学步园

/*#include  "opencv2/opencv.hpp"
#include  "opencv2/objdetect.hpp"
#include  "opencv2/highgui.hpp"
#include  "opencv2/imgproc.hpp"
#include  "opencv2/test.h"
*/

#include  <iostream>
using namespace std;
/*
 *test class override
 */
class father{
	public :
		int test(){return 1;}
		virtual int vtest(){return 1;}
};
class son:public father{
	public:
		int test(){return 2;}
		int vtest(){return 2;}
};
int test(father &f){
	return f.test();
}
int test(father *f){
	return f->test();
}
int vtest(father f,bool s){
	return f.vtest();
}
int vtest(father &f){
	return f.vtest();
}
int vtest(father *f){
	return f->vtest();
}
void test1(){
	son a;
	printf("test class overwrite:%d,%d,%d\n",a.test(),test(a),test(&a));
	printf("vtest class override:%d,%d,%d\n",a.vtest(),vtest(a),vtest(&a));
	printf("vtest class override:%d\n",vtest(a,true));
}
/*
 * test pointer
 */
void test2(){
	int b[2]={1,2};
	int *a=b;
	cout<<a[1]<<":"<<*(a+1)<<endl;
}
/*
 * test int and unsigned int's operator >
 * 要防止用int负数跟unsigned数进行比较
 * 否则int负数就会被当成unsigned数
 */
void test3(){
	int a=-1;
	size_t b=1;
	cout<<"a=-1,b=unsigned 1"<<endl;
	cout<<"a>(size_t)b ? :"<<(a>b)<<endl<<"a>(int)b ?:"<<(a>(int)b)<<endl;
	vector<int> s={};
	//ERROR: 
	//unsigned 0 -1 = unsigned ....
	//i<-1 overflow
	for(int i=0;i<(int)(s.size()-1);i++){
		s[i]=0;
	}
	for(int i=0;i<(int)s.size()-1;i++){
		s[i]=0;
	}
}
/*
 * test stl vector and xxx_bound
 */
void test4(){
	vector<int> s={5,4,3,2,1};
	vector<int>::iterator it=lower_bound(s.begin(),s.end(),7,greater<int>());
	cout<<"lower bound bigger than 7:"<<*it<<endl;
	it=lower_bound(s.begin(),s.end(),4,greater<int>());
	cout<<"lower bound bigger than 4:"<<*it<<endl;
	it=upper_bound(s.begin(),s.end(),4,greater<int>());
	cout<<"upper bound bigger than 4:"<<*it<<endl;
	it=lower_bound(s.begin(),s.end(),4,less<int>());
	cout<<"lower bound smaller than 4:"<<*it<<endl;
}
/*
 *test bit algorithm
 */
void test5(){
	unsigned int a=((unsigned int)(~0))/2;
	int b=(~0)>>1;
	printf("%x:%x\n",a,b);
	int c=1<<2+3;
	cout<<c<<endl;
}
/*
 * test stl map and list
 */
void test6(){
	map<int,int> s;
	s.erase(2);
	list<int> l={1,2};
	typedef list<int>::iterator It;
	It it=l.begin();it++;it=++l.begin();
	cout<<*it<<endl;
	//ERROR: l.begin()+n 
	//for list iterator don't support +/- n operation
}


int main(){
	test3();
	test4();
	test5();
	test6();
	return 0;
}