Nested Loop Help

[quayda]

So, I've written part of this program, basically just gathering all the info so far. But, I need the program to now calculate, and calculate on an interval. How do I do this with a nested loop? Am I on the right track with the for loop?

Thanks very much for any input.

#include <iostream>
#include <iomanip>
#include <stdio.h>
using namespace std;
          
// Define constants.

#define a 3.952
#define b 0.0427
#define R 0.08206
#define mL_L .001

int main ()
{
	float moles;			//IN: Number of moles of CO2 (n).
	float temp;			//IN: Temperature (K).
	float initial;			//IN: Initial volume (mL).	
	float final;			//IN: Final volume (mL).
	float increment;		//IN: Increment volume (mL) b/w lines of the table.
	float pressure;			//OUT: Pressure (atm).
	float loopVol;			//Variable assignment for loop function.
	float volume;			//Variable assignment for calculations.
	
	//Request user input.
	
	cout << "\nEnter the quantity of Carbon Dioxide (moles): ";
	cin >> moles;
	cout << "\nEnter the Temperature (K): ";
	cin >> temp;
	cout << "\nEnter the Initial Volume (mL): ";
	cin >> initial;
	cout << "\nEnter the Final Volume (mL): ";
	cin >> final;
	cout << "\nEnter the Volume Increment (mL): ";
	cin >> increment;
	
	//Set for table.
	
	cout << "\n\nVolume (mL)                    Pressure (atm)" << endl;
	
	//Begin calculations.
	
		for(loopVol = initial; loopVol <= final; loopVol += increment)
			{
			printf("  %.2f", loopVol);
			volume = loopVol * mL_L;
			pressure = (moles * R * temp)/(volume - b * moles) - (a * moles * moles)/(volume * volume);
		
			printf("                             %.4f",pressure);		
			} while (loopVol <= final);
		
		return 0;
}

[dhayden]

The "while" part of your code doesn't do anything by the way. Your code will be interpreted like this:

for(loopVol = initial; loopVol <= final; loopVol += increment)
{
	printf("  %.2f", loopVol);
	volume = loopVol * mL_L;
	pressure = (moles * R * temp)/(volume - b * moles) - (a * moles * moles)/(volume * volume);
	
	printf("                             %.4f",pressure);		
}

while (loopVol <= final)
	;

In other words the code contains a "for" loop and then a "while" loop. By the time the "while" loop executes, loopVol will be greater than "final" because if it wasn't, then the "for" loop would still be executing.

A "for" loop is really just shorthand for a "while" loop. Any "for" loop like this:

for (a; b; c) {
   code;
}

is equivalent to this:

{
	a;
	while (b) {
		code;
		c;
	}
}

Hope this helps. If you're still having trouble then explain what you're trying to compute.

[quayda]

Wow, thanks. That helped a lot! Now, I'm just having trouble having the results print in a tabular form. They're printing in a strange space array. But, I'm not sure how to do either of the following which I think would fix the issue:

(a) use setw in conjunction with printf
(b) change to cout to use setw, but still retrieve previous answers

Am I over-complicating the process?