# include <iostream>
#include <string> 
#include <cmath>
#include <cstdlib>
#include <iomanip>
#include <fstream>
using namespace std;
//global variables (outside any function)
double c0,c1,c2,c3,c4;

int main(){
//increment, decrement : prefix vs postfix
	int n=1;
	cout<<"\nINCREMENT, DECREMENT : PREFIX vs POSTFIX\n n="<<n;
	++n;
	cout<<"    increased n="<<n;
	int m1=(n++);
	int m2=++n;
	cout<<"\npostfix m1="<<m1<<"    prefix m2="<<m2; 
	
//	return 0;
	
	n=0; int m3 = n+++ 1;
	n=0; int m4 = ++n+ 1;
	int m5 = 2* ++n * n++;	
	cout << "\n m3="<<m3<<"   m4="<<m4<<"   m5="<<m5<<"    n="<<n;

	cout << "\n";

//	return 0;

//*
//// while loops - counter
	cout<<"\n\n\n WHILE LOOP\n";
	int counter=0; 
	while (counter<10){
	//	counter++;
		cout<<"execution is at iteration "<<counter++<<"\n";
	}

	cout << "\n";
	
	
	//return 0;
///while loop -  validate input
	n=-1;
	while (n<0 || n>=10){
		cout<<"\n\n give me a non-negative integer less than 10>"; cin>>n;
	}
	cout<<"\n you gave me n="<<n;
	cout << "\n";
//	return 0;

////////////////////////////////////////////
///do-while loop -  validate input
	// cout<<"\n\n\nDO-WHILE LOOP\n";
	// n=-1;
	// do{
	// 	cout<<"\n\n give me a non-negative integer less than 10>"; cin>>n;
	// }while (n<0 || n>=10);
	// 
	// cout<<"\n you gave me n="<<n;
	// cout << "\n";

//	return 0;

//do-while loop - menu
	int selection;
do{
	cout<< "\n\n 1.Movies  2.Music  3.Pictures\n";
	cout<< "Please make a selection (1-3,0=exit):"; cin>>selection; 
	switch(selection) {
		case 1: //do some things with Movies; 
		cout<<"You selected Movies... ";
		cout<<"Favoite actor: Robert De Niro\n";
		break;
		case 2: //do some things with Music; 
			cout<<"You selected Music.";
			cout<<" Favorite song: Chan Chan by Compay Segundo\n";
		break;
		case 3: //do some things with Pictures
			cout<<"You selected Pictures. ";
			cout<<"Fovorite: Einstein portrait\n";
		break;
		case 0: 
			cout<<"exiting...";
		break;
		default: cout<< "Your selection is not valid\n";
			}	
}
while(selection<0 || selection>0);

			cout << "\n";


/////////////////////////////////////////////		
//for loop
 	int sum=0,t;
	//  	cout<<"\n\n FOR LOOP\n n="; cin>>n;
	//  	for(int i=1;i<=n;i++){
	//  		cout << "\n\n give me the "<<i<<" number>>"; cin>>t;
	//  		sum += t;
	//  		cout<< "  sum so far is "<<sum; 
	// } 
	//  	cout << "\n";

//	return 0;
//*/

//*
//break, continue
	sum=0;
	cout<<"\n\n FOR LOOP\n n="; cin>>n;
	for(int i=1;i<=n;i++){
		cout << "\n\n give me the "<<i<<" number(positive summed, upto sum=100)>>"; cin>>t;
		if (t<0){
			cout <<" ...negative. I am not summing it!"; continue;
		}
		sum+=t;
		cout<< "  sum so far is "<<sum; 
		if (sum>100){
			cout <<"  sum reached 100. No more numbers! (exit loop)"; 
			break; 
		}
	}
	cout << "\nloop finished.\n";

//	return 0;
	
	
//nested loops
	cout<<"\n\n NESTED LOOP\n";
	for (int i=1; i<=10; i++){
		cout<<"\n multiples of "<<i<<":  ";
		for (int j=1; j<=10; j++){
			cout <<i*j<<"  ";
		}
	}
//*/

//	return 0;






/////////////////////////////////////////////
//reading data from file

	fstream file;
	char ss[200]="polynomial.txt";
//	cout<<"filename="; cin.getline(ss,200);
	int a;
	file.open (ss);
	cout <<"\n\n\n READING DATA FROM FILE  file="<<ss<<"   filehandle="<<file<<endl;
	// cout<<" first g ="<<file.tellg()<<endl;
	// file>>a;
	// cout<<" second g ="<<file.tellg()<<endl;
	
	file.getline(ss,200); cout<<"  descryption line : "<< ss<<"\n" ; 
	file>>a; int degree=a;
	double c;
	cout << "polynomial degree="<<degree<<"\n";
	while (file>>a){
		file>>c;
		switch (a){
			case 0: c0=c; break;
			case 1: c1=c; break;
			case 2: c2=c; break;
			case 3: c3=c; break;
			case 4: c4=c; break;
			default: cout<<" invalid degreee found in file!\n";
		}
		cout <<" at degree="<<a<<"   coef="<<c<<"\n";
	} 
	file.close();

	return 0;	
	
	
	
//writing to file
	file.open("writingfile.txt", fstream::in | fstream::out | fstream::trunc);
	cout <<"\n\n\n WRITING DATA TO FILE  filehandle="<<file<<endl;
	for (int i=0;i<10;i++){
		file<<"writing now "<<i<<"\n";
	}
	file.close();
	
	
	
	return 0;
		
}