)catch,throw,try都是异常处理的语句,The try, throw, and catch statements implement exception handling.(9)char声明字符型变量或函数.(10)class声明或定义类或者类的对象.The class keyword declares a class type or defines an object of a class type.(11)const被const修饰的东西都受到强制保护,可以预防意外的变动,能提高程序的健壮性。
它可以修饰函数的参数、返回值,甚至函数的定义体。 作用: 1.修饰输入参数 a.对于非内部数据类型的输入参数,应该将“值传递”的方式改为“const引用传递”,目的是提高效率。
例如将void Func(A a) 改为void Func(const A &a)。 b.对于内部数据类型的输入参数,不要将“值传递”的方式改为“const引用传递”。
否则既达不到提高效率的目的,又降低了函数的可理解性。例如void Func(int x) 不应该改为void Func(const int &x)。
2.用const修饰函数的返回值 a.如果给以“指针传递”方式的函数返回值加const修饰,那么函数返回值(即指针)的内容不能被修改,该返回值只能被赋给加const修饰的同类型指针。 如对于:const char * GetString(void); 如下语句将出现编译错误: char *str = GetString();//cannot convert from 'const char *' to 'char *'; 正确的用法是: const char *str = GetString(); b.如果函数返回值采用“值传递方式”,由于函数会把返回值复制到外部临时的存储单元中,加const修饰没有任何价值。
如不要把函数int GetInt(void) 写成const int GetInt(void)。 3.const成员函数的声明中,const关键字只能放在函数声明的尾部,表示该类成员不修改对象. 说明: const type m; //修饰m为不可改变 示例: typedef char * pStr; //新的类型pStr; char string[4] = "abc"; const char *p1 = string; p1++; //正确,上边修饰的是*p1,p1可变 const pStr p2 = string; p2++; //错误,上边修饰的是p2,p2不可变,*p2可变 同理,const修饰指针时用此原则判断就不会混淆了。
const int *value; //*value不可变,value可变 int* const value; //value不可变,*value可变 const (int *) value; //(int *)是一种type,value不可变,*value可变 //逻辑上这样理解,编译不能通过,需要tydef int* NewType; const int* const value;//*value,value都不可变(12)continue结束当前循环,开始下一轮循环.Forces transfer of control to the controlling expression of the smallest enclosing do, for, or while loop. (13)defaultswitch语句中的默认分支.None of the constants match the constants in the case labels; a default label is present.Control is transferred to the default label.(14)delete经常用于动态内存分配的语句,Deallocates a block of memory. (15)do在do-while循环结构中开始循环体.Executes a statement repeatedly until the specified termination condition (the expression) evaluates to zero.(16)double声明双精度变量或函数.(17)else条件语句否定分支(与 if 连用).(18)enum声明枚举类型.The name of each enumerator is treated as a constant and must be unique within the scope where the enum is defined. (19)explicitThis keyword is a declaration specifier that can only be applied to in-class constructor declarations. An explicit constructor cannot take part in implicit conversions. It can only be used to explicitly construct an object. (20)exportMSDN只说The export keyword is not supported on templates.一种导出语句吧..(21)externextern 意为“外来的”···它的作用在于告诉编译器:有这个变量,它可能不存在当前的文件中,但它肯定要存在于工程中的某一个源文件中或者一个。
const std::string &getId() const {return id;}这句话中的“&"是什么意
首先来解释 下这里面有 的两个 CONST ,第一个 与 STD::STRING 在一起, 就像 CONST INT 一样,,只不过这里 INT 换成了 STD::STRING 而以,,第二个CONST 表示在 这个GETID 函数 不会对调用者数据造成修改 。MSDN 中的解释 如下:
const
const declaration
member-function const
When modifying a data declaration, the const keyword specifies that the object or variable is not modifiable. When following a member function's parameter list, the const keyword specifies that the function doesn't modify the object for which it is invoked.
然后再来说下 引用:在C++ PRIMER 4 里面有 跟下面 差不多的话,
CONST引用与非CONST引用
我们可以定义变量如:
INT I=10; 同理可以定义其引用如:
INT & REFI=I; (1) 这样,我们就可以操纵这个引用了,可以通过REFI 来修改I 的值。
通过上面的例子,我们要明白,非CONST引用可以修改它绑定的值。
同理:
我们可以定义CONST对象如:
CONST INT I=10;
同理我们可以定义引用来绑定到这个CONST对象 如:
INT & REFI =I;(2)
比较(1)(2)两个表达式,是一样的,也就是说在表达式(2) 定义完之后,我们同样可以通过REFI 改变 I的值。这与我们的I 被定义成 CONST 是相违背的。所以我们规定:
将非CONST引用绑定到CONST对象是不合法的。
CONST引用可以初始化为不同类型的对象或者右值,如字面值常量。
非CONST引用只能绑定到与该引用同类型的对象。
CONST引用则可以绑定到不同但相关的类型的对象或绑定到右值。
以上部分摘自C++ PRIMER 4
解释了引用 CONST引用 与 非CONST引用
所以 说 还是要 仔细的看书,,,
你这里面的 &; 表示 的是 引用 。而且 是 CONST 引用。
英语完型填空,求学霸解答
网上找到的原文,望采纳,谢谢~
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The most w7 things about the Internet is that everyone on it is equal.Afive-year-old in China can get the same i8 as a NASA scientist in Houston.Another amazing thing is that no one o9 the Internet--no person,no g10, no organization, and no business.
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看一下下面这段话有没有语法错误
有些错误,不过大致上已经很好啦!
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Now, everybody knows that sports is a very important part of our life. But what is the best way to exercise? Mr. Handsome has the answer!
First of all, lots of people thinks that the best time to exercise is in the morning, around half past five to eight o'clock. But NOT any sooner! Especially, during the autumn and winter times. Cold weather can cause diseases and colds(感冒).
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俺添加了一些句子,让听者或读者较容易明白。希望您不不介意。希望有帮助。
C++中函数的返回值为const类型的作用
If you are returning an object of a user-defined type by value as a const, it means the returned value cannot be modified. If you are passing and returning addresses, const is a promise that the destination of the address will not be changed.。
谁有学习C语言方面的英语书介绍几本
我的大学教材是 C语言程序设计(英文版·第3版) 作 者 [美]Stephen G.Kochan 著 出 版 社 人民邮电出版社 C语言程序设计(英文版·第3版) 目录 Table of Contents1 introduction 12 SomeFundamentals 5Programming 5Higher-Level Languages 6Operating Systems 6Compiling Programs 7Integrated Development Environments 10Language Interpreters 103 Compiling and Running Your First Program 11Compiling Your Program 11RunningYour Program 12Understanding Your First Program 13Displaying the Values of Variables 15Comments 17Exercises 194 Variables, Data Types, and Arithmetic Expressions 21Working with Variables 21Understanding Data Types and Constants 23 The Basic IntegerType int 23 The Floating Number Type f loat 24 The Extended Precision Type double 25 The Single Character Type char 25 The Boolean DataType Bool 26 Type Specifiers: long, long long, short, unsigned, and signed 28Working with Arithmetic Expressions 30 Integer Arithmetic and the Unary Minus Operator 33 The Modulus Operator 35 Integer and Floating-Point Conversions 36Combining Operations with Assignment: The Assignment Operators 38Types, Complex and Imaginary 39Exercises 405 Program Looping 43The for Statement 44 Relational Operators 46 Aligning Output 50 Program Input 51 Nested for Loops 53 for LoopVariants 54The while Statement 56The do Statement 60 The break Statement 62 The continue Statement 62Exercises 636 Making Decisions 65The if Statement 65 The if-else Construct 69 Compound Relational Tests 72 Nested if Statements 75 The else if Construct 76The switch Statement 84Boolean Variables 87The Conditional Operator 91Exercises 937 Working with Arrays 95Defining an Array 96 Using Array Elements as Counters 100 Generating Fibonacci Numbers 103 Using an Array to Generate Prime Numbers 104Initializing Arrays 106Character Arrays 108 Base Conversion Using Arrays 109 The c onst Qualifier 111Multidimensional Arrays 113Variable-Length Arrays 115Exercises 1178 Working with Functions 119Defining a Function 119Arguments and LocalVariables 122 Function Prototype Declaration 124 Automatic LocalVariables 124Returning Function Results 126Functions Calling Functions Calling。
131 Declaring Return Types and Argument Types 134 Checking Function Arguments 135Top-Down Programming 137Functions and Arrays 137 Assignment Operators 142 Sorting Arrays 143 Multidimensional Arrays 146GlobalVariables 152Automatic and Static Variables 156Recursive Functions 159Exercises i629 Working with Structures 165A Structure for Storing the Date 166 Using Structures in Expressions 168Functions and Structures 171 A Structure for Storing theTime 177Initializing Structures 180 Compound Literals 181Arrays of Structures 182Structures Containing Structures 185Structures Containing Arrays 187Structure Variants 190Exercises 19110 Character Strings 195Arrays of Characters 196Variable-Length Character Strings 198 Initializing and Displaying Character Strings 201 Testing Two Character Strings for Equality 204 Inputting Character Strings 206 Single-Character Input 208 The Null String 213Escape Characters 216More on Constant Strings 218Character Strings, Structures, and Arrays 219 A Better Search Method 222Character Operations 227Exercises 23011 Pointers 235Defining a Pointer Variable 235Using Pointers in Expressions 239Working with Pointers and Structures 240 Structures Containing Pointers 243 Linked Lists 244The Keyword const and Pointers 253Pointers and Functions 254Pointers and Arrays 259 A Slight Digression About Program Optimization 263 Is It an Array or Is It a Pointer? 264 Pointers to Character Strings 266 Constant Character Strings and Pointers 267 The Increment and Decrement Operators Revisited 268Operations on Pointers 272Pointers to Functions 273Pointers and Memory Addresses 274Exercises 27612 Operations on Bits 279Bit Operator-s 280The Bitwise AND Operator 281The Bitwise Inclusive-OR Operator 283The Bitwise Exclusive-OR Operator 284The Ones Complement Operator 285The Left Shift Operator 287The Right Shift Operator 287A Shift Function 288Rotating Bits 290Bit Fields 292Exercises 29713 The Preprocessor 299The #define Statement 299Program Extendability 303Program Portability 305More Advanced Types of Definitions 306The # Operator 312The ## Operator 313The #include Statement 313System Include Files 316Conditional Compilation 316The #ifdef, #endif, #else, and #。
Today the world of communication is changing,and the keyword is
Today the world of communication is changing,and the keyword is Internet.It is the fastest-growing means of c1 in history.
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The most w7 things about the Internet is that everyone on it is equal.Afive-year-old in China can get the same i8 as a NASA scientist in Houston.Another amazing thing is that no one o9 the Internet--no person,no g10, no organization, and no business.
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6、why 7、wonderful 8、information 9、own 10、government
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