我目前正在学习Accelerated C++，我有点难以理解我必须将#include放在哪里(无论是在头文件和/或源文件中)，最重要的是，我是否是多余的。
我很感激所有关于我应该改变什么和不必要的评论。我觉得我多次包含库(例如，如果主程序有#include，我需要在任何其他头/源文件中包含它吗？)。此外，如果使用
#include "Student_info.h"
并且Student_info.cpp文件包括grade.h，我还需要在main.cpp中包含grade.h吗？我发布这段代码是因为我认为应用程序到一个特定的例子将是在我的头脑中演练组织这些文件的正确方式的最佳方式，也是我应该注意的常见错误
文件列表-为了完整性，我包括了整个代码，但只有最重要的部分和原则才是
main.cpp
#include<iostream>
#include<string>
#include<ios>
#include<stdexcept>
#include<vector>
#include<algorithm>
#include<iomanip>
#include "grade.h"
#include "Student_info.h"
#include "analysis.h"
using std::cin; using std::setprecision;
using std::cout; using std::sort;
using std::domain_error; using std::streamsize;
using std::endl; using std::string;
using std::max; using std::vector;
int main()
{
//students who did and didn't do their homework
vector<Student_info> did, didnt;
//read the student records and partition them
Student_info student;
while (read(cin,student))
{
if (did_all_hw(student))
did.push_back(student);
else
didnt.push_back(student);
}
//verify that the analyses will show us something
if (did.empty())
{
cout<<"No student did all the homework!"<<endl;
return 1;
}
if (didnt.empty())
{
cout<<"Every student did all the homework!"<<endl;
return 1;
}
//do the analyses
write_analysis(cout, "median",median_analysis, did, didnt);
write_analysis(cout, "average",average_analysis, did, didnt);
write_analysis(cout, "median of homework turned in", optimistic_median_analysis, did, didnt);
return 0;
}
等级.h
#ifndef GUARD_grade_h
#define GUARD_grade_h
//grade.h - Header file
#include<vector>
#include "Student_info.h"
double grade(double, double, double);
double grade(double, double, const std::vector<double>&);
double grade(const Student_info&);
bool fgrade(const Student_info& s);
bool pgrade(const Student_info& s);
double grade_aux(const Student_info& s);
double average(const std::vector<double>& v);
double average_grade(const Student_info& s);
double optimistic_median(const Student_info& s);
#endif
等级.cpp
#include<stdexcept>
#include<vector>
#include<numeric>
#include "grade.h"
#include "median.h"
#include "Student_info.h"
using std::domain_error;
using std::vector;
//reference to constant vector of type double
//vector<double> homework
//vector<double>& hw = homework; (this means that hw is a synonym for homework)
//This function is a ALSO called grade
//This is OVERLOADING and the argument list will be checked to decide which function to call
//The & asks the implementation NOT to copy its argument and const means don't change it
double grade(double midterm, double final, const vector<double>& hw)
{
if (hw.size()==0)
throw domain_error("student has done no homework");
return grade(midterm,final,median(hw));
}
double grade(double midterm, double final, double homework)
{
return 0.2*midterm+0.4*final+0.4*homework;
}
//because it's a reference variable, there is no overboard in copying the object
//and modifying it in the function modifies the original variable passed in
//returns double representing OVERALL GRADE
double grade(const Student_info& s)
{
return grade(s.midterm,s.final,s.homework);
}
bool fgrade(const Student_info& s)
{
return grade(s) < 60;
}
bool pgrade(const Student_info& s)
{
return !fgrade(s);
}
//need this function because the transform function can't use grade as there are too many overloaded versions
//and it doesn't know which one to call
double grade_aux(const Student_info& s)
{
try {
return grade(s);
}
catch (domain_error)
{
return grade(s.midterm, s.final, 0);
}
}
//Write the average function to use for average_analysis
double average(const vector<double>& v)
{
//accumulate is defined in the <numeric> library
//The accumulate function adds the values in range denoted by the first two arguments, starting with the
//the value given by the third argument (which also gives the resulting type, e.g. 0.0 will make accumulate return a double
return accumulate(v.begin(),v.end(),0.0)/v.size();
}
double average_grade(const Student_info& s)
{
return grade(s.midterm,s.final, average(s.homework));
}
double optimistic_median(const Student_info& s)
{
vector<double> nonzero;
//extracts nonzero vectors from the homework vector and appends them to (vector<double> nonzero)
remove_copy(s.homework.begin(), s.homework.end(),
back_inserter(nonzero),0);
if (nonzero.empty())
return grade(s.midterm,s.final,0);
else
return grade(s.midterm, s.final,median(nonzero));
}
分析.h
#ifndef GUARD_output_analysis
#define GUARD_output_analysis
//output_analysis.h - header file
#include<iostream>
#include<vector>
#include<iterator>
#include "Student_info.h"
#include "grade.h"
#include "median.h"
using std::ostream; using std::string;
void write_analysis(ostream& out,
const string& name,
double analysis(const vector<Student_info>&),
const vector<Student_info>& did,
const vector<Student_info>& didnt);
double median_analysis(const vector<Student_info>& students);
double average_analysis(const vector<Student_info>& students);
double optimistic_median_analysis(const vector<Student_info>& students);
#endif
分析.cpp
#include<iterator>
#include<algorithm>
#include "Student_info.h"
#include "grade.h"
#include "median.h"
using std::istream; using std::vector;
using std::ostream; using std::string;
using std::endl; using std::transform;
void write_analysis(ostream& out,
const string& name,
double analysis(const vector<Student_info>&),
const vector<Student_info>& did,
const vector<Student_info>& didnt)
{
out <<name <<" : median(did) = "<<analysis(did)
<<", median(didnt) = "<<analysis(didnt)<<endl;
}
double median_analysis(const vector<Student_info>& students)
{
vector<double> grades;
//The function grade is applied to every element in the range students.begin() to students.end()
//and this is appended to the end of the grades vector
transform(students.begin(), students.end(), back_inserter(grades), grade_aux);
return median(grades);
}
double average_analysis(const vector<Student_info>& students)
{
vector<double> grades;
//recall that tranform applies the average_grade function to every element between students.begin() and students.end()
//and appends this to the end of the grade vector (which is where the iterator returned by back_inserter(grades) points to
transform(students.begin(), students.end(),
back_inserter(grades), average_grade);
return median(grades);
}
double optimistic_median_analysis(const vector<Student_info>& students)
{
vector<double> grades;
transform(students.begin(),students.end(), back_inserter(grades),optimistic_median);
return median(grades);
}
中值h
#ifndef GUARD_median_h
#define GUARD_median_h
//median.h
#include<vector>
double median(std::vector<double>);
#endif
中值.cpp
#include "median.h"
using std::vector;
using std::sort;
using std::domain_error;
double median(vector<double> vec)
{
typedef vector<double>::size_type vec_sz;
vec_sz size=vec.size();
//if the vector is empty, an exception is thrown
//execution stops and passes to another part of the program
//along with the exception object
if (size==0)
throw domain_error("median of an empty vector");
sort(vec.begin(),vec.end());
vec_sz mid = size/2;
return size%2==0 ? ((vec[mid]+vec[mid-1])/2) : (vec[mid]);
}
Student_info.h
#ifndef GUARD_Student_info
#define GUARD_Student_info
//Student_info.h header file
#include<iostream>
#include<string>
#include<vector>
using std::vector;
struct Student_info {
std::string name;
double midterm,final;
std::vector<double> homework;
};
bool compare(const Student_info&, const Student_info&);
bool did_all_hw(const Student_info& s);
bool pgrade(const Student_info& s);
std::istream& read(std::istream&, Student_info&);
std::istream& read_hw(std::istream&, std::vector<double>&);
vector<Student_info> extract_fails(vector<Student_info>& students);
#endif
Student_info.cpp
//Source file for Student_info related functions
#include "Student_info.h"
#include "grade.h"
using std::istream; using std::vector;
bool compare(const Student_info& x, const Student_info& y)
{
return x.name < y.name;
}
istream& read(istream& is, Student_info& s)
{
//read and store the student's name and midterm and final exam grades
is >> s.name >> s.midterm >> s.final;
read_hw(is, s.homework); //read AND store all the student's homework grades
return is;
}
istream& read_hw(istream& in, vector<double>& hw)
{
if (in) {
//remove previous contents and leaves us with an empty vector
hw.clear();
double x;
while (in>>x)
hw.push_back(x);
//clear the stream so that input will work for the next student
//reset any error indicatiosn so that input can continue
in.clear();
}
//this means we were given an object that we're NOT going to a copy and we will
//return the object without copying it
return in;
}
bool did_all_hw(const Student_info& s)
{
//recall that if 0 is not found in the sequence given by the first two iterators, then the 2nd argument is returned
return ((find(s.homework.begin(), s.homework.end(), 0)) == s.homework.end());
}
//ONE-PASS SOLUTION
vector<Student_info> extract_fails(vector<Student_info>& students)
{
vector<Student_info>::iterator iter=stable_partition(students.begin(),students.end(),pgrade);
vector<Student_info> fail(iter,students.end()); //vector consisting of all failing elements
students.erase(iter,students.end());
return fail;
}
只有当编译器需要知道您正在使用的类型的大小，或者您试图访问它的任何成员或方法(包括您尚未显式创建的方法，如默认构造函数、析构函数或赋值运算符)时，才需要包含头文件。在Grade.h中，您不需要#include "Student_info.h"，因为Student_info是一个参考。您可以使用正向声明：
class Student_info; // Don't #include it, forward declare it
此外，您几乎不需要编写头保护，因为所有现代编译器都支持#pragma once，它在编译过程中只包含该文件一次。