void functions

[illingas]

hello! for an assignment we have to use void and value returning functions.
we have to calculate the metabolic power of an animal. here is my program:

#include <iostream>
using namespace std;

void GetData(double &, double &, double &, double &, double &, double &);
double CalcVoc (double, double, double);
double CalcSTP (double, double, double);
double CalcMP (double, double);
void PrintMetPow (double, double, double, double, double, double, double);

int main ()
{
double mass;
double aT;
double cP;
double pre;
double post;
double vaf;
double stp;
double mp;
double voc;

GetData (mass, aT, cP, pre, post, vaf);

voc = CalcVoc (vaf, pre, post);

stp = CalcSTP (voc, vaf, aT);

mp = CalcMP (stp, mass);

PrintMetPow (mass, aT, cP, pre, post, vaf, mp);

return 0;
}

void GetData (double & mass, double & at, double & cP, double & pre, double & post, double & vaf)
{
cout << "Please input the mass of the animal: ";
cin >> mass;
cout << "Please input the ambient temperature: ";
cin >> at;
cout << "Please input the chamber pressure: ";
cin >> cP;
cout << "Please input concentration of oxygen in ambient air (pre-animal): ";
cin >> pre;
cout << "Please input concentration of oxygen in ambient air (post-animal): ";
cin >> post;
cout << "Please input the rate of oxygen: ";
cin >> vaf;
}

//This is suppose to be a void function but i dont understand how that will work?
double CalcVoc (double vaf, double pre, double post)
{
double voc = vaf * (pre - post) / (1 - post);
return voc;
}

double CalcSTP (double voc, double cp, double at)
{
double stp = voc * (cp / 760) * (273 / (273 + at));
return stp;
}

double CalcMP (double stp, double mass)
{
double mp = stp / (mass * 0.179);
return mp;
}

void PrintMetPow (double mass, double at, double cp, double pre, double post, double vaf, double mp)
{
cout << "The mass of this animal is " << mass << " grams" << endl;
cout << "The ambient temperature is " << at << " degrees" << endl;
cout << "The chamber pressure is " << cp << " mmHG" << endl;
cout << "The concentration of ambient air (pre-animal) is: " << pre << endl;
cout << "The concentration of ambient air (post-animal) is: " << post << endl;
cout << "The rate of oxygen is: " << vaf << endl;
cout << "The metabolic power for this mammal or reptile is: " << mp << endl;
}


for CalcVoc it is suppose to be a void function. I used a value returning function, i dont understand how you would get the numbers for voc using a void function? thanks in advance!!

[Warnis]

The same as for getData, you send the value you want assigned as a reference

[illingas]

oohhhh thank you so much!

[illingas]

i have another question

Step 3. Correct voc to standard temperature and pressure (stp).
stp = voc * (cp / 760) * (c1 / (c1 + at)),

where c1 is the constant value 273 for correcting from voc to stp.

Step 4. Calculate metabolic power (mp) from stp.
mp = stp / (mass * c2),

where c2 is the constant value 0.179 for calculating mp from stp.


those are the formulas we are suppose to use.. i didnt understand what c1 and c2 is so i just put 273 in for c1 and 0.179 for c2

double CalcSTP (double voc, double cp, double at)
{
double stp = voc * (cp / 760) * (273 / (273 + at));
return stp;
}

double CalcMP (double stp, double mass)
{
double mp = stp / (mass * 0.179);
return mp;
}


i dont think this is correct but i dont know what else to do. Any ideas?

[Slambofett]

Not quite sure what you are wanting, if you just want to use c1 and c2 instead of 273 and 0.179 then you could use.

#define c1 273
#define c2 0.179

or

const int c1 = 273
const float c2 = 0.179

[Warnis]

(Avoid defines btw)

[illingas]

hmm hmm hmm.. ya well if i do that it doesnt give me the right answer, but its okay thanks anyways ill just ask the teacher :)