c++ primer(第五版)习题答案代码版(第六章)函数
2018-01-16 22:21
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本文为转载,原博客地址:http://blog.csdn.net/refuil/article/details/51346844
习题答案至于一个.cc 中,编译需要包含Chapter6.h头文件。 需要演示某一题直接修改 #define NUM***, 如运行6.23题为#define NUM623;
#ifndef CHAPTER6_H
#define CHAPTER6_H
int fact(int val);
int func();
template <typename T> T abs(T val){
return val >= 0 ? val : -val;
}
#endif
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#include <iostream>
#include "Chapter6.h"
using namespace std;
int main(){
cout << "5! is "<<fact(5)<<endl;
cout << func() <<endl;
cout << abs(-2.34) <<endl;
}
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#include <iostream>
#include "Chapter6.h"
using namespace std;
int fact(int val){
if(val == 0 || val ==1)
return 1;
else
return val * fact(val-1);
}
int func(){
int n, ret =1;
cout<< "Enter a number: "<<endl;
cin >> n;
while(n > 1)
ret *= n--;
return ret;
}
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#include <iostream>
#include <vector>
#include <cstring>
#include <cassert>
#include "Chapter6.h"
#define NUM648
#define NDEBUG
using namespace std;
/*6.3*/
int fact(int val){
if(val == 0 || val ==1)
return 1;
else
return val * fact(val-1);
}
/*6.4*/
int fact2(){
int val;
cout << "Enter a number: "<<endl;
while(cin >> val){
if( val == 0 || val < 0)
cout<<"Please input a positive number. "<<endl;
cout<< val;
unsigned long long exp = 1;
exp = fact(val);
cout<< "! is: ";
if(exp)
cout << exp <<endl;
else
cout<< "too big. "<<endl;
}
}
/*6.5*/
#ifdef NUM65
template <typename T>
T abs(T val){
return val > 0 ? val : -val;
}
#endif
/*6.6*/
int temp(int val1){
static int val2 = 0;
val2 += val1;
return val2;
}
/*6.7*/
int func(){
static int flag = 0;
return flag++;
}
/*6.10*/
void swap(int *val1, int *val2){
int temp;
temp = *val1;
*val1 = *val2;
*val2 = temp;
}
/*6.11*/
void reset(int &val){
val = 0;
}
/*6.12*/
void swap2(int &val1, int &val2){
int temp;
temp = val1;
val1 = val2;
val2 = temp;
}
/*6.17*/
bool hasUpper(string &s){
for(string::iterator it = s.begin(); it != s.end(); ++it){
if(isupper(*it))
return true;
else
return false;
}
}
void changTolower(string& s){
for(size_t it = 0; it != s.size()-1; ++it){
if(isupper(s[it])){
s[it] = tolower(s[it]);
}
}
}
/*6.18*/
class matrix;
bool compare(matrix &ma1, matrix &ma2);
vector<int>::iterator change_val(int, vector<int>::iterator);
/*6.21*/
int contrast(const int val1, const int *p){
return val1 > *p ? val1 : *p;
}
/*6.22*/
void swap3(int*& val1, int*& val2){
int* temp;
temp = val1;
val1 = val2;
val2 = temp;
}
/*6.23*/
void print(const int *p){
if(p)
cout<< *p <<endl;
}
void print(int size, int str[]){
for(size_t it = 0; it!= size; ++it)
cout<< str[it] << endl;
}
void print(const int* beg, const int* end){
for(; beg!= end; )
cout<< *beg++ <<endl;
}
void print(int(&arr)[2]){
for(int i =0; i<= 1; ++i)
cout<< arr[i]<<endl;
}
/*6.27*/
#ifdef NUM627
int sum(initializer_list<int> li){
int sum(0);
for(initializer_list<int>::iterator beg = li.begin(); beg!= li.end(); ++beg)
sum += *beg;
return sum;
}
#endif
/*6.30*/
#ifdef NUM630
bool str_subrange(const string &str1, const string &str2){
if(str1.size() == str2.size())
return str1 == str2;
size_t size = str1.size() < str2.size() ? str1.size() : str2.size();
for(size_t i =0; i!= size; ++i){
if(str1[i] != str2[i])
return;
}
}
#endif
/*6.33*/
int &get(vector<int> &ia, int index){ return ia[index]; }
void print(vector<int>::iterator beg, vector<int>::iterator end){
if(beg != end){
cout << *beg <<" ";
print(next(beg), end);
}
}
/*6.35*/
int factorial(int val){
if(val > 1)
return factorial(val -1) * val;
return 1;
}
/*6.36*/
string (&func2(string (&str)[10]))[10];
/*6.37*/
#ifdef NUM637
typedef string arrT[10];
arrT &func3(arrT& str);
auto func4(arrT& str) -> string(&)[10];
string arrS[10];
decltype(arrS)& func5(arrT& str);
#endif
/*6.38*/
int odd[] = {1,3,5,7,9};
int even[] = {0,2,4,6,8};
typedef int arrInt[5];
arrInt& arrPtr(int i){
return (i % 2) ? odd : even; //返回引用
}
/*6.42*/
string make_plural(size_t ctr, const string& word, const string &ending = "s"){
return (ctr > 1) ? word + ending : word;
}
/*6.44*/
inline bool isShorter(const string &s1, const string &s2){
return s1.size() < s2.size();
}
#ifdef NUM646
/*6.46*/
constexpr bool isShorter1(const string &s1, const string &s2){
return s1.size() < s2.size();
}
#endif
/*6.47*/
#ifdef NUM647
void printVector(vector<int>& vec){
#ifdef NDEBUG
cout << "vector size: " << vec.size() <<endl;
#endif
if(!vec.empty()){
auto temp = vec.back();
vec.pop_back();
printVector(vec);
cout << temp <<" ";
}
}
#endif
/*6.51*/
#ifdef NUM651
void f(){
cout << "f()"<<endl;
}
void f(int){
cout << "f(int)"<<endl;
}
void f(int, int){
cout << "f(int, int)"<<endl;
}
void f(double, double = 3.14){
cout << "f(duble, double)"<<endl;
}
#endif
/*6.54*/
typedef int func6(int, int);
vector<func6*> vec;
/*6.55*/
int add(int a, int b){
return a + b;
}
int substact(int a, int b){
return a - b;
}
int multiply(int a, int b){
return a * b;
}
int divide(int a, int b){
return b !=0 ? a/b : 0;
}
int main(){
/*6.1*/
#ifdef NUM61
cout<<"实参是形参的初始值,实参的类型必须与对应的形参类型匹配。"<<endl;
#endif
/*6.2*/
#ifdef NUM62
cout<<"(a)返回类型不匹配,int型改成string;(b)没有定义函数的返回类型,可以用void代替; (c)缺少一个括号; (d)函数体缺少一对括号."<<endl;
#endif
/*6.3*/
#ifdef NUM63
cout << "5!: " << fact(5) <<endl;
#endif
/*6.4*/
#ifdef NUM64
fact2();
#endif
/*6.5*/
#ifdef NUM66
cout << "The absolute of -2.34 is: "<< abs(-2.34)<<endl;
#endif
/*6.6*/
#ifdef NUM66
cout<< "形参的生命周期是从函数开始到函数终止即被销毁,局部变量的生命周期是从其被创建到函数体结束。静态局部变量在被初始化开始,直到程序结束才会被销毁。"<<endl;
for(int val3 =0; val3 !=10; ++val3)
cout << "静态变量与局部变量的和是: "<< temp(val3) <<endl;
#endif
/*6.7*/
#ifdef NUM67
for(int i =0; i!=4; ++i)
cout<< func()<<endl;
#endif
/*6.8*/
#ifdef NUM68
cout<<"见Chapter6.h" <<endl;
#endif
/*6.9*/
#ifdef NUM69
cout<<"见fact.cc factMain.cc" <<endl;
#endif
/*6.10*/
#ifdef NUM610
int val1 = 1, val2 = 2;
swap(&val1, &val2);
cout<< "val1: "<< val1 << " val2: " << val2<<endl;
#endif
/*6.11*/
#ifdef NUM611
int val = 23;
reset(val);
cout << "val has been reset: "<< val <<endl;
#endif
/*6.12*/
#ifdef NUM612
for(int val1(0), val2(0); cout<< "Enter two numbers: \n", cin >> val1 >> val2;){
swap2(val1, val2);
cout<< "val1: "<< val1 << " val2: " << val2<<endl;
}
#endif
/*6.13*/
#ifdef NUM613
cout<<"第一种是传值调用,调用过程中不会修改实参的值,第二种传地址引用调用,在调用过程中将会与实参的绑定。"<<endl;
#endif
/*6.14*/
#ifdef NUM614
cout<< "6.11例子中引用类型可以避免拷贝,但是在实参不希望被改变时不能使用引用形参."<<endl;
#endif
/*6.15*/
#ifdef NUM615
cout<<"首先,实参s不能够被改变,但是occur的最后值时通过函数计算的;c可能是一个临时变量,可以换成其他值;如果交换类型,s可以被改变,occur不能改变,=0,报错"<<endl;
#endif
/*6.16*/
#ifdef NUM616
cout<< "应该设置为const引用,因为s不希望被改变,可以避免拷贝,直接使用字符串常量作为参数. "<<endl;
#endif
/*6.17*/
#ifdef NUM617
string s = "C++ & Linux";
if(hasUpper(s)) cout << "has upper letter. "<<endl;
else cout << "no upper letter. "<<endl;
changTolower(s);
cout << "After tolower: " << s <<endl;
#endif
/*6.18*/
#ifdef NUM618
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.19*/
#ifdef NUM619
cout<< "(a)不合法,calc只有一个参数." <<endl;
#endif
/*6.20*/
#ifdef NUM620
cout<< "一般能用const都加上const,如果设为普通引用,可能在函数中会改变常量的值."<<endl;
#endif
/*6.21*/
#ifdef NUM621
int val1(2), val2(3);
cout << "return the larger: " << contrast(val1, &val2) << endl;
#endif
/*6.22*/
#ifdef NUM622
int val1(2), val2(3);
int* p1 = &val1; int* p2 = &val2;
swap3( p1, p2);
cout << "val1: " << *p1 << " val2: " << *p2 << endl;
#endif
/*6.23*/
#ifdef NUM623
int i =0, j[2] = {0, 1};
print(&i);
print(2, j);
print(begin(j), end(j));
print(j);
#endif
/*6.24*/
#ifdef NUM624
cout<<"没有什么问题,单数如果仅仅为了遍历数组,完全可以指针或引用的形式传递.如:"
" void print(const int (&ia)[10]) "<<endl;
#endif
/*6.25*/
#ifdef NUM625
cout<< "见main-6.25.cc"<<endl;
#endif
/*6.26*/
#ifdef NUM626
cout<< "见main-6.26.cc"<<endl;
#endif
/*6.27*/
#ifdef NUM627
cout << "Sum of 1-5: "<< sum( {1,2,3,4,5} ) <<endl;
#endif
/*6.28*/
#ifdef NUM628
cout << "elem 的类型是const string&"<<endl;
#endif
/*6.29*/
#ifdef NUM629
cout <<"因为initializer_list的元素总是 const类型,不能在函数内改变,应该声明为常量引用类型. "<<endl;
#endif
/*6.30*/
#ifdef NUM630
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.31*/
#ifdef NUM631
cout<< "返回局部变量的引用是无效的; 如果试图对返回常量引用类型赋值,也是无效的."<<endl;
#endif
/*6.32*/
#ifdef NUM632
cout<< "合法,作用是将0-9赋值给ia数组"<<endl;
#endif
/*6.33*/
#ifdef NUM633
vector<int> vec(10,0); //需要初始化,否则传参时会出错
for(int i =0; i != 10; ++i)
get(vec, i) = i;
print(vec.begin(), vec.end());
cout <<endl;
#endif
/*6.34*/
#ifdef NUM634
cout <<"如果val为负数,将发生堆栈溢出. "<<endl;
#endif
/*6.35*/
#ifdef NUM635
cout << factorial(5)<<endl;
cout <<" val--无法递归,报错 "<<endl;
#endif
/*6.36*/
#ifdef NUM636
cout<<"见main函数外函数声明, 第一种声明清晰,修改和阅读比较方便. "<<endl;
#endif
/*6.37*/
#ifdef NUM637
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.38*/
#ifdef NUM638
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.39*/
#ifdef NUM639
cout << "(a)非法,顶层const,重复声明. (b)非法,函数参数相同. (c)合法. "<<endl;
#endif
/*6.40*/
#ifdef NUM640
cout<< "(b)非法,一旦某个形参被赋予了默认值,它后面的所有形参都必须有默认值. "<<endl;
#endif
/*6.41*/
#ifdef NUM641
cout<< "(a)非法,没有给第一个形参传值. (b)合法. (c)合法,we被赋值为'*',但与意图不符. "<<endl;
#endif
/*6.42*/
#ifdef NUM642
cout << "singual: " << make_plural(1, "success", "es")<<" "<< make_plural(1, "failure")<<endl;
cout << "plural: " << make_plural(2, "success", "es")<<" "<< make_plural(2, "failure")<<endl;
#endif
/*6.43*/
#ifdef NUM643
cout <<"(a)内联函数放在头文件中. (b) 函数声明放在头文件中. "<<endl;
#endif
/*6.44*/
#ifdef NUM644
cout << isShorter("c++", "linux") <<endl;
#endif
/*6.45*/
#ifdef NUM645
cout << "内联函数的声明适合那些代码短小,并且容易经常被调用的函数. "<<endl;
#endif
/*6.46*/
#ifdef NUM646
cout << isShorter1("c++", "linux") <<endl;
#endif
/*6.47*/
#ifdef NUM647
vector<int> vec{1,2,3,4,5};
printVector(vec);
cout <<endl;
#endif
/*6.48*/
#ifdef NUM648
string s, sought("no");
while(cin >>s && s != sought){ }
assert(cin);
cout<< "不合理,因为cin输入总是有内容的,所以assert中的表达式总是为真,就不会执行assert. "<<endl;
#endif
/*6.49*/
#ifdef NUM649
cout << "函数匹配的第一步是选定本次调用对应的重载函数集,集合中的函数称为候选函数. 第二步考察本次调用提供的实参,然后从候选函数中选出能被这组实参调用的函数,这些新选出的函数称为可行函数. "<<endl;
#endif
/*6.50*/
#ifdef NUM650
cout << "(a) 2.56匹配double,但是42匹配int.(b)匹配void f(int). (c)匹配void f(int, int). (d)匹配void f(double, double = 3.14);"<<endl;
#endif
/*6.51*/
#ifdef NUM651
f(2.56, 42);
f(42);
f(42, 0);
f(2.56, 3.14);
#endif
/*6.52*/
#ifdef NUM652
cout << "(a)3, 通过类型提升实现的匹配. (b)4, 通过算术类型转换实现的匹配. "<<endl;
#endif
/*6.53*/
#ifdef NUM653
cout <<"(a)没有影响,const是顶层实现,第二句实现了函数重载. (b)非法,重复声明."<<endl;
#endif
/*6.54*/
#ifdef NUM654
cout <<"见main函数外声明. "<<endl;
#endif
/*6.55*/
#ifdef NUM655
vec.push_back(add);
vec.push_back(substact);
vec.push_back(multiply);
vec.push_back(divide);
for(vector<func6*>::iterator it = vec.begin(); it != vec.end(); ++it)
cout << (*it)(100, 50)<< " "; //*it两端的括号必不可少, 否则函数返回vector类型的指针, 而非函数指针.
cout <<endl;
#endif
return 0;
}
参考资料:
c++ primer中文版第五版,电子工业出版社。
c++ primer第四版习题解答,人民邮电出版社。
习题答案至于一个.cc 中,编译需要包含Chapter6.h头文件。 需要演示某一题直接修改 #define NUM***, 如运行6.23题为#define NUM623;
#ifndef CHAPTER6_H
#define CHAPTER6_H
int fact(int val);
int func();
template <typename T> T abs(T val){
return val >= 0 ? val : -val;
}
#endif
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#include <iostream>
#include "Chapter6.h"
using namespace std;
int main(){
cout << "5! is "<<fact(5)<<endl;
cout << func() <<endl;
cout << abs(-2.34) <<endl;
}
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#include <iostream>
#include "Chapter6.h"
using namespace std;
int fact(int val){
if(val == 0 || val ==1)
return 1;
else
return val * fact(val-1);
}
int func(){
int n, ret =1;
cout<< "Enter a number: "<<endl;
cin >> n;
while(n > 1)
ret *= n--;
return ret;
}
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#include <iostream>
#include <vector>
#include <cstring>
#include <cassert>
#include "Chapter6.h"
#define NUM648
#define NDEBUG
using namespace std;
/*6.3*/
int fact(int val){
if(val == 0 || val ==1)
return 1;
else
return val * fact(val-1);
}
/*6.4*/
int fact2(){
int val;
cout << "Enter a number: "<<endl;
while(cin >> val){
if( val == 0 || val < 0)
cout<<"Please input a positive number. "<<endl;
cout<< val;
unsigned long long exp = 1;
exp = fact(val);
cout<< "! is: ";
if(exp)
cout << exp <<endl;
else
cout<< "too big. "<<endl;
}
}
/*6.5*/
#ifdef NUM65
template <typename T>
T abs(T val){
return val > 0 ? val : -val;
}
#endif
/*6.6*/
int temp(int val1){
static int val2 = 0;
val2 += val1;
return val2;
}
/*6.7*/
int func(){
static int flag = 0;
return flag++;
}
/*6.10*/
void swap(int *val1, int *val2){
int temp;
temp = *val1;
*val1 = *val2;
*val2 = temp;
}
/*6.11*/
void reset(int &val){
val = 0;
}
/*6.12*/
void swap2(int &val1, int &val2){
int temp;
temp = val1;
val1 = val2;
val2 = temp;
}
/*6.17*/
bool hasUpper(string &s){
for(string::iterator it = s.begin(); it != s.end(); ++it){
if(isupper(*it))
return true;
else
return false;
}
}
void changTolower(string& s){
for(size_t it = 0; it != s.size()-1; ++it){
if(isupper(s[it])){
s[it] = tolower(s[it]);
}
}
}
/*6.18*/
class matrix;
bool compare(matrix &ma1, matrix &ma2);
vector<int>::iterator change_val(int, vector<int>::iterator);
/*6.21*/
int contrast(const int val1, const int *p){
return val1 > *p ? val1 : *p;
}
/*6.22*/
void swap3(int*& val1, int*& val2){
int* temp;
temp = val1;
val1 = val2;
val2 = temp;
}
/*6.23*/
void print(const int *p){
if(p)
cout<< *p <<endl;
}
void print(int size, int str[]){
for(size_t it = 0; it!= size; ++it)
cout<< str[it] << endl;
}
void print(const int* beg, const int* end){
for(; beg!= end; )
cout<< *beg++ <<endl;
}
void print(int(&arr)[2]){
for(int i =0; i<= 1; ++i)
cout<< arr[i]<<endl;
}
/*6.27*/
#ifdef NUM627
int sum(initializer_list<int> li){
int sum(0);
for(initializer_list<int>::iterator beg = li.begin(); beg!= li.end(); ++beg)
sum += *beg;
return sum;
}
#endif
/*6.30*/
#ifdef NUM630
bool str_subrange(const string &str1, const string &str2){
if(str1.size() == str2.size())
return str1 == str2;
size_t size = str1.size() < str2.size() ? str1.size() : str2.size();
for(size_t i =0; i!= size; ++i){
if(str1[i] != str2[i])
return;
}
}
#endif
/*6.33*/
int &get(vector<int> &ia, int index){ return ia[index]; }
void print(vector<int>::iterator beg, vector<int>::iterator end){
if(beg != end){
cout << *beg <<" ";
print(next(beg), end);
}
}
/*6.35*/
int factorial(int val){
if(val > 1)
return factorial(val -1) * val;
return 1;
}
/*6.36*/
string (&func2(string (&str)[10]))[10];
/*6.37*/
#ifdef NUM637
typedef string arrT[10];
arrT &func3(arrT& str);
auto func4(arrT& str) -> string(&)[10];
string arrS[10];
decltype(arrS)& func5(arrT& str);
#endif
/*6.38*/
int odd[] = {1,3,5,7,9};
int even[] = {0,2,4,6,8};
typedef int arrInt[5];
arrInt& arrPtr(int i){
return (i % 2) ? odd : even; //返回引用
}
/*6.42*/
string make_plural(size_t ctr, const string& word, const string &ending = "s"){
return (ctr > 1) ? word + ending : word;
}
/*6.44*/
inline bool isShorter(const string &s1, const string &s2){
return s1.size() < s2.size();
}
#ifdef NUM646
/*6.46*/
constexpr bool isShorter1(const string &s1, const string &s2){
return s1.size() < s2.size();
}
#endif
/*6.47*/
#ifdef NUM647
void printVector(vector<int>& vec){
#ifdef NDEBUG
cout << "vector size: " << vec.size() <<endl;
#endif
if(!vec.empty()){
auto temp = vec.back();
vec.pop_back();
printVector(vec);
cout << temp <<" ";
}
}
#endif
/*6.51*/
#ifdef NUM651
void f(){
cout << "f()"<<endl;
}
void f(int){
cout << "f(int)"<<endl;
}
void f(int, int){
cout << "f(int, int)"<<endl;
}
void f(double, double = 3.14){
cout << "f(duble, double)"<<endl;
}
#endif
/*6.54*/
typedef int func6(int, int);
vector<func6*> vec;
/*6.55*/
int add(int a, int b){
return a + b;
}
int substact(int a, int b){
return a - b;
}
int multiply(int a, int b){
return a * b;
}
int divide(int a, int b){
return b !=0 ? a/b : 0;
}
int main(){
/*6.1*/
#ifdef NUM61
cout<<"实参是形参的初始值,实参的类型必须与对应的形参类型匹配。"<<endl;
#endif
/*6.2*/
#ifdef NUM62
cout<<"(a)返回类型不匹配,int型改成string;(b)没有定义函数的返回类型,可以用void代替; (c)缺少一个括号; (d)函数体缺少一对括号."<<endl;
#endif
/*6.3*/
#ifdef NUM63
cout << "5!: " << fact(5) <<endl;
#endif
/*6.4*/
#ifdef NUM64
fact2();
#endif
/*6.5*/
#ifdef NUM66
cout << "The absolute of -2.34 is: "<< abs(-2.34)<<endl;
#endif
/*6.6*/
#ifdef NUM66
cout<< "形参的生命周期是从函数开始到函数终止即被销毁,局部变量的生命周期是从其被创建到函数体结束。静态局部变量在被初始化开始,直到程序结束才会被销毁。"<<endl;
for(int val3 =0; val3 !=10; ++val3)
cout << "静态变量与局部变量的和是: "<< temp(val3) <<endl;
#endif
/*6.7*/
#ifdef NUM67
for(int i =0; i!=4; ++i)
cout<< func()<<endl;
#endif
/*6.8*/
#ifdef NUM68
cout<<"见Chapter6.h" <<endl;
#endif
/*6.9*/
#ifdef NUM69
cout<<"见fact.cc factMain.cc" <<endl;
#endif
/*6.10*/
#ifdef NUM610
int val1 = 1, val2 = 2;
swap(&val1, &val2);
cout<< "val1: "<< val1 << " val2: " << val2<<endl;
#endif
/*6.11*/
#ifdef NUM611
int val = 23;
reset(val);
cout << "val has been reset: "<< val <<endl;
#endif
/*6.12*/
#ifdef NUM612
for(int val1(0), val2(0); cout<< "Enter two numbers: \n", cin >> val1 >> val2;){
swap2(val1, val2);
cout<< "val1: "<< val1 << " val2: " << val2<<endl;
}
#endif
/*6.13*/
#ifdef NUM613
cout<<"第一种是传值调用,调用过程中不会修改实参的值,第二种传地址引用调用,在调用过程中将会与实参的绑定。"<<endl;
#endif
/*6.14*/
#ifdef NUM614
cout<< "6.11例子中引用类型可以避免拷贝,但是在实参不希望被改变时不能使用引用形参."<<endl;
#endif
/*6.15*/
#ifdef NUM615
cout<<"首先,实参s不能够被改变,但是occur的最后值时通过函数计算的;c可能是一个临时变量,可以换成其他值;如果交换类型,s可以被改变,occur不能改变,=0,报错"<<endl;
#endif
/*6.16*/
#ifdef NUM616
cout<< "应该设置为const引用,因为s不希望被改变,可以避免拷贝,直接使用字符串常量作为参数. "<<endl;
#endif
/*6.17*/
#ifdef NUM617
string s = "C++ & Linux";
if(hasUpper(s)) cout << "has upper letter. "<<endl;
else cout << "no upper letter. "<<endl;
changTolower(s);
cout << "After tolower: " << s <<endl;
#endif
/*6.18*/
#ifdef NUM618
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.19*/
#ifdef NUM619
cout<< "(a)不合法,calc只有一个参数." <<endl;
#endif
/*6.20*/
#ifdef NUM620
cout<< "一般能用const都加上const,如果设为普通引用,可能在函数中会改变常量的值."<<endl;
#endif
/*6.21*/
#ifdef NUM621
int val1(2), val2(3);
cout << "return the larger: " << contrast(val1, &val2) << endl;
#endif
/*6.22*/
#ifdef NUM622
int val1(2), val2(3);
int* p1 = &val1; int* p2 = &val2;
swap3( p1, p2);
cout << "val1: " << *p1 << " val2: " << *p2 << endl;
#endif
/*6.23*/
#ifdef NUM623
int i =0, j[2] = {0, 1};
print(&i);
print(2, j);
print(begin(j), end(j));
print(j);
#endif
/*6.24*/
#ifdef NUM624
cout<<"没有什么问题,单数如果仅仅为了遍历数组,完全可以指针或引用的形式传递.如:"
" void print(const int (&ia)[10]) "<<endl;
#endif
/*6.25*/
#ifdef NUM625
cout<< "见main-6.25.cc"<<endl;
#endif
/*6.26*/
#ifdef NUM626
cout<< "见main-6.26.cc"<<endl;
#endif
/*6.27*/
#ifdef NUM627
cout << "Sum of 1-5: "<< sum( {1,2,3,4,5} ) <<endl;
#endif
/*6.28*/
#ifdef NUM628
cout << "elem 的类型是const string&"<<endl;
#endif
/*6.29*/
#ifdef NUM629
cout <<"因为initializer_list的元素总是 const类型,不能在函数内改变,应该声明为常量引用类型. "<<endl;
#endif
/*6.30*/
#ifdef NUM630
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.31*/
#ifdef NUM631
cout<< "返回局部变量的引用是无效的; 如果试图对返回常量引用类型赋值,也是无效的."<<endl;
#endif
/*6.32*/
#ifdef NUM632
cout<< "合法,作用是将0-9赋值给ia数组"<<endl;
#endif
/*6.33*/
#ifdef NUM633
vector<int> vec(10,0); //需要初始化,否则传参时会出错
for(int i =0; i != 10; ++i)
get(vec, i) = i;
print(vec.begin(), vec.end());
cout <<endl;
#endif
/*6.34*/
#ifdef NUM634
cout <<"如果val为负数,将发生堆栈溢出. "<<endl;
#endif
/*6.35*/
#ifdef NUM635
cout << factorial(5)<<endl;
cout <<" val--无法递归,报错 "<<endl;
#endif
/*6.36*/
#ifdef NUM636
cout<<"见main函数外函数声明, 第一种声明清晰,修改和阅读比较方便. "<<endl;
#endif
/*6.37*/
#ifdef NUM637
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.38*/
#ifdef NUM638
cout<<"见main函数外函数声明;"<<endl;
#endif
/*6.39*/
#ifdef NUM639
cout << "(a)非法,顶层const,重复声明. (b)非法,函数参数相同. (c)合法. "<<endl;
#endif
/*6.40*/
#ifdef NUM640
cout<< "(b)非法,一旦某个形参被赋予了默认值,它后面的所有形参都必须有默认值. "<<endl;
#endif
/*6.41*/
#ifdef NUM641
cout<< "(a)非法,没有给第一个形参传值. (b)合法. (c)合法,we被赋值为'*',但与意图不符. "<<endl;
#endif
/*6.42*/
#ifdef NUM642
cout << "singual: " << make_plural(1, "success", "es")<<" "<< make_plural(1, "failure")<<endl;
cout << "plural: " << make_plural(2, "success", "es")<<" "<< make_plural(2, "failure")<<endl;
#endif
/*6.43*/
#ifdef NUM643
cout <<"(a)内联函数放在头文件中. (b) 函数声明放在头文件中. "<<endl;
#endif
/*6.44*/
#ifdef NUM644
cout << isShorter("c++", "linux") <<endl;
#endif
/*6.45*/
#ifdef NUM645
cout << "内联函数的声明适合那些代码短小,并且容易经常被调用的函数. "<<endl;
#endif
/*6.46*/
#ifdef NUM646
cout << isShorter1("c++", "linux") <<endl;
#endif
/*6.47*/
#ifdef NUM647
vector<int> vec{1,2,3,4,5};
printVector(vec);
cout <<endl;
#endif
/*6.48*/
#ifdef NUM648
string s, sought("no");
while(cin >>s && s != sought){ }
assert(cin);
cout<< "不合理,因为cin输入总是有内容的,所以assert中的表达式总是为真,就不会执行assert. "<<endl;
#endif
/*6.49*/
#ifdef NUM649
cout << "函数匹配的第一步是选定本次调用对应的重载函数集,集合中的函数称为候选函数. 第二步考察本次调用提供的实参,然后从候选函数中选出能被这组实参调用的函数,这些新选出的函数称为可行函数. "<<endl;
#endif
/*6.50*/
#ifdef NUM650
cout << "(a) 2.56匹配double,但是42匹配int.(b)匹配void f(int). (c)匹配void f(int, int). (d)匹配void f(double, double = 3.14);"<<endl;
#endif
/*6.51*/
#ifdef NUM651
f(2.56, 42);
f(42);
f(42, 0);
f(2.56, 3.14);
#endif
/*6.52*/
#ifdef NUM652
cout << "(a)3, 通过类型提升实现的匹配. (b)4, 通过算术类型转换实现的匹配. "<<endl;
#endif
/*6.53*/
#ifdef NUM653
cout <<"(a)没有影响,const是顶层实现,第二句实现了函数重载. (b)非法,重复声明."<<endl;
#endif
/*6.54*/
#ifdef NUM654
cout <<"见main函数外声明. "<<endl;
#endif
/*6.55*/
#ifdef NUM655
vec.push_back(add);
vec.push_back(substact);
vec.push_back(multiply);
vec.push_back(divide);
for(vector<func6*>::iterator it = vec.begin(); it != vec.end(); ++it)
cout << (*it)(100, 50)<< " "; //*it两端的括号必不可少, 否则函数返回vector类型的指针, 而非函数指针.
cout <<endl;
#endif
return 0;
}
参考资料:
c++ primer中文版第五版,电子工业出版社。
c++ primer第四版习题解答,人民邮电出版社。
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