//CSC099 Individual Assignment
//Name : MUHAMMAD IRFAN TIJANIE BIN MOHAMMAD TASNIM
//STUDENT ID : 2019273078
//GROUP : PI009E34

#include <stdio.h>
void realgas(float,int);
void display(int,float);
#define a 3.592			//co2 van der walls constant
#define b 0.0427
#define r 0.08206		//gas constant

int main()				//main fn
{
	float mole;
	int temp;
	char choice;
	do	{
		do{
			printf("Mole: ");
			scanf("%f", &mole);
			if(mole<=0)							//reenter if mole<=0
			printf("Invalid Input . Please enter Positive value\n\n");	
			}
			while(mole<=0);
		do{
			printf("Temperature (Kelvin): ");
			scanf("%d", &temp);
			if(temp<=0)							//reenter if temperature<=0
			printf("Invalid Input . Please enter Positive value\n\n");
			}
			while(temp<=0);
		realgas(mole, temp);
		do{
			printf("\n\n\nDo you want to continue (Y,y-Yes, N,n-NO): ");
			scanf(" %c", &choice);
			if(choice!='Y'&&choice!='y'&&choice!='N'&&choice!='n')	//reenter if invalid input
			printf("Invalid Input. Please enter Y,y or N,n\n");
			}
		while(choice!='Y'&&choice!='y'&&choice!='N'&&choice!='n');
		
		printf("-------------------------------------------------------------\n");
			}
	while(choice=='Y'||choice=='y');
	printf("From this calculation, you know that when volume (ml) in increasing,\npressure of gas reduce\n\nThank you");
}

void realgas(float mole, int temp)		//calculation fn
{
	int i_vol,f_vol,inc,dec;
	float ps;
	
	do{									//repeat if negative
		printf("Initial volume (milliliter): ");
		scanf("%d", &i_vol);
		if(i_vol<=0)		//display error 
		printf("Invalid Input . Please enter Positive value\n\n");
		}
	while(i_vol<=0);
	
	do{									//repeat if negative
		printf("Final volume(): ");
		scanf("%d", &f_vol);
		if(f_vol<=0)						//display error
		printf("Invalid Input . Please enter Positive value\n\n");
		}
	while(f_vol<=0);
	
	if(i_vol<f_vol){					//user enter increment/decrement
		do{
			printf("Increment : ");
			scanf("%d", &inc);	
			if(inc<=0)					//reenter if increment<=0
			printf("Invalid Input . Please enter Positive value\n\n");
			}
		while(inc<=0);
		}
	else {	
		do{
			printf("Decrement : ");
			scanf("%d", &dec);		
			if(dec<=0)					//reenter if decrement<=0
			printf("Invalid Input . Please enter Positive value\n\n");
			}
		while(dec<=0);
		}
	
	printf("\n\n%.4f moles of carbon dioxide at %d kelvin\n\n\n", mole, temp);
	printf("Volume (milliliter)\t Pressure(atm)\n");
	
	if(i_vol<f_vol)
	{	do{
			ps=(mole*r*temp)/(i_vol*0.001-(mole*b))-((a*mole*mole)/(i_vol*0.001*i_vol*0.001));
			display(i_vol,ps);		//fn call
			i_vol+=inc;
		}	
		while(i_vol<=f_vol);
	}
	
	else
	{
		do{
			ps=(mole*r*temp)/(i_vol*0.001-(mole*b))-((a*mole*mole)/(i_vol*0.001*i_vol*0.001));
			display(i_vol,ps);		//fn call
			i_vol-=dec;
		}
		while(f_vol<=i_vol);
	}
	
}

void display(int vol,float ps)			//display fn
{
	printf("%d\t\t\t %.4f\n", vol, ps);		//show in tab
}